Resistance Chopper Starter in a control room

For any application using Wound Rotor Induction Motor (WRIM), there may be a requirement to further improve the starting behaviour of a motor as compared to starting with a Liquid Rheostat. In this cases, a Resistance Chopper Starter (RCS) will provide the additional performance.

The RCS can be programmed with a customised accelerating torque to provide a smooth start with a current ramp. There are two main benefits:

1. Extra protection to the mechanical parts of the drive train (electrical motor, pinions, gearboxes, etc.) and ​

2. Provides a gradual increase of current for a smooth start and reduces the voltage dip in the mill.


Background of our Technology Partner

Our SER drives are manufactured by ElectroDrives, who is one of our trusted technology partners.

Electrodrives is based in Madrid-Getafe, Spain and is a global market leader in Slip Energy Recovery (SER) Drives for Slip Ring Motors that are mainly used in the mining industry especially for SAG Mills. Following the acquisition of International Electronics S.A. (IES) in 2018, ED is focused to further innovate and continue developing customer-focused solutions for the mining industry.

Resistance Chopper Starter

Technical Specifications : Resistance Chopper Starters (RCS)



Typical Applications:

Motor Rated Power:

Typical Speed Ranges

(% of Synchronous Speed)

Typical Grid Voltages:

Motor Rotor Voltage:

Input Power Factor:


Starting Method:


Operating Temperature:

Cooling Method:

Switching Semiconductor:

Plant Communications:

Single Drive

Dual Starter (Master-slave with load sharing)

Constant or variable load (Mills, Crushers, Fans, Pumps)

500 kW up to 7,000 kW (per motor)

0% - 100% (Default for starting)

70% - 100% (Typical without starting)

60% - 100% (Extended range of motor synchronous speed)

3.3kV, 4.16kV, 6.0kV, 6.6kV, 11kV, 13.8kV

Up to 4,200V

0.85 (typical)

>99.3% ( For motors of 5,000kW and above)

Starting capability included (0-100% speed range) or External LRS/RCS

Bump-less bidirectional transfer to LRS/RCS

+0 .. +50 deg C

Air-cooled (No water or other fluids)

IGCTs rated 4,500V

Ethernet/IP, Modbus-TCP, Profibus, Profinet, Ethercat, Devicenet