FINAL EXAM WILL BE WEDNESDAY APRIL 29 FROM 10:00AM – 12:00PM IN THIS ROOM DISREGARD THE SATURDAY DATE ON THE FINAL EXAM MATRIX

Ideal Transformers

Example: Redraw the diagram below twice as a single electric circuit, the first time reflected to the high-voltage circuit, and the second time reflected to the low-voltage circuit.

Ideal Transformers Reflected to the high-voltage circuit:

Ideal Transformers Reflected to the low-voltage circuit:

Real Transformers Must account for: Resistance in the winding conductors Power (I 2 R) losses Leakage reactance Flux produced by one winding that does not link the other Energy to magnetize core Alignment of magnetic domains in core steel Electrical losses in core Hysteresis and eddy currents

Real Transformers

Polyphase Induction Motors

Stator circuit produces a rotating magnetic field.

Polyphase Induction Motors A voltage is induced across the rotor bars by transformer action (Faraday’s Law). This is possible because the rotor turns slightly (3%-5%) slower than the rotating stator field. The speed differential between the stator field and the rotor is the slip. NO SLIP  NO TRANSFORMER ACTION  NO TORQUE

Polyphase Induction Motors Speed-Torque Curves

Polyphase Induction Motors Speed-Torque Curves

Polyphase Induction Motors Power Flow / Losses