Braking Resistors Calculator

Calculate Continuous & Braking Power from Known Motor Power

To calculate the right size of the resistor you need the characteristic data of the load cycle: brake time or duty cycle and the total cycle time. Furthermore you need the brake power Pbr and the minimum resistance value Rmin which is defined by the VFD.

Due to production tolerance and temperature coefficient the recommended resistance value is significantly higher than the minimum resistance value. Here we use a safety factor of 20 % (R = 1,2 x Rmin), effectively preventing possible damage to components of the VFD due to high currents.

Would you like to Calculate Continuous Power (Pcont) from a known Braking power instead?

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BRAKING RESISTOR PRODUCTS :
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KABR - METAL CLAD BRAKING RESISTORS
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KCBR – WIRE WOUND BRAKING RESISTORS
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KAHB – METAL CLAD HIGH POWER BRAKING RESISTORS
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KSAH – SLIM PROFILE AL HSD RESISTORS

Dynamic Braking Resistors from KWK:

KWK Resistors has the expertise to compute, design customized and application-specific resistors that are particularly good at handling high pulsed powers. Dynamic Braking Resistors from KWK come with varied resistance, power, and current ratings. KWK Resistors also require very little service and maintenance.

These heavy-duty braking resistors are designed to be rugged so as to withstand heavy loads and frequent start-stop cycles. Resistors come in different form factors like edge-wound and wire-wound resistors.

The role of braking resistors in VFD >>
Related Article:

The role of braking resistors in VFD >>
Things to remember -

Ppk = Peak Power Value Help is hereThe peak power is the maximum power that the power supply can sustain for a short time and is sometimes called the peak surge power.

R_min = Minimum Resistance Value

tBr = Braking (on)Time

ttl = total Cycle Time

How do you calculate the size of a dynamic braking resistor -

To specify the resistor we need to know three things: the energy per stop, the duty cycle and the ohmic value. The first two are usually combined into one variable, the power of the resistor.

  • Power

    Ideally you calculate the mechanical energy involved in each stop, using one or more of the above formulae. This will be the sum of the kinetic, rotational and potential energies, less any friction losses if these are signifcant, less the electrical losses in the motor/inverter system.

  • Ohms

    The ohmic value sets the rate at which we put the energy into the resistor – the braking power. The lower the ohmic value, the higher the power.