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,

Vd=323.1 volts

E=346.0 volts

Id=761.1 amps

X=0.0048 ohms

Therefore,

323. 1 =

3

√

6 × 346

π

cosα−

3 × 0. 0048 × 761. 1

π

= 810 .285 cosα− 3. 4886

cosα=

326. 59

810. 29

= 0. 4033

α=66.215 degrees

From (15.2)

323. 1 =

3

√

6 × 346

2 π

( 0. 4033 +cos( 66. 215 +u))

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