Before making your own power resistor, you will need to know first its components, its uses and ultimately, how it works.
What is a power resistor?
Power resistors are devised to hold large amounts of power. They have a power rating of at least 5 watts. Their components are made from materials with high conductivity, which makes cooling more efficient. They are often partnered with heat sinks which enable them to dissipate the high amount of power. Power resistors have different types; namely,
These resistors are built to withstand high temperatures, up to 450 ℃. They are formed by winding a metal around a ceramic, fiberglass or plastic. Metal caps and metallic leads are then attached to the end of the winding. For protection, the body of the device will be coated with a non-conductive paint, enamel or plastic.
2. Grid resistors
These resistors can withstand currents of over 500 amperes. They are large matrices of metal strips connected between two electrodes. Large sized grid resistors can be as big as a refrigerator. They are commonly used as brake resistors and load banks for railroad vehicles and load testing of generators.
3. Chip/SMD Resistors
Chip resistors are those which look like integrated circuit chips made from many different materials, such as pressed carbon, ceramics and metal foil. SMD resistors, on the other hand, are smaller in form. The resistor consists of a metal oxide film deposited onto a ceramic substrate. The thickness and length of film determine the resistance. With appropriate cooling, these resistors can dissipate no more than a few watts.
4. Water resistors
These resistors consist of tubes filled with a saline solution with an electrode at both ends. The water in the tubes provides a large heat capacity which allows a high power dissipation.
5. Liquid Rheostats
Also called as salt water rheostats, resistance in this type of variable resistor is controlled by submerging the electrodes into a saline solution. They may be raised or lowered by adjusting the electrode position inside the liquid. Although they are slightly outdated, they are still used in some diesel generators.
What are its general uses?
Generally, power resistors are used to convert large amounts of energy into heat. They can be used as engine breakers for locomotives and trams, as they offer controlled braking power without wearing the parts. Load banks are used to load-test generators, turbines, and battery UPS Systems. It can withstand and dissipate as much as 6 megawatts of power. They can also be used in power grounding of Y-connected generators and in medium-voltage AC distribution systems. With the help of these resistors, grounding fault will be much easier to locate because the possible fault locations are only of a limited number.
5-steps to making your own power resistor
After learning the basic components and uses of power resistors, you are now ready to make your own. Listed below are 5 easy steps you can use:
Get one old high wattage resistor. Destroy it and take the high resisting wire of your desired length.
Prepare some copper wires and use it as a
You will need a jointing filler to create the mass for coating. This is essential to protect the resistor wire from oxidation and to provide heat transfer from the wire to the environment.
Prepare a small piece of tin to create the mold.
Dry and see results.
Power resistors can be a complicated case but it is widely useful in today’s technology. The basic information listed above can serve as your guide into understanding more of these resistors.