A power resistor is a passive two-terminal electrical component that resists or limits the flow of electric current in a circuit. Bridge cranes, locomotives, lift trucks, elevators, conveyors, battery lines, power supplies, industrial controls, arc and spot welders, AC variable frequency drives and DC drives, dynamic braking, harmonic filtering, current sensing, neutral grounding, load banks, and mining applications are some typical industrial applications of power resistors.
The property of resistors to dissipate heat can be used to slow down a mechanical system. This technique is called dynamic braking and such a resistor is called a dynamic braking resistor. The point of a dynamic braking resistor is to slow down or to quickly stop a motor by dissipating the excess voltage as heat. Thus, it ensures proper motor operation, allowing heavy loads to stop quickly and protects the drive from damage. The motor of a decelerating load acts as a generator, converting the kinetic energy of the load into electrical energy. The dynamic braking resistors in a dynamic braking circuit slows the load by transforming this electrical energy into heat energy.
- Speedy braking of DC and AC motors.
- Lower abrasion of friction braking components.
- Keep motor voltages within secure levels.
- No fear of a runaway due to overheated friction brakes in some motors.
- Reduce wasted time during braking.
- Increase life and service reliability
- Absorb thermal expansions and contractions.
The DC resistance of a motor armature is very low. When DC voltage is first applied, heavy current flows which will lead to the armature windings getting overheated and burnt. To avoid that, the starting current is limited by using a starting resistor. That is achieved by using a starter to start the DC motor. The idea of a DC motor starter is adding external resistance in series with the armature windings to reduce initial current. Hence, the DC motor safeguards the motor’s circuitry by lowering the starting current through the resistance. 3 point starter, 4 point starter, no-load release coil starter, thyristor controller starter etc. are several types of dc motor starters.
Starting resistors are deployed to start large asynchronous machines with slip ring rotors. The starting resistor in the rotor circuit is completely switched on first and then switched off again in phases until the full motor power is available. The starting resistor limits the starting current of the motor, thereby the motor gains momentum.
Load Resistance Units
Load resistors are connected at the output side of the circuit. A heavy load will draw more current while a light load will draw less current. A load less circuit will draw minimal current. The main purpose of applying these resistors is to increase or decrease the power at the output as per the requirements. Load resistors are used to test transformers, batteries, generators, chargers, UPS devices, inverters or emergency power generators. High load resistance is favored mostly, as it ensues maximum voltage transfer.
In a wire wound resistor, a wire with a high resistivity is wrapped around an insulating core to provide the resistance. Carbon resistors may be small and cheap, but it’s wise to use wire wound resistors instead of them.
- They can be used in higher power circuits.
- They are not that sensitive to noise.
- They are thermally stable.
Our resistors are removing harmful electrical signals and offering a stable power grid. Our power resistors are providing overvoltage protection in a variety of industrial applications in UAE.