Induction Motor Starting Method

· Apply reduced Voltage at start Û Reduced Tstart

· Once speed picks up, apply full voltage

1. WYE DELTA Starter

Start in < START > & run in D

2. Auto Transformer

3. Solid state Voltage Controller for Reduced Voltage Starting

Starting Currents

Pin = Ö3 VL.IL Cosq

74.6 * 10³ = Ö3 * 440 * IL * 0.9

IL = 109A @ Cosq = 0.9 (Full Load)

Istart = 655 A, which is 6 times larger than the Full Load value. Over current relays have to be adjusted to reduce “starter” tripping of CB

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t

i / t characteristics