Selecting the braking resistor

DANGER

The supply cables to the braking resistor carry a high DC voltage (ca. DC 900 V).
Severe or fatal injuries from electric shock.
  • The braking resistor cables must be suitable for this high DC voltage.
  • Install the braking resistor cables according to the regulations.

 

WARNING

The surfaces of the braking resistors get very hot when the braking resistors are loaded with Prated.
Risk of burns and fire.
  • Choose a suitable installation location. Braking resistors are usually mounted on top of the control cabinet.
  • Do not touch the braking resistors.

 

INFORMATION

  • The data applies to BW.., BW..-T and BW..-P braking resistors.
  • For BW.., BW..-T and BW..-P braking resistors, plan for a load derating of 4% per 10 K from an ambient temperature of 45 °C. Do not exceed a maximum ambient temperature of 80 °C (176 °F).
  • The overload factor of the BW..-T and BW..-P braking resistors is limited by using an integrated temperature relay:
    • BW..-T up to overload factor 12
    • BW..-P up to overload factor 40
  • The maximum permitted line length between MOVITRAC® B and braking resistor is 100 m (328 ft).

 

  • Parallel connection

Two braking resistors must be connected in parallel for some inverter/resistor combinations. In this case, set the trip current on the bimetallic relay to twice the value of IF provided in the table.

  • Peak braking power

The peak braking power can be lower than the load capacity of the braking resistor due to the DC link voltage and the resistance value. Formula for calculating the peak braking power:

Pmax = V2DC/R

VDC is the maximum permitted DC link voltage.

    The following table lists the peak braking power levels that are possible for the different resistance values.

    Resistance in Ω

    Peak braking power in kW

    400/500 V units

    230 V units

    100

    9.4

    –

    72

    13.0

    –

    68

    13.8

    –

    47

    20.0

    –

    39

    24.0

    –

    27

    34.8

    8.7

    18

    52.2

    –

    15

    62.7

    –

    12

    78.4

    19.6

    9 (2 × 18 Ω parallel)

    –

    26.1

    6

    156

    39.2

    Additional information