Custom Resistor Assemblies

As a safety requirement, medium voltage motor drive systems are typically discharged with dedicated resistors. This assembly can be sized based on DC bus capacitance and specified motor drive shutdown time. In addition, the current capability of the shutdown relay and safe discharge are critical to the assembly design.

Being able to accommodate high energy dissipation without risking a voltage spike across terminations is essential. The unique geometry of our 510AS slab resistor assembly allows for close spacing without compromising cooling. A compact solution is possible for 125 KJoule pulses, or greater, every 60 seconds.

Problems can occur with large motor drive and power converter systems when the drive must handle the deceleration rate of the motor. Or when speeds exceed the synchronous speeds set by the output frequency of the drive. Both conditions create regenerated power which flows back into the drive and can cause DC Bus voltage to rise. To avoid shutdown due to over-voltage, this power can be dissipated into a braking (or chopper) washer resistor assembly. Crowbar washer resistor assemblies are also used to absorb very large energy pulses for emergency shutdown of wind turbine and transport power.

While standard slab resistors work well from an electrical standpoint, sometimes a more robust thermal and mechanical solution is needed. This assembly eliminates the risk of shock or vibration induced disconnections and contaminants altogether. A machined aluminum shell houses multiple slab or axial resistors either in series or in parallel. After encapsulation, the assembly is mounted on a liquid cooled heatsink which permits continuous power through the unit.

When studying particle physics in a contained environment, a great deal of energy must be efficiently controlled. Our slab assembly was submerged in oil to provide a safe way to dissipate the heat generated when powering the linear accelerators.

Parallel tubular resistor assemblies provided an effective solution to replace a failed wire-wound resistor in an electrostatic precipitator application. The system can see a peak voltage of over 300kV and dissipate over 2 kW of power.