Page 422 - Handbook of Electrical Engineering

HARMONIC VOLTAGES AND CURRENTS 411

The motor running details are,

Running output power 217.8 kW
Running voltage 323.3 volts
Running current 761.1 amps
Running speed 400 rev/min
Running torque 5200 nm
Running input power 246.1 kW
The transformer that feeds the bridge has the following ratings,

Rated kVA 6000
Voltage ratio, volts/volts 11,000/600
Leakage reactance in per-unit 0.04
Leakage reactance at 346 volts/phase 0.0024 ohms
Commutating reactance = 2 × 0.0024 = 0.0048 ohms.
For (15.1) the variables and parameters are,

V d = 323.1 volts

E = 346.0 volts
I d = 761.1 amps
X = 0.0048 ohms

Therefore,
√
3 6 × 346 3 × 0.0048 × 761.1
323.1 = cos α −
π π
= 810.285 cos α − 3.4886
326.59
cos α = = 0.4033
810.29
α = 66.215 degrees

From (15.2)
√
3 6 × 346
323.1 = (0.4033 + cos(66.215 + u))
2π
0.7975 = 0.4033 + cos(66.215 + u)
u = 66.215 − 65.677 = 0.538 degrees
= 0.00939 radians

From (15.4)
a 1 = cos 66.215 + cos 66.753

= 0.4033 + 0.3947 = 0.7980