External Braking Resistor

Description

An external braking resistor is required for applications in which the motor must be decelerated quickly and the internal braking resistor cannot absorb the excess braking energy.

The temperature of the braking resistor may exceed 250 °C (482 °F) during operation.

WARNING
	HOT SURFACES Ensure that it is not possible to make any contact with a hot braking resistor. Do not allow flammable or heat-sensitive parts in the immediate vicinity of the braking resistor. Verify that the heat dissipation is sufficient by performing a test run under maximum load conditions. Failure to follow these instructions can result in death, serious injury, or equipment damage.

Monitoring

The drive monitors the power of the braking resistor. The load on the braking resistor can be read out.

The output for the external braking resistor is short-circuit protected. The drive does not monitor for ground faults of the braking resistor.

Selection of the External Braking Resistor

The rating of an external braking resistor depends on the required peak power and continuous power.

The resistance R is derived from the required peak power and the DC bus voltage.

R = Resistance in Ω

U = Switching threshold for braking resistor V

P_max = Required peak power in W

If two or more braking resistors are connected to one drive, note the following criteria:

The total resistance of the connected braking resistors must comply with the approved resistance.
The braking resistors can be connected in parallel or in series. Only connect braking resistors with identical resistance in parallel in order to evenly distribute the load to the braking resistors.
The total continuous power of the connected braking resistors must be greater than or equal to the required continuous power.

Use only resistors that are specified as braking resistors. For suitable braking resistors, see Accessories and Spare Parts.

Mounting and Commissioning of an External Braking Resistor

A parameter is used to switch between the internal braking resistor and an external braking resistor.

The external braking resistors listed in the Accessories and Spare Parts section are shipped with an information sheet that provides details on their installation.