Application In Industrial Oven Manufacture

A Sydney based client approached us as they needed assistance in finding a suitable solution for an oven fan speed control application. The client manufactures a range of industrial ovens used for a variety of purposes from paint curing to baking enamel finishes onto metallic machined components. The ovens are constructed and designed using a motorised conveyer belt system that feeds the required items into a heating chamber which is heated by way of a number of high power industrial heating elements. When the items exit through the oven they then need to be slowly cooled in an appropriately designed ‘cooling chamber’ that had a number of industrial fans installed into the unit. To maintain the correct cooling temperature profile within the cooling chamber it is important that the speed of the fans can be controlled accurately and consistently to ensure the correct process is applied to the items passing through the chamber.

Power Resistor Tappings Used To Control Fan Speed

The fans needed to be run at different speeds by way of dropping the applied voltage supplied to the fans. By measuring the current and voltage applied to the cooling fans at different operating speeds it was determined what resistance was required for different fan speeds and what the necessary wattage for that resistance would need to be. By selecting a 100 watt HA power resistor with a resistance of 120 ohms manufactured with a tapping of 39 ohms the fan could be controlled to 3 different speed settings by using the total resistance (120 ohms), the 39 ohm tapped resistance and the 81 ohms from the tap to the other end of the resistance. These resistor values allowed for the correct voltages to be applied to the cooling fans so that the range of temperatures in the cooling chamber would be correct for the cooling process.

Specifications Of The HA Power Resistor

The 100 watt rated HA resistor is an industry standard choice for 100 watt power resistors in Australia. It has a ceramic former length of 165 mm and external diameter of 29 mm and approximate diameter of 33 mm when coated. It is available in a resistance range from 0.5 ohms to 200K ohms, This resistor is available in an adjustable version (version HAA, where the A indicates the adjustable resistance band option). The adjustable resistance range is available from 5 ohms to 37K ohms. Full data on the HA series power resistor here.