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Converting a 120 Volt Motor to 240 Volts

How to Convert the Electrical Circuit Voltage for a Motor: There are multiple problems here. You and the electrician did not discuss exactly what the 240 volt outlet would be used for. This is a big mistake, and I’m amazed that the electrician did not ask you what the circuit would be used for.

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Converting the Electrical Voltage of a Motor
Electrical Question: I have an old Craftsman table saw that can run on either 120v or 240v with a minor change within the motor, which has three input wires – a ground and two lines.  For some years, I’ve operated it at 120v, but it lacks the power to rip certain hardwoods.

Clearly, I’m missing something, but what?
Background: Michael, a Handyman from Sherwood, Oregon.

Dave’s Reply:
Thanks for your electrical wiring question Michael.

How to Convert the Electrical Circuit Voltage for a Motor

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FAQs Frequently Asked Questions and Comments

5 Responses to “Converting a 120 Volt Motor to 240 Volts”
  1. Matt says:

    Don, there are two problems here. One with the frequency difference and another with the voltage difference. Lets start with frequency: It is unlikely that you can convert the motor from 60 Hz to 50 Hz unless the motor nameplate specifies that it was already constructed to handle this frequency range. The 50 Hz European utility frequency is actually less efficient than the 60 Hz American utility frequency. This means that motors built for European systems must generally contain thicker gauge windings than an equivalent American motor in order to attain the same level of thermal performance. In other words, if your motor was built for the American 60 Hz standard, it likely has thinner motor windings, which could overheat if used on 50 Hz power. Now for the voltage problem: There are a lot of countries in Europe and they sometimes differ but in general they run on 230V per leg, where as America runs on 120V per leg and 240V when 2 alternating legs are used in combination. In a conversion from an American 120V to an American 240V system, you replace the neutral with a 2nd hot leg. In a conversion from an American 120V to a European 230V system, you still have just 1 hot leg, –but it would just carry more voltage, which the motor wires may not be rated to handle. Performing this conversion is ill advised.

  2. Dave Rongey says:

    Hi John,
    Typically the voltage of these types of motors cannot be changed unless it is specifically stated on the label. However you may want to contact the manufacturer and see if they recommend a voltage converter that may be used to change the voltage from 240 to 120.
    I hope this helps you,

  3. John Healey says:

    I bought 2 ALECO DRYWALL SANDERS from a source online. They both have 120 volt electric motors. Can these motors be changed to 240 volts as I live in New Zealand where our country is 240 volts. I look forward to hearing from you.
    Kind Regards,

  4. admin says:

    Hi Don
    It would be very helpful for you to provide the Brand, Model, and the nameplate information from this electric motor in order to see what different wiring configuration are allowed.

  5. don Julien says:

    Ask the Electrician:

    I have a 700 hp 900 rpm 4999 volt electric motor (3).
    It is 120 v 60HZ.
    I would like to change it to 220 Volts 50HZ?
    Is it possible to begin with?
    Is it fairly simple(less expensive)?
    Is it very time consuming(More expensive)?
    How does one do it?

    Much Appreciated

    don julien