100 Watt Resistor Application And Specification

We had a recent enquiry for a power resistor that was to be used in the mining industry for a braking resistor for a conveyor belt system used in a coal loading terminal in Newcastle. The motor requiring the braking resistor was slightly unusual in that it was a d.c. (direct current) motor. The resistor required had the following requirements in its specification:

  1. 3.9 ohm resistance
  2. Maximum current rating 4.5 amps (d.c.)

Using basic resistor theory we determined that the most appropriate power rating for the resistor would be found by using the formula Power (dissipated in the resistor) = Current squared X Resistance which in this instance equals 78.9 watts. Allowing for a ‘safety margin’ it was determined that the use of a 100 watt power resistor would best suit the requirement for this application.

HA Power Resistor Specifications

The type HA power resistor is an ideal resistor for the application. It has the following specifications:

  1. 100 watt power rated resistor
  2. 165 mm ceramic former length
  3. 29 mm ceramic former outside diameter
  4. 191 mm mounting feet centres ( these resistors are supplied with horizontal mounting feet that fit into the ceramic former and allow for easy mounting of the resistor assembly)
  5. A resistance range from 0.5 ohms to 200 kohms.

This style of power resistor has been used in industry for well over 50 years and its robust construction, resistance winding coating and electrical construction make it very rugged in a diverse range of environmental conditions.

HA 100 watt power resistor image

The Ideal Resistor For Custom Applications

Because the windings are essentially ‘made to customer requirement’ the resistance values for this range of resistors are tailored to the clients circuitry needs and a high level of ‘customisation’ is available to ensure long term reliability of the resistor in the clients’ application.

In this instance the client mounted the 3.9 ohm, 100 watt resistor in the control box enclosure that was located near the conveyor operators panel which provided for sufficient ventilation and ease of access in the future should it be required. Electrical connection onto the resistor assembly was made via industry standard ‘quick connect’ terminals. The image above shows the HA 100 watt power resistor in its ‘fixed’ resistance form and its ‘adjustable resistance’ form.