Determine firing angle alpha - the power fed back to the

Question

A 3-Φ full converter is used to control the speed of a 100hp, 600V, 1800rpm, separately excited DC motor. The converter is operated from 3-Φ, 480V, 60Hz supply. The motor parameters are R_a=0.1 ?, and L_a=0.5mH, K_Ø=0.3V/rpm. Rated armature current is 130A.

a. Rectifier Operation: The motor is running at rated conditions at 1500rpm. Assuming ripple free current,

Determine,

1.Firing angle α, and

2.Supply power factor.

b. Inverter Operation: The DC machine is operated in regenerative braking mode at 1000rpm and rated motor current.

Determine:

1. Firing angle α,

2. The power fed back to the supply, and

3. Supply power factor.