Rotor Resistor Starters

The magnitude of starting torque can be controlled by resistance values; the number of starting steps vary depending upon peak torque limitations required by application. For example, a conveyor drive would have more starting steps than a ball mill. Single starting times can be set by timers, PLC control or tacho feed back.

Rotor resistance starters are comprised of three sections:

For High Voltage wound motors, on the stator side, a High Voltage Circuit Breaker or Vacuum Contactor can be incorporated into the design. Low voltage motors use standard Contactors and motor protection units.

Rotor Contactors are selected for staged starting duty with the final slip ring shorting Contactor being fully rated to the motor full load current.

Starter housing are designed for either indoor or outdoor locations – sized to meet the environment, number of Contactors and Resistors for the application.

Resistors need to be designed to allow for the starting duty cycle without overheating or too high a change in resistance value when hot, as this influences the starting characteristics.

Rotor Resistance Starters are very reliable, need little maintenance, not unduly influenced by extreme environmental conditions and for outdoor application can be cyclone rated.

Backer Cynebar Ohmic designs and manufactures heavy-duty Rotor Resistance Starter Cubicles (RRCs) for wound rotor induction motors (WRIMs), providing reliable motor starting, reduced inrush current, improved starting torque and enhanced process control. These engineered rotor resistor starters are built for harsh mining, materials handling, bulk processing, water treatment and heavy industrial environments.

Every system is custom designed to suit individual motor characteristics, load requirements, starting duty cycles and site environmental conditions.

A rotor resistance starter introduces external resistance into the rotor circuit of a wound rotor (slip ring) motor during startup. As the motor accelerates, resistance is progressively removed through staged contactors until the rotor is fully shorted for normal running.

This method provides:

Rotor resistance starters remain one of the most effective solutions for starting large slip ring motors driving high-inertia loads.

Heavy-Duty Industrial Construction

Our rotor resistance starter cubicles are designed for continuous operation in demanding environments that may contain:

Each cubicle has separate compartments for resistor banks, contactors and control equipment. This segregation improves reliability, maintenance access and thermal management.

Resistor grids are manufactured from high-performance resistor alloys, including 316 stainless steel and iron-chromium-aluminium (FeCrAl) alloys, providing:

Rotor resistance starters generate significant heat during motor acceleration. Our designs ensure:

Resistor grids are designed to operate with maximum grid temperatures not exceeding 300°C under specified operating conditions.

Custom resistor bank configurations are available with multiple starting stages to suit:

The staged resistance arrangement enables smooth acceleration while minimising mechanical and electrical stress.

Reduced Mechanical Stress

By controlling motor acceleration, rotor resistance starters reduce shock loading on:

This helps extend equipment life and reduce maintenance costs.

Rotor resistor systems deliver high starting torque while limiting current draw, making them ideal for high-load startup applications.

Our systems are engineered to withstand repeated starting cycles while maintaining stable electrical performance and thermal integrity.

Features may include:

Mining & Resources

We can integrate a range of monitoring and protection systems, including:

These features help maximise uptime while simplifying maintenance and troubleshooting.

Backer Cynebar Ohmic is an Australian manufacturer based in Brisbane, delivering custom-engineered electrical heating and resistance solutions for industrial customers throughout Australia and overseas.