Right voltage, wrong frequency of operation

[fisico30]

A general appliance needs to be fed the right voltage to operate correctly.
For instance, a hairdryer in Europe works at 220 V, in the US at 110V.
What if the voltage is correct but the frequency is not?
(In Europe 50Hz, in the US 60Hz)

How does that affect the performance of the appliance? Why? Can you still use it even if the frequency is different? Say the difference is even bigger than 10 Hz, like 100Hz. Would that be a real problem?
thanks a lot

 

[f95toli]

For most devices the frequency won't matter much. The rectifier circuitry will work equally well for 60 and 50 Hz (when the same device in sold in Europe and the US the only difference is often how the transformer is connected). Many circuits would work even better if the frequency was a bit higher.
Note, however, that certain pieces of equipment use the 50/60 Hz as a "clock" although I believe that is rare nowadays.

 

[dlgoff]

AC motors derive their speed(rpm) for the source frequency. Motors will run slower with a 50Hz source than with a 60Hz source. As the frequency increases, there would be a limit in which the motor can respond.

 

[isly ilwott]

Frequency matters. The impedance of an inductive device (such as an AC motor) is dependent upon the frequency. Lower the frequency and you lower the ac impedance. Lower the impedance and you increase the current drawn by the device. Increase the current and you increase the I^2R losses. Excess heat may damage the device.

 

[fisico30]

thank you isly ilwott. I see your point. Too much current to much heat. No good.
what do you think about dlgoff response about the speed of the motors?
not all electronic devices have a motor right? for those simple ones that do (hairdriers, washers, etc...) do you believe it can be dangerous?

 

[mgb_phys]

For small device used intermittently (hairdryers, shavers, coffee grinders ) it doesn't really matter. For larger motors like washing machines/dryers I would be more concerned.

 

[russ_watters]

Large equipment like commercial air conditioning equipment is often identical in 50 and 60 hz versions - they just de-rate them for the 50 hz versions.

 

[rbj]

Note, however, that certain pieces of equipment use the 50/60 Hz as a "clock" although I believe that is rare nowadays.

i don't know why it would be more rare. certainly an electronic clock (e.g. a clock radio) can base its clock on an internal crystal oscillator, which can have very good short-term accuracy. but normally for these kinda clocks, the user wants long-term accuracy. a crystal that is off (say high) in frequency remains off (high) indefinitely and that error accumulates over time. the power grid is controlled in such a way that the integral of frequency (the count of 60 Hz cycles) remains constrained to a maximum deviation from true time (what they might get from an atomic clock). so an old mechanical clock (or an electronic one based on the power line frequency) will not drift from accurate time to inaccurate (assuming no power failure) where a crystal-based clock (like your wristwatch), if it's a little slow loses more and more time as it ticks on. a North American power-line based clock might indicate only 5 seconds elapsed in the (true) time of 6 seconds if it's plugged into European power.

 

[berkeman]

Frequency matters. The impedance of an inductive device (such as an AC motor) is dependent upon the frequency. Lower the frequency and you lower the ac impedance. Lower the impedance and you increase the current drawn by the device. Increase the current and you increase the I^2R losses. Excess heat may damage the device.

In addition, higher frequencies result in higher losses in AC Mains-style transformers. So it can definitely cause an overheating problem if you try to operate a 60 Hz transformer at, say, 400Hz. You could even start a fire by doing that. Don't ask me why I know this to be true...

 

[Pumblechook]

I am not sure what diff frequency makes to a small induction motor which is probably not synchronous... It might be synchronous when lightly loaded.

 

[free1616]

industries consuming morethan 50,000 units per day with 49 Hz frequency cause a reduction of 2000 Wh per day, when with a frequency of 50 Hz,How it is possible