Munich, Germany - The braking resistors from Welwyn are generally used for dumping energy from a motor when the speed is significantly slowed down. In this instance, the motor behaves as a generator which then returns the energy to the circuit where it is dissipated as heat in the braking resistor. An example of this application is found in a lift, where the smooth deceleration to a complete stop is achieved by braking the motor and this braking energy is subsequently lost as heat in the resistor.
Various versions of braking resistors
But whilst the most common use for braking resistors is in motor drives, the resistors have proved to be suited to other industrial applications including stairlifts, battery equipment, industrial welding, wind turbines and power generators. Welwyn is also experiencing increased interest for the resistors from engineers in the avionics market. The ongoing demand for the resistors, and proof of their versatility, demonstrates the companies ongoing commitment in responding to market needs with innovative precision components which can be readily adapted across a wide range of market sectors to achieve customised niche applications.
The design of a braking resistor must consider peak power, average power, maximum applied voltage, ohmic value, duty cycle, temperature range and heat transfer conditions. The resistor should also be intrinsically safe and flameproof. Due to their planar designs, the companys braking resistors have a low inductance figure, typically 3-6mH. In an AC machine drive, the mains fed AC is rectified to DC then inverted by electronic switching to variable frequency AC. The brake resistor is connected in series with the electronic switch across the DC voltage source.
The companys thick film steel offers excellent thermal transfer which allows high power densities for surge handling as well as continuous operation. Thermal shock and vibration testing has shown this thick film technology to be superior to other resistor technologies. The stainless steel substrate is resilient to vibration testing where typical ceramic substrates are brittle and fail.