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 × IdN (LD1)
2. Inductance of the reactor for Idmax (LD2)
- Inductance for 50 Hz line frequency
L D1 = 0.296 × 10-3 × Vdi/(0.2 × IdN)
L D2 = 0.296 × 10-3 × Vdi/(0.33 × Idmax)
- Inductance for 60 Hz line frequency
L D1 = 0.24 × 10-3 × Vdi/(0.2 × IdN)
L D2 = 0.24 × 10-3 × Vdi/(0.33 × Idmax)
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 × VN
V N rated line supply voltage