RCID

Brake Resistor Test Rig

Problem

Welwyn Components produce a range of power resistors for a variety of applications. One such application is in the use of power resistors for motor braking applications. As part of the development process Welwyn Components produced a new range of braking resistors which required testing to generate suitable data sheets and application notes for their customers. The RCID assisted with the design and construction of a suitable brake resistor test rig.

Solution

The test set-up consisted of a transformer, a three phase Variac supplying a bridge rectifier with smoothing capacitors to provide the necessary dc bus voltage.  A PIC microcontroller circuit is used to provide the timing and buffering of control signals via a gate drive circuit to an IGBT (Insulated Gate Bipolar Transistor) device for switching the dc bus voltage to the load braking resistor.  The low voltage PIC control (5V) switches dc bus voltages ranging from 50-900V (0.5kW – 8kW) depending on the resistor size under test. Temperature measurements were recorded using a thermal imaging camera and software.

The brake resistor tests carried out by the RCID provided information relating to the maximum pulse overload rating, maximum continuous rating and switched load rating.