Electrical Question 50Hz and 60Hz

Its not the cps its the voltage it runs on. All the hz or cps means is that on a uk mains it will run slower. In the old days of turntables and tape decks powered by synchronous motors you often had to change the pulley to compensate one way or the other, the motor was the same either way. The brushed motors if the same voltage is applied will probably not make much difference. However as I say, many countries use lower voltages at 60hz and if you bring them over here you will need some kind of transformer to run them without burning them out. The other way around they will lack power and revs but are not likely to burn out unless you stall them.

Brian

It primarily effects motors. Many will run faster on 60Hz than 50Hz so sometimes causing overload. Heaters, no difference.

Voltage differences are the ones to watch out for.

Also, it almost certainly won't affect electronic equipment with a power supply and low-voltage supply to motors (eg tape transport, record turntable, motors for turning CD etc), because power supplies, either within the appliance or external as for a laptop, can cope with either frequency (and often all voltages between 120 in USA and 220-240 in Europe.

Appliances that will be affected are those with mains-synchronous motors which will run 60/50 = 20% faster. Also (and I was gobsmacked to learn this) quite a lot of mains digital clocks (eg in cookers) sync off the mains frequency, not a quartz crystal. Hence the story a few weeks ago about mains clocks running too fast or slow (I forget which) because the mains in mainland Europe had not been constrained within the normal limits of +/- a tight tolerance, with no nett gain or loss over a 24-hour period.

Voltage difference is a killer: for a resistive load, a 120V appliance will use 4x power on 240V - unless you use a step-down transformer.

depends on the motor.

NT

Not quite true. Some American stuff is made to only work on 60Hz 110v ac and relies on either mechanical resonance at 60Hz or very marginal transformer/electromagnets that go into saturation on UK 50Hz mains. Those awful US razors heavily advertised round Xmas being an example.

My first job in industry was to work out why a particular US made colour monitor was inclined to catch fire from time to time in the UK. Answer the PSU had never been designed to cope with UK mains frequency and frame rates. It worked well enough when used intermittently that there were a lot of them installed before it showed up as a serious problem...

Everything Japanese is designed for either frequency since half the main island is on US generator kit and the other on British!

You can buy auto (or isolating) transformers to take UK mains down to appropriate US or Japanese voltages. I'd be wary of US kit powered on UK mains - their insulation standards are not really up to it either.

A motor designed for 50Hz will run faster but with less torque on 60Hz. It seldom has any problematic effect except on turntables and clocks.

A motor designed for 60Hz and cut to the bone on price (like some US kit often is) will die horribly on 50Hz mains since the magnetic cores wil saturate at around 18ms and become a restive load for 10% of the cycle.

US mains razors are particularly cheap and nasty designed only for 60Hz.

That's a good point. Equipment sold in Europe is more multi-standard than US equipment. My sister bought a multi-standard VCR (capable of recording as well as playing in both NTSC and PAL) before she left to live in the US for a while, because she'd found that multi-standard equipment is a lot harder to obtain over there. She wanted to be able to watch tapes of her favourite programmes that we sent her from the UK as well as to record US programmes.

There is a place near Chicago that specialises in multi-standard, multi-country AV equipment. If she needs it, I can dig the name out.

Anyone with more than a passing familiarity with US trade and commerce will know that most USians have no concept of "the rest of the world".

I've lost count of the number of websites that simply ask your state ...

Thanks for the help.

My cousin brought a synchronous clock from Canada to Europe. From that point onwards time seemed to drag :-)

Tsk, tsk!

All this misinformation about induction motors (synchronous or not) and

A basic lesson and some truths about running such motors designed for

If you're planning on using a 120v 60Hz induction motor on 50Hz supply, you simply need to reduce the voltage in the same ratio. The torque will remain the same although you will obviously lose 20% power capability (and an increased risk of on load stalling if the motor rating was marginal to begin with).

Going the other way, you'll need use a 120 to 288 volt 60Hz step up transformer to power a 240v 50Hz motor if you wish to maintain the torque output at the higher speed or else accept a lower maximum torque output if merely doubling up the 120v to 240v - not always advisable if the torque rating of the motor is marginal to begin with.

For record players and tape decks that rely upon the mains frequency to calibrate the speed of their induction motors (asynchronous as well as synchronous - either type can be used), as well as the obvious pulley change, there should also be a matching voltage change included.

However, since the motors are well over-rated for this application in order to minimise speed variations, in the case of asynchronous motors particularly, as well as to minimise slip in belt drives, such a luxury feature may be omitted in the interests of 'economy of manufacture', acceptable where the motor is designed to cope with a 50Hz supply frequency and 240 volt supply which will allow it to run faster on a 220 to 240v 60Hz supply but will obviously still require a 120 to 240 volt step up transformer if designed for both 120v and 240v regions.

You only have to look at which countries compete in the World Series.

This was a long time ago - late 90s. She and her family have been back in the UK since about 2000. But thanks for the offer.

They beat us to it by about 10 years, then.

My boss brought a clock radio from US to UK (in the days they weren't available over here) and bought an auto-transformer to work it on our supply. I didn't bother to warn him that if would run rather slow.