Braking resistors find new applications

Although the most common use for braking resistors is in motor drives, the devices are ideally suited to other industrial applications.

Design engineers across a wide spectrum of market sectors are benefiting from the diversity, flexibility and versatility of braking resistors from TT electronics Welwyn Components.

Welwyn's range of thick-film planar braking resistors on steel offer the ability to withstand high pulses and provide a compact footprint and a low profile.

They can be easily and economically adapted to demanding applications, particularly in industrial and defence markets.

The resistors 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.

Although the most common use for braking resistors is in motor drives, the resistors have proved to be ideally 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, both civil and military.

The ongoing demand for the resistors, and proof of their versatility, demonstrates Welwyn's 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.

Thanks to their planar designs, Welwyn's 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.

Welwyn 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.

John Graham, Marketing and Sales Director, Welwyn Components, comments: "Once again Welwyn has demonstrated its knowledge, expertise and competitive edge by developing a product for a particular application but which due to its diversity and flexibility can be customised to provide niche solutions across a wide range of industries".

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