Polyphase Motors
Polyphase motors are either two- or three-phase motors. Their construction is similar, but the wiring of the coils is different. Two-phase motors are seldom used and will not be discussed in any detail. Suffice it to say that the phase relationship of the voltages in this type of system is 90° apart. Voltage between phases will be equal to 1.414 (square root of 2) times the single-phase voltage. This value is less than the 1.73 multiplier (square root of 3) for three-phase systems. The theory of operation for two-phase motors is the same as for three-phase motors.
General Considerations
Three-phase motors are common in industry. They vary in size from fractional horsepower to several thousand horsepower. Usually they ...
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