Understanding AC Motor Basics: Why a 120V Motor Can't be 3-Phase

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A 120V AC motor cannot be three-phase because standard three-phase power sources in the US start at 208V. While technically possible to have a 120V three-phase motor, it would require a non-standard 120V three-phase supply. The lowest common three-phase voltage available is 208 VAC, which is 208V line-to-line and 120V line-to-neutral. Additionally, using a Variable Frequency Drive (VFD) could allow a three-phase motor to operate at 120V, but it would run at reduced speed. Understanding these voltage standards is crucial for electricians studying electric motors.
Soleste23
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I have never seen a 120 volt three phase motor.
I have just started my electrician career and I am studying electric motors. why an 120v ac motor can not be 3 phase ? .
 
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Soleste23 said:
Summary: I have never seen a 120 volt three phase motor.

I have just started my electrician career and I am studying electric motors. why an 120v ac motor can not be 3 phase ? .
Are you aware of any 3 phase power sources that are 120 volts leg to leg?
 
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There's no physical reason that a 3-phase motor can't be 120 Volt, but it would require a 3-Phase 120 VAC supply (which is not a standard anywhere that I know of). In the US, the lowest common 3-Phase voltage is 208 VAC - that's 208 VAC L-L and 120 VAC L-N.
 
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1652988611774.png

https://www.plugsocketmuseum.nl/ThreePhaseTransformers.html
 
Something to think about: A VFD driving a three phase motor would output 120 volts at about half speed in order to keep the frequency to voltage ratio correct.
 

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