. Electrical news and engineering . gramNo. 2, we should have the simplest form of polyphase generatorand motor. Instead of having two coils A, B, between the polesX, S, we might space three, or any other convenient numberproducing 2 phase, 3 phase or 4 phase E M Fs. ^ As, however, theprinciples of polyphase E M Fs apply to any number, and there isno advantage in using more than three, we shall not consider anyhigher number. In a polyphasal generator it is evident we canhave just as many complete circuits as there are phases. In a 2phase there are two sets of independent coils ; the ends of th
. Electrical news and engineering . gramNo. 2, we should have the simplest form of polyphase generatorand motor. Instead of having two coils A, B, between the polesX, S, we might space three, or any other convenient numberproducing 2 phase, 3 phase or 4 phase E M Fs. ^ As, however, theprinciples of polyphase E M Fs apply to any number, and there isno advantage in using more than three, we shall not consider anyhigher number. In a polyphasal generator it is evident we canhave just as many complete circuits as there are phases. In a 2phase there are two sets of independent coils ; the ends of thesemight therefore be brought to four contact rings, and the ends ofthe three independent sets of a 3 phase might be brought to 6contact rings, as the ends of a single phase are connected to twocontact rings. But a study of the wave diagrams of a 2 phaseand of a 3 phase circuit shew that we can greatly simplifymatters, and do with less copper. Take a more simple diagrainof two phase coils at right angles to each other. In the upper. Diagram 5. half of the E M F circle, the E M F in each coil is positive and thecurrent will flow from the outside end of the coil towards tlieinside end, in the direction of the arrows; here the E M F in eacli otthe return wires is in the same direction, therefore we can com-bine them into one, instead of having two. Suppose the coilshave revolved into the second position ; here the E M F in the 2nd £ if f k -:^ ^ ./^^ € Diagram 6. coil is positive current flowing in the same direction as E M F in the ist coil is however negative (the coil being belowthe horizontal diameter) and the EM F will have reversed ; there-fore the current in i will now flow in the opposite direction towiiat it did before—in the direction of the new arrows. But it isplain that here again, if we join the outside ends of 2 and i, thereturn current from 2 can flow down i, the E M Fs being in the samedirection. Therefore in the two phase system instead of havingt
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