International Power and Standards Conversion

Version 1.12a (02-Dec-06)

Copyright © 1994-2014
Samuel M. Goldwasser
--- All Rights Reserved ---

For contact info, please see the
Sci.Electronics.Repair FAQ Email Links Page.


Reproduction of this document in whole or in part is permitted if both of the following conditions are satisfied:
  1. This notice is included in its entirety at the beginning.
  2. There is no charge except to cover the costs of copying.


Table of Contents



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    Preface

    Author and Copyright

    Author: Samuel M. Goldwasser

    For contact info, please see the Sci.Electronics.Repair FAQ Email Links Page.

    Copyright © 1994-2014
    All Rights Reserved

    Reproduction of this document in whole or in part is permitted if both of the following conditions are satisfied:

    1.This notice is included in its entirety at the beginning.
    2.There is no charge except to cover the costs of copying.

    DISCLAIMER

    While every effort has been made to assure that the information in this document is accurate and complete, there is no way to guarantee that it will apply to your particular equipment. Depending on the specific design, what works in most cases may result in unacceptable performance, blown fuses or tripped circuit breakers, or overheating and possible fire, damage to the powered equipment or property.

    We will not be responsible for improper operation, equipment or collateral damage, or expenses resulting from following the suggestions contained herein.



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    Introduction

    Scope and Purpose of this Document

    The following types of questions arise quite often: We cannot generally provide an answer based on your exact model equipment and the specific standards in use. There are too many variations to deal with in this sort of document. However, the information contained herein in conjunction with the type and specifications of the equipment you own and the power and standards in use at your destination hsould enable you to make an informed decision. Note that if you plan to be moving between countries with different standards, it may pay to invest in appliances and electronic specifically designed for multisystem operation. However, there are all sorts of definitions of 'multisystem' - not all will handle what you need so the specifications must be checked carefully and even then, marketing departments sometimes get in the way of truth in advertising! Again, the information in this document and the links below should aid in this effort.

    Related Information

    A great deal of specific country information is available at: including power, plug configurations, telephones, and TV standards.

    This should help you issues involved before you reach your destination!

    Panel Components - Guide to Worldwide Plug/Socket Patterns and Power Mains has information and photos.

    In addition, we deal with general issues related to adapting entertainment equipment and appliances to different power and the implications of reduced or increased voltage and frequency.

    Note: this initial release will concentrate mostly on power issues. Later, we will deal with video, communications, and phones systems. For those, the documents: Notes on Video Conversion, Troubleshooting and Repair of Computer and Video Monitors, Troubleshooting and Repair of Television Sets, and Troubleshooting and Repair of Video Cassette Recorders, and others at this site may contain some of the information you seek on these other topics.



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    Types of Conversion

    You Mean it is More Than Just the Type of Plug?

    It would be nice if all you had to do was match up a plug and socket to make anything in the universe work together. Unfortunately, while this does work for some things - garden hoses, for example :-) - it rarely is as simple as this for electrical power, video, or communications.

    Power Conversion

    This relates to what comes out of the wall socket. Nearly every country in the world uses an AC voltage between 90 and 240 V at 50 or 60 Hz. There may be some exceptions (like 600 V at 25 Hz powering portions of the New York City subway system or 28 V at 400 Hz on board an F-18 - but this is not something you are likely to need to deal with!) - if you encounter such unusual situations, we will be happy to add them to this document!

    The three important considerations are:

    Video Standards Conversion

    This relates to the scan rates, color encoding, and audio transmission of the baseband video signals in use in your country.

    Broadcast (and Cable) Standards



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    Voltage Conversion Issues and Common Types of Voltage Converters

    How to Get Power for Equipment A to Work with Equipment B

    There are a variety of approaches to adapting equipment designed for one power system to another.

    Note that in cases, the proper (or close enough) power may be available already.

    True Transformers

    This refers to devices that consist solely of a pair (at least) of windings on an iron core. There are no other devices in a transformer beyond possibly a switch, indicator light, thermal protector, and/or a fuse or circuit breaker, and a plug or terminal block for input and socket or terminal block for output.

    In the following, we assume that the two voltages are 110 VAC and 220 VAC. Similar comments apply if the ration is not 2:1.

    There are several types including:

    Autotransformers are cheaper but do not provide line isolation which may be desirable. In general, a step-up or step-down transformer can be used backwards to effect the opposite conversion - whether this is possible is a construction detail. In addition, a 1:1 isolation transformer can be used as a 1:2 (stepup) or 2:1 (stepdown) autotransformer with a VA rating twice of what it would be when used normally.

    The relevant parameters characterizing a tansformer consist of:

    Transformers of adequate capacity can be used with all types of equipment.

    However, they are heavy and costly and do not convert frequency. Thus, they may be unsuitable in some situations and there may be cheaper more appropriate alternatives. A *suitable* transformer large enough to power a space heater would weigh about 50 pounds and cost perhaps $200 - much more than the the space heater is worth.

    Using a Low Voltage Transformer to Increase or Reduce Line Voltage

    Sometimes, it is only necessary to adjust the voltage by 10 or 20 V to be fully compatible. For example, this might be the case when using domestic Japanese gear in the U.S. and vice-versa. Their line voltage is closer to 100 VAC compared to our 115 VAC.

    An easy way to change the voltage by 15 V (for example) up or down, is to obtain a transformer with a 110 V primary and around a 15 V secondary. The secondary current rating needs to be at least equal to the load requirements. Wire it up so the secondary is in-phase in series with the AC to the load to boost voltage (as shown below) or out-of-phase to reduce it.

    Note: To obtain exactly the correct voltage will require a slightly higher or lower voltage transformer than this simple explanation would indicate since the input voltage will be slightly lower or higher than the transformer's rated input voltage. This is usually not an issue since precise voltage to an appliance or piece of electronic equipment is generally not required.

    
                                 +------------+
                                 |            |
                   AC In o-------+--+         |
                                   o )|| +----+
                                     )||(
              105 VAC Line   Primary )||( Secondary
                                     )||( o
                                     )|| +---------o AC Out
                   AC In o-------+--+
                                 |                          120 VAC to Load
                                 +-----------------o AC Out
    
    

    Thyristor Based Converters

    These are the low cost devices available at Radio Shack or a travel accessories store that weigh almost nothing and have huge power ratings. They operate by switching the power on to the load at the appropriate time during each cycle of the AC voltage (120 or 100 times a second) resulting in approximately the proper power being delivered to the load.

    Thyristor based converters are for converting from 220 VAC to 110 VAC without changing frequency with major restrictions:

    Since all a thyristor (triac) can easily do is turn on - it has to wait until the end of the cycle to turn off - to get the same effective power from a 220 VAC input as a 110 V input will require a higher peak voltage with a duty cycle of much less than 100 percent. Capacitors in the power supply of typical electronic like to charge to the peak - BLAM! The high peak voltage can result in breakdown of underrated insulation and have other undesirable effects on devices like induction motors and transformers. Even equipment for which these are supposedly designed can be destroyed or may represent a safety risk since there can be much higher voltages inside than normal.

    Motor Alternators

    Before the development of solid state power devices, these represented an efficient, if bulky way of converting both voltage and frequency. A synchronous induction motor is coupled to an alternator (AC generator) on the same shaft. By designing with the appropriate number of poles for each, this could easily, if noisily, perform both voltage and frequency conversion.

    Solid State (AC->DC->AC) Converters

    These provide efficient conversion of both voltage and frequency in a light weight compact package. The best of these generate an output nearly identical to the power obtained from the wall socket and operate as follows: The waveform before smoothing would look similar to the following:
                         ||                  ||              
                       ||||||              ||||||            
                      ||||||||            ||||||||           
                     ||||||||||          ||||||||||         
                     ||||||||||          ||||||||||          
                               ||||||||||          ||||||||||
                               ||||||||||          ||||||||||
                                ||||||||            ||||||||
                                 ||||||              ||||||            
                                   ||                  ||
    
    After smoothing, the result would be very similar to a sinusoid.

    This more costly approach enables arbitrary voltage *and* frequency conversion but as we will se later, this is rarely needed. For an idea of how to design such a converter, see the section: Design of High Efficiency Power Inverters.

    Cheaper models simply generate a square wave or modified sinewave at the appropriate frequency:

    Squarewave:

                      _________           _________
                     |         |         |         |          
                     |         |         |         |          
                     |         |         |         |          
                     |         |         |         |          
                               |         |         |         |
                               |         |         |         |
                               |         |         |         |
                               |_________|         |_________|
    
    Modified sinewave:
                         _____                 _____  
                        |     |               |     |         
                        |     |               |     |         
                        |     |               |     |         
                     ___|     |____       ____|     |____          
                                   |     |               |    |
                                   |     |               |    |
                                   |     |               |    |
                                   |_____|               |____|
    
    The nice thing about the modified sinewave is that its RMS and peak values match that of the true sinusoid (as well as other advantages in terms of harmonic content). If you don't know what this means, don't worry, Your life doesn't depend on it. One implication, however, is that heating loads and electronic devices which rectify and filter the input power will see the same effective voltage.

    For many devices including all resistive loads, either of these approaches is adequate. However, devices with motors and/or transformers will be much happier with smoothed sinusoidal power. Switching power supplies (except universal types) will be underpowered with the simple squarewave inverter and may overheat running near full load.

    Design of High Efficiency Power Inverters

    Here is a general recipe - season to taste. :) (From: James Meyer (notjimbob@earthlink.net).)
    1. Make a DC to DC converter using any one of several standard designs available almost anywhere. Pick a design using switch-mode control and a high frequency transformer. The input voltage you already know. Make the output voltage adjustable over a 0 to 170 volt range by way of a low-level input signal of maybe 0 to 10 volts. The output current will be whatever you want for the 120 volt AC output current. You'll probably want to have a transformer in there to isolate the output from the input, but it will be a small one because the frequency will be very much higher than 60 Hz.

    2. Build a signal generator that puts out a 0 to 10 volt signal that looks like a half-wave rectified 60 Hz waveform. Use that to control the DC to DC converter.

    3. Then use an H-bridge switch on the output of the 0 to 170 volt converter to get alternate plus and minus output. Use a square wave that changes state at each 0 volt output point of the input signal to drive the H-bridge.
    Using this approach, you can step the input voltage up to the peak of the sine wave that you want at the output with a decent converter that can be very efficient and produce little waste heat.

    The H-bridge MOSFETs are also only switches so they can be efficient. Plus, you're switching currents at the output voltage level which is a lot smaller than the current at the DC input.

    You'll get a sine wave at the output and the whole thing should be simple and fairly cheap. The high frequency switching converter will be the hardest part to get going because of the wide adjustable output voltage range required, but I think it will still be easier than the "brute force" method.

    Some Power Converter Companies Here are a few random companies that offer power converters. I am in no way endorsing their products and have no direct knowledge of their quality or performance. Listed in alphabetical order.

    What Appliances will be Damaged by Reduced Voltage?

    Here is a summary of various appliance types and how they are affected by the severely reduced voltages possible during a brownout: For appliances with more than one type of device like a microwave oven, all factors must be considered. For this example, the oven will heat at a reduced power level (which is safe) but the cooling fan(s) will also run more slowly resulting in possible overheating and failure of the magnetron. A convection space heater may overheat for similar reasons.

    How Big a Difference in Voltage Before a Converter is Needed

    "I would like to bring a variety of small to medium-sized Japanese electrical products (100V 50/60 Hz) with me when I move back to the U.S. (e.g., lights, rice-cooker, cassette player, VCR...) Individual transformers like those sold in travel shops are quite expensive. Is it possible buy a large number of small stepdown transformers -- or to make them as kits? Any advice would be greatly appreciated."
    First, for some of these like the VCR, the 15% difference between 115 VAC and 100 VAC may not matter. The only way to be sure is to check with the manufacturer.

    For others like the rice cooker, it too may be ok if it uses a thermostat to control its heating element.

    However, the simplest way to reduce 115 to 100 VAC is to buy or construct an autotransformer.

    To construct one, you need a stepdown transformer with an output of about 15 V (for this example) and a secondary current rating at least equal to your total current needs. Then, the primary is connected to the line and the secondary is wired anti-phase in series with the loads and the line.

    For devices using AC adapters, I would just replace the AC adapters with a US version.

    Effects of Improper Voltage on Resistive Loads

    Effects of Improper Voltage on Constant Power Loads

    Effects of Improper Voltage on Transformer Loads

    While the ideal transformer (the one they may have taught you about in EE101) doesn't care about its actual input voltage, real transformers do. If the voltage increases significantly above what it was designed for, the core may saturate. This means that the magnetic field in the core cannot increase any further and the result is to effectively short circuit the input (above a certain voltage on the waveform). At the very least, this will result in excessive heating and hum or buzz. The transformer may burn out if a fuse doesn't blow first.

    How much excess voltage is acceptable is not something that can be determined without testing. Some transformers are designed very conservatively (bigger cores, more copper, etc.) while others just barely get away with running on the nominal line voltage.

    Certainly, 2:1 will be too much for almost any transformer. You may get away with a 25% increase without too many problems.

    It is possible to test for this by slowing increasing the input voltage while monitoring input current. Up until saturation, it will increase linearly with voltage. As saturationg sets in, a small increase in voltage will result in a large increase in current and increased buzz or hum as well.

    Reducing voltage to a transformer is not a problem unless the load will then demand more current - which may result in excessive heating and failure.

    Effects of Improper Voltage on Motor Loads



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    Line Frequency (50/60 Hz) Issues

    Is Frequency Conversion Needed?

    The question of 50 Hz vs. 60 Hz always comes up in conjunction with international power. However, except for equipment with induction motors (e.g., fans, compressors), or where the line frequency is used for timing (electric or line powered electronic clocks), the line frequency may be irrelevant.

    Effects of Improper Frequency

    Equipment that Will Probably not Care About the Line Frequency

    The following are generally insensitive to frequency (50/60 Hz):

    However, note different TV standards will likely result in your TV and VCR working together but not able to receive or record broadcasts or cable.

    Some equipment explicitly states the acceptable voltage and frequency range. In the case of a universal power adapter, this may range from 90 to 260 V DC or AC up to 400 Hz - or more.

    Equipment that May Work with a Different Line Frequency

    The following will probably work when going from 50 Hz power to 60 Hz power and may work going the other way. However, transformer cores designed for 60 Hz may saturate on 50 Hz and run hotter and/or blow internal fuses and cooling fans will run slower - this should be checked to make sure there is no hazard:

    Equipment that May have Problems on Different Line Frequency

    The following may have problems:



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    Recommendations for Specific Equipment

    General Considerations

    The sections below summarize the major issues with respect to common appliances and consumer electronic equipment. Following these are those which relate specifically to moving overseas or vice-versa.

    Television Sets and Video Cassette Recorders

    A voltage converter - preferably a true transformer or modified or true sinewave inverter will be needed to adapt the voltage unless the unit has a universal power supply.

    Modern TVs do not care about power line frequency at all as they do not have any power transformer. Really old sets may run into core saturation problems but these are mostly dead by now.

    Note: the video frame rate is not tied to the power line in any way. Therefore, a U.S. TV with a 60 Hz (actually 59.94 Hz) frame rate will work just fine in a country with 50 Hz power assuming the voltage is correct. However, it will not be compatible with broadcast or cable or likely a VCR purchased in that country - see below.

    VCRs may use a small power transformer in the power supply so changing from 60 Hz to 50 Hz may result in overheating though probably not likely.

    However, taking a VCR and TV from the U.S. to a European country, for example, may not be worth it. They will work fine with each-other (as long as the voltage is proper) but the video standards in foreign countries are not compatible with those in the U.S. Therefore, it may be better to buy new equipment overseas unless you are taking your prized collection of videos and will obtain other equpiment to deal with broadcast and cable. There are also services for copying video cassettes from one standard to another and these may represent an alternative to lugging the equipment with you.

    Small Appliances

    Specific recommendations will depend on the actual devices inside the appliance - motors, heating elements, timers, and so forth.

    Clocks

    Electric clocks using a synchronous motor would require a motor or gear transplant - not worth it. Of course, you could just live with shorter or longer days :-).

    Clocks using the power line to drive an electronic display may have a jumper to select 50 or 60 Hz. Even this may not be worth the effort to locate as it is likely not going to be labeled.

    Fluorescent Lamps

    For those using iron ballasts, both voltage and frequency will be significant. Though it may be possible to come up with a formula which incorporates both, the best thing to do is to only use the line voltage for which the unit was designed.

    Where the frequency isn't the same, the current through the lamp may differ, most likely too high in going from 60 Hz to 50 Hz, too low the opposite way. If the current is too high, there could be shortened lamp life at the very least or even a serious fire hazard. If the current is too low, the lamp may not remain on in a stable manner, flickering, or constantly restarting. Initial starting could also be affected.

    If they use electronic ballasts, the frequency probably won't matter. Some "universal" types, can accommodate an input voltage from 90 to 250 VAC up to 400 Hz or even DC.

    In all cases, it is best to consult with the manufacturer if the product label doesn't explicitly indicate "50/60 Hz" operation. When in doubt, leave them behind since there is really no way to be sure of the safety issues.

    Audio Equipment

    These include tuners, amplifiers, receivers, tape decks, CD players, etc.

    Except for the tuner or tuner portion of the receiver, the only issue is power. Audio equipment almost always uses a transformer type power supply so the comments in the previous chapters should apply. A voltage converter will be needed to go from 110 VAC to 220 VAC or vice-versa. In this case, it really should be a true transformer. Anything else is quite likely to introduce unaccceptibel interference in the form of a hum or buzz even if it doesn't result in any damage to the equipment. As noted, going from 60 Hz to 50 Hz could intruduce problems of transformer core saturation in marginally designed equipemnt as well.

    Radios, Tuners, Receivers

    In addition to the power issues (see the section: Audio equipment, station frequencies and channel spacing differ from country to country.

    Microwave Ovens

    If the voltage is different, sell where you are located and buy a new one at your destination. The power involved would require a large, heavy, expensive voltage converter - preferably a true transformer. It doesn't make sense for a $150 microwave.

    Line frequency doesn't affect the performance of a microwave that much (perhaps a 5 percent increase in cooking power from 50 Hz to 60 Hz) but the timer and clock will likely be affected and may not be easily adjusted - not at all in the case of a mechanical timer though there may be a jumper for an electronic timer. However, the turntable and cooling fan motors will also be affected and attempting to account for all the variations is probably just not worth it!

    PCs and Laptop/Notebook Computers

    Check your equipment. Most PC power supplies have a switch to select between 110 VAC and 220 VAC. Some have universal power supplies that will work within a range of voltage between 90 and 240 V AC (up to 400 Hz) or DC. The latter is generally true of laptop/notebook power packs.

    Similary, monitors may use a switch or jumper to select voltage or have a universal power supply.

    PCs and monitors do not use the line frequency for anything - not even the real time clock.

    Laser Printers

    These may use a switching or transformer based power supply. This is not the real problem. What is, is the power for the fuser - several hundred watts. Therefore, if using a true transformer for voltage conversion, a large one will be required.

    Some may have universal power supplies - check your instruction manual!

    Non-Laser Printers

    These will usually use a power transformer type power supply so a voltage converter will be needed. The frequency will only matter with respect to transformer core saturation. Nothing in a printer depends on line frequency.

    Taking Equipment Overseas (or Vice-Versa)

    When does it make sense to take an appliance or piece of electronic equipment to a country where the electric power and possibly other standards differ?

    For anything other than a simple heating appliance (see below) that uses a lot of power, my advise would be to sell them and buy new when you get there. For example, to power a microwave oven would require a 2kVA step down (U.S. to Europe) transformer. This would weigh about 50 pounds and likely cost almost as much as a new oven.

    Note that some places like Japan may even have varying power specifications in different parts of the country. Isolated areas such as islands may have their own power generators with very erratic and voltage and frequency. The following discussion assumes power from a large (national) grid.

    There are several considerations:

    1. AC voltage - in the U.S. this is nominally 115 VAC but in actuality may vary from around 110 to 125 VAC depending on where you are located. Many European countries use 220 VAC while voltages as low as 90 or 100 VAC or as high as 240 VAC (or higher?) are found elsewhere.

    2. Power line frequency - in the U.S. this is 60 Hz. The accuracy, particularly over the long term, is excellent (actually, for all intents and purposes, perfect) - better than most quartz clocks. In many foreign countries, 50 Hz power is used. However, the stability of foreign power is a lot less assured.

    3. TV standards - The NTSC 525L/60F system is used in the U.S. but other countries use various versions of PAL, SECAM, and even NTSC. PAL with 625L/50F is common in many European countries.

    4. FM (and other) radio station channel frequencies and other broadcast parameters differ.

    5. Phone line connectors and other aspects of telephone equipment may differ (not to mention reliability in general but that is another issue).

    6. Of course, all the plugs are different and every country seems to think that their design is best.
    For example, going to a country with 220 VAC 50 Hz power from the U.S.:

    For electronic equipment like CD players and such, you will need a small step down transformer and then the only consideration power-wise is the frequency. In most cases the equipment should be fine - the power transformers will be running a little closer to saturation but it is likely they are designed with enough margin to handle this. Not too much electronic equipment uses the line frequency as a reference for anything anymore (i.e., cassette deck motors are DC).

    Of course, your line operated clock will run slow, the radio stations are tuned to different frequencies, TV is incompatible, phone equipment may have problems, etc.

    Some equipment like PCs and monitors may have jumpers or have universal autoselecting power supplies - you would have to check your equipment or with the manufacturer(s). Laptop computer, portable printer, and camcorder AC adapter/chargers are often of this type. They are switching power supplies that will automatically run on anywhere from 90-240 VAC, 50-400 Hz (and probably DC as well).

    Warning: those inexpensive power convertors sold for international travel that weigh almost nothing and claim to handle over a kilowatt are not intended and will not work with (meaning they will damage or destroy) many electronic devices. They use diodes and/or thyristors and do not cut the voltage in half, only the heating effect. The peak voltage may still approach that for 220 VAC resulting in way too much voltage on the input and nasty problems with transformer core saturation. For a waffle iron they may be ok but not a microwave oven or stereo system. I also have serious doubts about their overall long term reliability and fire safety aspects of these inexpensive devices..

    For small low power appliances, a compact 50 W transformer will work fine but would be rather inconvenient to move from appliance to appliance or outlet to outlet. Where an AC adapter is used, 220 V versions are probably available to power the appliance directly.

    As noted, the transformer required for a high power heating appliance is likely to cost more than the appliance so unless one of the inexpensive convertors (see above) is used, this may not pay.

    CD Players

    Fortunately, the standard for the CDs themselves is the same everywhere in the explored universe Yes, even Australia :-). Thus, there should be no issues of incompatibility. The differences will relate only to the power supply.

    First, check your user's manual (which you of course have saved in a known location). It may provide specific instructions and/or restrictions.

    Most component type CD players use a simple power supply - a power transformer followed by rectification, filter capacitors, and linear regulators. These will usually only require a small step up or step down transformer to operate on a different voltage. Since power requirements are minimal, even a 50 VA transformers should be fine. WARNING: never attempt to use one of those cheap lightweight power adapters that are not true transformers to go from 220 V to 110 V as they are designed only for heating appliances. They will smoke your CD player (or other equipment not designed to handle 220 V to 240 V input).

    Some CD players may have dual voltage power transformers which can be easily rewired for the required voltage change or may even have a selector switch on the rear panel or internally.

    The frequency difference - 50 or 60 Hz should not be a problem as nothing in a CD player uses this as a timing reference. The only slight concern would be using a CD player specified for 60 Hz on 50 Hz power - the transformer core may saturate and overheat - possibly blowing the internal fuse. However, I don't really think problems are likely.

    For portable CD players, if your wall adapter does not have a voltage selector switch, obtain one that is rated for your local line voltage or use a suitable transformer with the one you have. As with power transformers, a frequency difference may cause a problem but this is not likely.

    Microwave Ovens

    Microwave ovens are high power appliances. Low cost transformers or international voltage adapters will not work. You will need a heavy and expensive step down or step up transformer which will likely cost as much as a new microwave oven. Sell the oven before you leave and buy a new one at your destination.

    Furthermore, for microwave ovens in particular, line frequency may make a difference. Due to the way the high voltage power supply works in a microwave oven, the HV capacitor is in series with the magnetron and thus its impedance - which depends on line frequency - affects output power.

    High voltage transformer core saturation may also be a problem. Even with no load, these may run hot even at the correct line frequency of 60 Hz. So going to 50 Hz would make it worse - perhaps terminally - though this is not likely.

    The digital clock and timer will likely run slow or fast if the line frequency changes as they usually use the power line for reference. Of course, this may partially make up for your change in output power! :-)

    Buying a TV in Europe

    "I have the following question for you specialists:

    Can I buy a TV in any west-european country and use it in any other west European country? For example, buying a TV in the Netherlands and use it in Greece or buying in France and using in England.

    Any help would be appreciated as I do not really trust the sale people at the store."

    Neither would I.

    Along with the multiple audio/video formats, there may be differences in channel frequency assignments between the various countries.

    Channel 5 in country X may not be on the same actual frequency as Channel 5 in country Y or Z. The channel spacings or modulation may also be different.

    (From: Phil Nichols (in5379@wlv.ac.uk).)

    Plus, in different countries the audio signal can be transmitted at a different frequency relative to the vision signal. Great! Perfect picture, no sound!

    I believe most continental European countries use PAL B (narrow vision bandwidth; sound carrier 5.5MHz higher than vision carrier), whereas the UK and Ireland use PAL I (wider vision bandwidth; sound carrier 6MHz higher than vision carrier).

    The wisest thing is to decide which countries you are most likely to want to visit with your TV, find out what transmission system they use, then go looking for a TV which can use that/those system(s).

    Almost all TVs in west Europe are compatible (PAL-B/G), except Britain (PAL-I) and France (SECAM-L). Greece is also using SECAM, but on very few channels and not all the time.

    (From: Wolfgang Schwanke (wolfi@berlin.snafu.de).)

    This is correct, but maybe not the whole story.

    There are differences in the broadcast bands used. At least Italy uses different channel allocations than the rest of the PAL-B/G crowd. Germany uses frequencies on cable that are unused elsewhere, which only special tuners can get. Also, there are different methods for transmitting stereo sound (NICAM vs. analogue).

    New TVs nowadays (sold in Europe anyway) are often all-world-standard all-frequency-bands, because it's easier for the manufacturer to make a "one for all" set instead of having so many different designs for every country. But don't rely on it.

    (From Jeroen Stessen (Jeroen.Stessen@philips.com).)

    Oh boy, here goes another long story:

    PAL-plus is an attempt to extend the life-cycle of terrestrial PAL transmissions by including compatible wide-screen (16:9) transmissions. It is an advanced variant of the letterbox format, this means that when you receive a PAL-plus widescreen program on an older 4:3 receiver you will see black bars top and bottom. It was originally developed in Germany (university of Dortmund in cooperation with German terrestrial broadcasters and some setmakers). Later a large consortium of European and Japanese setmakers took over and finished the job. Strangely, the German broadcasters seem to use PAL-plus only very rarely.

    The PAL-plus standard comprises three extensions to the PAL-standard:

    1. Vertical helper. In order to compensate for the fact that 1/4 of the video lines are not used, which would deteriorate vertical resolution for the widescreen viewer, the missing vertical information has been coded into the black lines in a manner as to be nearly invisible on a 4:3 receiver (you see some dark blue). The 16:9 PAL-plus receiver combines 432 visible lines plus 144 helper lines into 576 new visible lines.

    2. Colour-plus. The PAL colour carrier is modulated in a slightly different way (making use of correlation between 2 fields) in order to give a cleaner Y/C separation in the PAL-plus receiver.

    3. Signalling bits from which the receiver can conclude whether the transmission is 4:3/16:9/PAL-plus and adapt the display format accordingly. The bandwidth of these bits is low enough to survive recording on a VHS recorder.
    In order to enable a poor-man's PAL-plus receiver, the standard permits using the mark "PAL-plus" if at least the vertical helper reconstruction is included. Colour-plus is optional, so you will find sets on the market with only half of the PAL-plus extension.

    PAL-plus may also be combined with teletext, ghost cancellation reference, digital Nicam stereo, VPS, PDC and what-you-have more. Theoretically it can be broadcast over a satellite channel too, but it was not designed for that and some aspects of a satellite channel do indeed give interesting technical problems.

    There are also sets marketed as "PAL-plus compatible". These are mostly widescreen sets without any PAL-plus processing at all, but they allow switching of the display format between 4:3 and 16:9. They may well do that automatically, based on the signalling bits.

    There are 2 methods for displaying a 4:3 letterboxed signal on a 16:9 display, without using the PAL-plus helper lines:

    1. Increase of the vertical deflection amplitude to display only the centre 432 lines.

    2. Vertical interpolation without using the helper, to convert 432 lines into 576 lines and display on a 576 lines display.
    Both modes may be called "movie expand". Only when you really convert to full-resolution widescreen will it be called "widescreen".

    And there are 4 methods for displaying a regular 4:3 signal on a 16:9 display (regular PAL, has nothing to do with PAL-plus):

    1. Decrease of the horizontal deflection amplitude, this gives black bars left and right.

    2. Horizontal interpolation, to convert N pixels to 3/4*N pixels. Both modes may be called "4:3" or "normal"

    3. Non-linear horizontal deflection waveform, called "Panorama mode" by JVC, works by increasing the S-capacitor value.

    4. Non-linear horizontal interpolation, called "Superwide" by Philips, works with an advanced sample-rate convertor.
    With both modes, the left and right edges of the picture will be stretched to fill the left and right bars, but the aspect ratio of the centre part of the picture will hardly be affected.

    Interesting, ain't it ?

    (From: Allan Mounteney (allan@amounten.demon.co.uk).)

    RE: Is there a TV set that covers international standards?

    The answer is YES.

    Reason I know is that I was with a company that made computers with TV-OUT for world wide use and wanted something that could show that the TV Out worked for various countries.

    This ONE and ONLY one we could find Three years ago came from Germany and covered PAL, SECAM and the American NTSC systems and came with a note that said from the time of making/selling that set it would not work in just one small country in South America. All features (including audio) were adjustable from the front panel menu and it was a Grundig 17" job. I am advised that there is a load of others on the market now.

    The company who seemed to know all about these international sets and gave us good service at that time was Andrew McCulloch Ltd in Cambridge UK. Phone: 44(0)1223-351825



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    Items of Interest

    TV, Shortwave, Power Worldwide

    (From: Mark Zenier (mzenier@netcom.com).)

    A book, "The World Radio TV Handbook" published by Billboard that covers TV, along with where all the world's shortwave radio transmitters are, and what sort of power comes out of the wall plug all around the world. It has a new edition each year and costs around $25 to $30.

    About the Vertical Scan Rate

    TVs never ever used the line frequency for vertical rate. The vertical rate is not even equal to line frequency, actually 59.94 Hz (NTSC). It was set originally to 60 Hz to minimize the visibility of interference between the deflection and power transformer. When NTSC added color, it changed to 59.94 Hz. And, TVs no longer have power transformers.

    Determining Unknown Connections on International Power Transformers

    Most likely, you can figure this out if you can identify the input connections.

    There will be two primary windings. Each of these may also have additional taps to accommodate various slight variations in input voltage.

    For the U.S. (110 VAC), the two primary windings will be wired in parallel. For overseas (220 VAC) operation, they will be wired in series. When switching from one to the other make sure you get the phases of the two windings correct - otherwise you will have a short circuit! It is best to test with a Variac so you can bring up the voltage gradually and catch your mistakes before anything smokes.

    An multimeter on the lowest resistance scale should permit you to determine the internal arrangement of any taps.

    With any luck, the transformer wiring will even be labeled on the case!

    Running Three-Phase Motors on Single-Phase Power

    This may be an issue if you picked up a South Bend lathe with a 10 foot bed at a garage sale for $1 or more realistically with professional shop equipment like large saws or planars.

    A three-phase motor will run on single-phase power once started - but at somewhat reduced output power (horsepower). The very simple approach (compared to complete conversion) is to just provide a means for starting. The motor will then run at the correct speed (assuming the line frequency is the same) but will not be able to develop full torque before stalling. Actually converting single-phase to three-phase will likely be more expensive than replacing the motor.

    There is some info at the Building a Phase Converter site.

    A Note on Voltage in Europe

    (From: Michael Salem (4ms2u$ms@michaels.demon.co.uk).)

    Until recently voltage in the UK was 240 VAC nominal, +- 6%. Voltage in most of the rest of Europe was 220 VAC. A few years ago voltages throughout Europe were harmonized to 230 VAC. This caused very little disruption; no change to power stations or distribution systems, no equipment problems caused by the change.

    Why so trouble-free?

    It was a politicians' change: Voltage didn't change at all (at least in the UK). The permissible voltage in the UK used to be between 226V and 253V (240+/-6%). It is now 230V -6% +10%; i.e., anything between 216V and 253V. The actual voltage is exactly what it always was, it's just called 230V. Presumably as power stations and distribution equipment age and are replaced the actual voltage will decrease; but I have certainly measured the maximum permissible 253V in June 2000.



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