I saw on the nameplate of an induction motor that it contains two sets of voltage and current ratings. I'm wondering why that's the case. Any explanation of it would be very helpful as I am hard-pressed to find it on google. Thanks.
Were they off by a factor of two, or a factor of sqrt(3)?
Many motors for industrial use can be wired for one of two different voltages on installation -- the most common that I know of is to equip each pole with two windings that you can connect in either series or parallel for, e.g., 220V or 440V service.
It's also possible (but I don't know how common) to set up a motor to be connected in either 'Y' or delta configuration, which would give you a sqrt(3) difference.
-- Tim Wescott Wescott Design Services
Was it something like 230/460 Volts and 122/61 Amps? That would be a dual-voltage motor.
If different, how about being a bit more specific? For instance, give us the motor manufacturer and model number or at least how the data is displayed.
I can't imagine what you tried searching for that yielded no information, but try induction+motor+nameplate. Lots of hits which explain nameplate data.
It simply has double windings that can be wired in series for one voltage and in parallel for half the voltage. For example, 240 vs. 120 Volts. For half the voltage, the current would double.
The winding connections can be found in the connection box on the motor or at one end of the motor depending on size. The leads are ether numbered or color coded and there should be a connection diagram, probably on the connection box cover plate or the motor name plate that shows how to connect for the two voltages.
So you can use it on either or voltage settings.. It'll show you the wiring diagram you need to perform to set it. Low/high usually a 230/460 or near that ball park.. the higher voltages take half the current than that of the lower voltage. Normally, this is found in AC 3 phase motors and maybe a DC shunt motor with 2 voltage fields.
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