Residual Current Devices (Rcd) And Insulation Resistance Monitor (Irm) - Danfoss VLT AQUA Drive FC 202 Design Manual

Electrical Installation Con... VLT® AQUA Drive FC 202
NOTICE
The resistor brake circuit resistance selected should not be higher than what is recommended by Danfoss. Enclosure
sizes E1h–E4h contain 1 brake chopper.
NOTICE
If a short circuit occurs in the brake transistor, power dissipation in the brake resistor is prevented only by using a
mains switch or contactor to disconnect the mains from the drive, or a contact in the brake circuit. Uninterrupted power
dissipation in the brake resistor can cause overheating, damage, or a fire.
WARNING
FIRE HAZARD
Brake resistors get hot while/after braking. Failure to place the brake resistor in a secure environment can result in a fire
risk and property damage.
•
Place brake resistor in a secured location away from accidental contact and flammable material.
10.7.2 Control with Brake Function
A relay/digital can be used to protect the brake resistor against overloading or overheating by generating a fault in the
drive. If the brake IGBT is overloaded or overheated, the relay/digital signal from the brake to the drive turns off the brake
IGBT. This relay/digital signal does not protect against a short circuit in the brake IGBT. Danfoss recommends a means to
disconnect the brake if a short circuit occurs in the brake IGBT.
In addition, the brake makes it possible to read out the momentary power and the average power for the latest 120 s. The
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brake can monitor the power energizing and make sure that it does not exceed the limit selected in parameter 2-12 Brake
Power Limit (kW). Parameter 2-13 Brake Power Monitoring selects what function occurs when the power transmitted to the
brake resistor exceeds the limit set in parameter 2-12 Brake Power Limit (kW).
NOTICE
Monitoring the brake power is not a safety function; a thermal switch connected to an external contactor is required for
that purpose. The brake resistor circuit is not ground leakage protected.
Overvoltage control (OVC) can be selected as an alternative brake function in parameter 2-17 Over-voltage Control. This
function is active for all units and ensures that if the DC-link voltage increases, the output frequency also increases to limit
the voltage from the DC link, which avoids a trip.
NOTICE
OVC cannot be activated when running a PM motor, while parameter 1-10 Motor Construction is set to [1] PM non-
salient SPM.

10.8 Residual Current Devices (RCD) and Insulation Resistance Monitor (IRM)

Use RCD relays, multiple protective grounding, or grounding as extra protection, provided they comply with local safety
regulations.
If a ground fault appears, a DC current can develop in the faulty current. If RCD relays are used, local regulations must be
observed. Relays must be suitable for protection of 3-phase equipment with a bridge rectifier and for a brief discharge on
power-up. See chapter 10.9 Leakage Current for more details.
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