I would like to be able to control the speed of a synchronous motor as used in a clock. I could make a 230V variable speed inverter but it would be easier if I could directly drive the motor with a lower voltage 5V or 12V.

Could I rewind the motor coil using the same size former for the lower voltage?
I realise you can on;y guess this answer but what speed range may be achievable?

 

So If you want to use a synchronous motor for variable speed what are the frequencys?
What is the source of the power?
Why is a DC motor out of the equation?

 

So If you want to use a synchronous motor for variable speed what are the frequencys?
What is the source of the power?
Why is a DC motor out of the equation?

The original frequency is 50Hz.
Source of power may be a plug in USB adaptor but TBD,
It is fitted with the synchronous motor so to adapt it to a different motor would be a lot of work, possibly out of my skill set.

 

Source of power may be a plug in USB adaptor

Assuming that has a DC output, you are still going to have make an inverter.
Will the torque requirement be similar to the clock motor torque?

 

Assuming that has a DC output, you are still going to have make an inverter.
Will the torque requirement be similar to the clock motor torque?

If the new coil needs only 5V then it could be driven by an H-bridge.
Yes, I am hoping for the same torque.

 

I did some back of the envelope calculations. Does this seem correct?

If I wind a new coil with thicker wire on the same bobbin, say double the wire diameter this would give:
4x Wire cross-section
1/4 the number of turns
And hence 1/16 coil resistance and 1/16 coil inductance and so 1/16 coil impedance.

For the same ampere-turns this new coil would need:
4x the original current
1/4 the original voltage.

So there will be a wire diameter which would reduce the needed supply voltage from 230V to 5V, yes?

PS 4x current in 1/16 resistance means the same power dissipation.

 

Ask ChatGPT to do the sums?

 

I wouldn't know where to start, let alone the exact question to ask.

 

Upload this to ChatGPT :-
"A coil wound with magnet wire of diameter D1 and length L1 fills a coil bobbin and dissipates n Watts when powered by 240V AC. What length and diameter wire would be needed to fill that bobbin if the coil were instead powered by 5V AC and also dissipated n Watts?"

 

So youwant to rewind a synchronous clock motor to run on 11 volts AC instead of 220 volts AC? You will need for your new coils to produce the same magnetic flux . Consider that with a 20-fold reduction in turns you will need a 20 times increase in current to have the same ampturns. AND I am thinking that rewinding the motor will not be as easy as you hope.
I suggest not changing the motor, but use a step-down transformer in reverse, so that your 12 volt circuit can power the 220 volt motor. Just understand that with the 220 volts circuit you do need to be careful.