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I was going to buy a sewing machine from someone. It's rated 120v - 60 Hz (as written in the label), but the power system here is 220v - 50 Hz. Can I operate this machine with that power if I use step down transformer or stabilizer (220v to 110v) without changing 50 hz to 60 hz?

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It also depends on the complexity of the sewing machine. Is it a fancy new computerized one? Then probably not. If it's an older model that doesn't have any fancy electronics, then there's a possibility it will work. –  Doresoom May 30 at 13:17

3 Answers 3

General rule of thumb is that transformers must be run at the proper frequency they were designed for. Professor CP Steinmetz worked out why AC transformers burned up and enabled Westinghouse and the world to enjoy the use of Teslas work on AC motors and power transmission because he determined that the alloy used in transformers and motor electromagnetic circuits was very critical in controlling hysteresis (the resistance to iron changing magnetic polarity) so they wouldn't overheat.

Motors are just another form of transformer so any inductive type motors must also be run at the proper frequency to prevent overheating and run at the proper speed.

That being said, in a sewing machine, you usually have a special case as it typically is powered by a brushed universal motor which is a whole lot less sensitive to the frequency issue due to the design. Its speed is dependent on voltage and current allowed through the device and the magnetic path alloys are specifically designed for this.

So to sum it up, don't run your refrigerator on the wrong frequency (uses an inductive motor), you probably can run your sewing machine on the lower frequency (uses universal brushed motor). You will need a 50Hz transformer to step the voltage down!

The heating affects from magnetic path hysteresis are worse when running 60Hz equipment on 50Hz.

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You need a 220V, 50Hz to 110V, 60Hz converter (or transformer as some stores would call them).

Make sure you pick up one that's rated for a "heater", as it generally provides you with more than 100W power.

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A transformer will only change the voltage. It won't alter the frequency, ie it will step the voltage down to 110V, but it will still be at 50Hz. –  John May 30 at 12:29
    
@DanD., thanks! I've edited my answer. Who knew a minor typo would completely change the intent of an answer? :) –  alt May 30 at 14:47

It might run slower, as the rotational speed of most AC motors depends on the frequency of the power supply.

I'd be tempted to connect it up (through the transformer) and give it a try.

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The rotational speed of an AC motor is determined by the power frequency, if it is a fixed-speed induction motor. Sewing machines do not use fixed-speed inductions motors. For most of the last 50 or more years, sewing machines have been using brushed universal motors, which allow you to vary the speed by varying the voltage (that's what happens in the foot pedal speed control). Not sure what kind of motor is used in recent electronically-controlled sewing machines; could be a universal motor or a PWM-controlled DC motor, but it still won't be a fixed-speed AC induction motor. –  Grunthos May 30 at 15:39

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