Polyphase Induction Motors

Figure 1: A typical three phase motor.

                                                     

Figure 2: Stator of a three phase motor.

Figure 3: Rotor of a three phase motor.

Figure 4: Stator of a three phase motor with all the coils in their slots.

Figure 5: A portion of a three phase winding as it would appear if the slots were laid flat.

Figure 6: Two typical types of slots found in the stators of three phase motors.

Figure 7: Motor using cuffed insulation in slots.

Figure 8: An untaped coil used in semiclosed slots.

Figure 9: Starting to place coils in slots.

Figure 10: The method of placing one side of each coil in slot.

Figure 11: The method of placing the sides of two coils in a slot with insulation.

Figure 12: A diagram of a star connection, also called a Y connection.

Figure 13: A diagram of a delta connection.

Figure 14: A 36 coil, three phase motor with coils divided into poles.

Figure 15: The true shape of coils shown in figure 14 above.

Figure 16: A simplified diagram of the coils in a three phase four pole motor.

Figure 17: Three groups in one pole, each group has three coils.

Figure 18: How the coils in a group are connected together.

Figure 19: A side view of the coil connections shown in figure 18 above.

Figure 20: Three coils are group wound. Connections between coils are automatically made during the winding process.

Figure 21: Coils connected in twelve groups of three coils each. Note that all poles are alike.

Figure 22: Connections of groups of phase A.

Figure 23: Phase C connected exactly like phase A and connected before phase B to simplify connections.

Figure 24: The current flow in the B phase is opposite to the current flow to both the A and C phases, this is shown by the arrows under each group.

Figure 25: A diagram similar to figure 24 above except that rectangles are used instead of coils.

Figure 26: A schematic diagram of a three phase four pole series star (1Y) motor.

Figure 27: A schematic diagram of a three phase four pole series delta motor.

Figure 28: The A phase connection in a four pole series delta motor.

Figure 29: The C and A phase connections in a four pole series delta motor. The end of the A phase is connected to the beginning of the C phase.

Figure 30: A complete diagram of connections for a three phase  four pole series delta motor.

Figure 31: Markings and connections for Y connected dual voltage motor.

Figure 32: Markings and connections for delta connected dual voltage motor.

Figure 33: Wye delta connected dual voltage motor.

Figure 34: Nine leads wye connected part winding motor. This is similar to a 9 leads dual voltage motor.

Figure 35: Two methods of connecting a 9 leads delta part winding motor.

Figure 36: A four pole constant torque two speed motor. The parallel star (2Y) connection is used for high speed operation, the series delta for low speed operation. T4, T5, T6 to line; T1, T2, T3 connected together, for high speed. T1, T2, T3 to line; T4, T5, T6 not connected, for low speed.

Figure 37: A two speed constant horsepower motor. The series delta connection is used for high speed operation; two parallel star for low speed. T1 T2 T3 to line; T4 T5 T6 connected together for low speed. T6 T4 T5 to line; T1 T2 T3 not connected for high speed.

Figure 38: Two speed 7 leads motor. Constant torque.