SINAMICS DC MASTER for 12-pulse operation

For 12-pulse operation, two SINAMICS DC MASTER converters are supplied with voltages displaced by 30 degrees. This configuration reduces the harmonics. Each SINAMICS DC MASTER conducts half of the total current. One of the SINAMICS DC MASTER units is operated with closed-loop speed control, and the second with closed-loop current control. A peer-to-peer connection is used to transfer the current setpoint from the first to the second SINAMICS DC MASTER.

Smoothing reactors are required in the DC circuit for 12-pulse operation.

Calculating the smoothing reactor

• A smoothing reactor is used for each of the two partial converters. The reactor comprises a 2-value reactor; this means that the inductance of the reactor is defined for two current values.
• The reactor is thermally dimensioned according to the rms value of the DC reactor current.

Calculating the required inductance

1. Inductance of the reactor at 0.2 Г— I_dN (L_D1)

2. Inductance of the reactor for I_dmax (L_D2)

• for 50 Hz line frequency
  L_D1 = 0.296 Г— 10^-3 Г— V_di/(0.2 Г— I_dN)
  L_D2 = 0.296 Г— 10^-3 Г— V_di/(0.33 Г— I_dmax)
• for 60 Hz line frequency
  L_D1 = 0.24 Г— 10^-3 Г— V_di/(0.2 Г— I_dN)
  L_D2 = 0.24 Г— 10^-3 Г— V_di/(0.33 Г— I_dmax)

L = Inductance in H

I_dN half the rated DC current of the DC motor

I_dmax half the maximum current of the DC motor

V_di = 1.35 Г— V_N

V_N rated line supply voltage

12‑pulse operation