Film-Tech Forum ARCHIVE: Running a 60 cycle motor on 50 cycles

This is topic Running a 60 cycle motor on 50 cycles in forum Film-Yak at Film-Tech Forum ARCHIVE.

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Posted by Warren Smyth (Member # 1838) on 06-14-2010, 05:22 AM:

I am getting a vintage record changer from the US and the turntable motor will have been made for 110-115v at 60 cycles. The voltage conversion to 240 is the easy part. The speed issue will be a little more difficult as it no doubt has a type of induction motor. I thought I might adjust the size of the motor pulley or jocky pulley and the motor would run happily at a slower speed. However I have read that such motors tend to overheat when run at a lower line frequency.

Any tips are welcome if you have any ideas besides that of changing the motor entirely. I fully realise that many of you will think, "Why bother?"

Posted by Steve Guttag (Member # 268) on 06-14-2010, 06:31 AM:

Power inverter? That is, generate your own 120V/60Hz power.

Steve

Posted by David Favel (Member # 1125) on 06-16-2010, 01:37 AM:

For my platters there is a converter box attached to convert to NZ specs. Call Atlab who installed mine.
Or perhaps DSE would have 1 off the shelf.
The other option would be the unit connected to the projectors for a slow start, however you can adjujst the Hertz on them.

Posted by Cameron Glendinning (Member # 3516) on 06-17-2010, 07:06 PM:

240 to 120 converters, I bought mine at a place called Jaycar.

Posted by David Stambaugh (Member # 1102) on 06-17-2010, 10:38 PM:

This would work but it's expensive. I poked around looking for a DIY turntable power supply solution similar to the VPI but can't find anything. One page said building a suitable power supply that changes the line frequency is non-trivial.

Posted by Bruce McGee (Member # 131) on 06-18-2010, 11:01 AM:

Dont 60 cycle motors run a bit warmer on 50 cycle power?

I have an old Collaro (UK made) turntable from an old Magnavox stereo that has a 50 cycle motor on it. It runs fine, but spins the records a bit fast. I've got feelers out looking for a motor for this unit now.

Posted by Warren Smyth (Member # 1838) on 06-20-2010, 08:00 AM:

Thank you everyone for your suggestions. It is correct that getting a converter to change the frequency is not a simple matter. The professional ones are expensive and would represent over kill. Most domestic ones only change the voltage as most modern electrical goods run happily at either 50 or 60 cycles.

The motor heating issue only apparently appies when running a 60 cycle induction motor on 50 cycles, not the other way round.

I thought I might try to get an American power inverter which coverts 12v DC to 110 V AC. These are quite common and are used for running appliances in cars but naturally the US ones are not available here. I assume these produce a sine wave at 60 cycles. I could then run that from a 12v DC power supply. The motor only draws about 30 watts.

quote: Bruce McGee
I have an old Collaro (UK made) turntable from an old Magnavox stereo that has a 50 cycle motor on it.

Pity it is not from a 1937 Webster record changer Bruce, we could do a swap.

Posted by Tony Bandiera Jr (Member # 2365) on 06-20-2010, 11:20 PM:

quote: Warren Smyth
I assume these produce a sine wave at 60 cycles.

Not a safe assumption sir. Most of the inexpensive converters produce a stepped sine wave or even a square wave which will at the least make the motor run erratically or more likely burn it up.

You can find those converters that produce a "true sine wave" output, the ones that do will usually brag about it in the packaging or in the specs.

It will still be the best solution in your case, just choose carefully.