Go to FRIZLEN power resistors >>

With FRIZLEN you always stay on the move!

Dynamics with braking resistance

Not only the leading manufacturer of brake resistors, FRIZLEN is also your competent and reliable partner.

As an owner-managed family company, FRIZLEN supports anyone who is on the market for suitable brake resistors from small machine tool manufacturers to large corporations – support that ranges from advice and development to planning and production and delivery.

This site provides interesting information on the topic of brake resistors.

Why brake resistors?

What does a brake resistor do?

Brake resistors are found anywhere where something needs to be moved and braked under control – be it in elevators, cranes, high bay warehouses – or even in modern fitness equipment. But which resistor is right for your application? If it's too small, it could set fire to the surrounding area; if it's too big, it can burn a hole in your budget. The experts at FRIZLEN show you where excess electrical energy can be converted into heat – while a cool head is kept at all times.

What considerations need to be made?

If an electric motor is running in dynamic mode, it becomes a generator. Depending on the application, dynamic mode can make a huge difference to the load cycle: for example when a cable car is moving downwards, when a load is being lowered by a construction crane or in an elevator that is descending and loaded with occupants. In these cases, the motor does not consume electrical power that it normally converts into rotational energy - rather it converts rotational energy into electrical power.

If the electric motor is controlled by a frequency converter (in terms of speed), the dynamic mode increases the intermediate circuit voltage. If this voltage exceeds a certain value, the energy must be dissipated with the aid of a brake resistor. Even though there is a small brake resistor installed in most frequency converters, many applications require an additional external brake resistor because the dynamic energy of the application would overload the one that is already integrated.

How are brake resistors configured?

Among the main parameters of a brake resistor are electrical output, the resistance value and the characteristics of the load cycle.

Bremswiderstand berechnen Elektrische Leistung

Electrical Output

Bremswiderstand berechnen Widerstandswert

Resistance value

The resistance value is prescribed by the frequency converter and determines how quickly or slowly the braking energy is converted into heat – and in this way also how quickly or slowly the drive can be braked.

The resistance value recommended by FRIZLEN is above the minimum resistance value owing to the production tolerance and temperature coefficient: We allow a safety buffer of about 20 percent
(R = 1.2 × Rmin). As a result, any damage to the power electronics of the frequency converter caused by high currents is ruled out.

Load cycle

For configuration of the brake resistor, the characteristics of the load cycle (activation duration/braking time and also cycle duration) are significant.

If it is a one-off braking operation rather a cyclical one, the resistance can be set precisely to the energy generated during the braking time – provided the brake resistor has time to cool down sufficiently. As such, the brake resistor can be configured to be even smaller than with a cyclical short-term braking application.

Example: A machine needs to be completely stopped within a few seconds upon actuation of the emergency off switch.

What are protection classes and which of them might one encounter with brake resistors?

Brake resistors are used in countless locations and a diverse range of applications. This means that they have to be protected individually against contact, foreign bodies and/or the ingress of water.

FRIZLEN has a range of resistors in the following protection classes:

What do the IP codes mean?

Figure 1: Protection against contact and foreign bodies

No particular protection
Protection against the ingress of solid foreign bodies with a diameter >= 50 mm
Protection against the ingress of solid foreign bodies with a diameter >= 12.5 mm
Protection against the ingress of solid foreign bodies with a diameter >= 2.5 mm
Protection against the ingress of solid foreign bodies with a diameter >= 1 mm
Protection against dust deposits (dust protection). Complete contact protection.
Protection against the ingress of dust (dust-proof). Complete contact protection.

Figure 2: Water protection

No particular protection
Protection against vertically dripping water
Protection against vertically dripping water, operating fluids up to 15° at an angle
Protection against spray water (rain) up to an angle of 60° from the vertical
Protection against spray water from all directions
Protection against jet water (nozzle) from all directions
Protection against power jet water or severe seawater from all directions
Protection against water with submersion of operating fluid under pressurised, timed conditions

Which models are there?

Fixed resistors

Adjustable resistors

Exposed version

Flat resistors

Encapsulated resistors

Resistor units with fans (forced air ventilation)

Water-cooled resistors

Master the heat with FRIZLEN.

How hot do brake resistors get?

Brake resistors convert electrical power into heat. In doing so, the heat usually dissipates into the surrounding air – with the result that not only the brake resistor along with its housing are heated up but also the environment. FRIZLEN designs resistors in such a way that the temperature increases by approx. 200 K on the housing surface and by approx. 300 K on the resistor element.

In other words: At an ambient temperature of 20°C, the surface temperature on the housing is approx. 220°C, whereas on the resistor element it is approx. 320°C.

Bremswiderstände vor Überhitzung schützen

Why is it necessary to protect brake resistors from overheating?

Brake resistors have to withstand short periods of high braking energies and subsequent heat build-up. If the resistor is overloaded because, for example, its dimensions are inadequate, it will heat up to a very high degree. This can lead to overheating that will damage or ruin the resistor or even set alight to surrounding components. Overloads should therefore be recognised in good time and permanently prevented.

FRIZLEN offers the right solution here for different applications.