SIMOREG Converter Commutation Protector

General description

DC drives have been proven in daily use for many years already.
They reliably fulfill their tasks in many sectors - and are economical and require little maintenance at the same time.And yet another reason to hold on to this technology:
the SIMOREG® CCP (Converter Commutation Protector). This protects your SIMOREG DC-MASTER from the effects of a commutation failure. The result: a significantly higher plant availability. And another reason good enough to continue to rely on DC drives in the future.


For line-commutated inverters, an appropriate line-side counter voltage is required in order to commutate the current between the individual power semiconductors. Commutation can be prevented from being completed (commutation fault) as a result of uncontrolled switching operations, line supply dips (weak line supplies, thunderstorms, etc.). As a result, in the regenerative feedback direction, a high current flows through the line supply or a cross-current in the converter. This can result in fuses blowing or under certain circumstances can destroy the semiconductors.The software of the DC converter identifies if inverter commutation faults are pending and then issues the command to turn off the power semiconductors in the converter to the SIMOREG CCP.
SIMOREG CCP then turns off the power semiconductors, ensures that the conditions to reduce the current in the motor are present and absorbs the magnetic energy stored in the motor as electric energy.
The line supply voltage, the line current and the armature voltage are continually detected in the DC converter.A possible commutation fault (inverter commutation fault) is detected from these quantities, which results in the following measures being initiated:

  1. The firing pulses are immediately disabled in the DC converter

  2. The converter sends a “turn-off command” to the SIMOREG CCP (via the serial interface).

  3. The SIMOREG CCP turns-off the thyristors by switching the pre-charged turn-off capacitors in an anti-parallel configuration across all of the thyristors. The current then commutates from the converter into the SIMOREG CCP. The turn-off capacitors are initially discharged by the current that they conduct and then charged with the opposite polarity. As soon as the voltage of the turn-off capacitors has reached the value of the motor EMF, the armature current starts to decrease. However, the armature voltage continues to increase. As soon as it has reached the limit value, the resistors are switched in, which accept the energy regenerated by the motor during the remaining current reduction time.

  4. A fault message is initiated in the DC converter.

  5. SIMOREG CCP again recharges the turn-off capacitors so that a new turn-off operation is possible.

Technical data overview

Brief overview

Rated voltage


(+15 % /-20 %)

(+10 % /-20 %)

Rated current







Live area that can be covered


up to 6000

up to 1200

up to 2000

up to 1000

up to 2000

Rated supply voltage electronics
power supply


2 AC 380 (-20 %) ... 60 (+15 %); In = 1 A or
1 AC 190 (-20 %) ... 230 (+15 %); In = 2 A

Rated frequency


45 ... 65


  • Static protection against the effects of inverter commutation faults.

  • Compact

  • Practically no-loss operation

  • Maintenance-free

Customer benefits

SIMOREG CCP limits the current that flows when inverter commutation faults occur to a non-hazardous value so that the thyristors and the associated super-fast fuses are protected.This eliminates the complex and time consuming replacement of fuses after inverter commutation faults.Although inverter commutation faults cannot be prevented, their effects can be.

  • Gear units and the driven machine are protected by interrupting the current in time before it reaches its possible maximum value in the case of a fault - therefore protecting them against inadmissibly high torque surges.For high rated system currents, high-speed DC circuit-breakers were used up until now to protect the fuses against rupture.

  • By using the CCP, cost-effective protection is now possible even for lower line currents, whereby SIMOREG CCP has the following advantages when compared to high-speed DC circuit-breakers even at high current levels:
    - Protection also for circulating currents
    - Lower system costs
    - Lower space requirements
    - No additional air reactor to reduce the current rate-of-rise when a fault occurs
    - Lower operating costs, as it requires no maintenance
    - High degree of availability

Typical applications

All DC drives with regenerative feedback which are subjected to the highest demands regarding availability.