Calculation example

Given:

Peak braking power: 13 kW

Average braking power: 6 kW

Braking time: 7 s

Cycle duration: 28 s

Minimum permissible braking resistance value of the inverter: 47 ohm, see chapter Technical data of basic device.

Required:

BW.. braking resistor

Calculation:

1) Determine the cyclic duration factor

Cyclic duration factor cdf = braking time/cycle duration

Cyclic duration factor cdf = (7 s/28 s) × 100% = 25%

When selecting the braking resistor, observe the assignment of inverter and braking resistor, see chapter Technical data and assignment to an inverter.

2) Determine the overload capacity

Determine the overload factor, e.g. for a wire resistor at a cyclic duration factor cdf of 25% from the respective diagram.

Overload factor k = 3.2

3) Calculate the braking power at 100% cdf

Braking power 100% cdf = average braking power/overload factor

Braking power 100% cdf = 6 kW/3.2 = 1.88 kW

The braking power of the braking resistor at 100% cdf must be ≥ 1.88 kW.

4) Select the braking resistor

Selected braking resistor: BW247-T.

Resistance value R_BR = 47 Ω

Peak braking power: 14.3 kW, see chapter Technical data and assignment to an inverter.

Current-carrying capacity at 100% cdf: 2 kW