NORDAC SK 5xxE Manual
20
Subject to technical alterations
BU 0500 GB
2.5 Brake resistor (BR)
During dynamic braking (frequency reduction) of a three phase motor, electrical energy is returned to the
frequency inverter. In order to avoid an overvoltage switch-off of the frequency inverter, an external brake
resistor can be used. With this, the integrated brake chopper (electronic switch) pulses the intermediate circuit
voltage (switching wave approx. 420V/720V DC, according to the mains voltage) to the brake resistor. Here
the excess energy is converted into heat.
CAUTION
The braking resistance and all other metal components can heat up to temperatures
above 70°C.
When mounting, sufficient distance from neighbouring components must be
maintained. When working on the components, allow sufficient cooling time beforehand
For inverter powers up to 2.2kW a standard bottom-mounted resistor (SK BR4-…IP40) can be used. This can
additionally be equipped with an optional temperature switch (bi-metal, switching point 180°C), in order to
indicate an overload. The fixing material in the side groove is enclosed. The resistor and the temperature
switch are connected by means of flexible stranded conductors. Approval: UL, cUL
Note:
Brake resistors cannot be directly mounted below –CP (ColdPlate) devices.
SK BR4-... Size
SK BR4-... Size
Chassis resistors (SK BR2-…, IP00) are available for frequency inverters from 3kW to 7.5kW. These must be
mounted in the control cabinet, close to the frequency inverter. There is a temperature switch on the braking
resistor to provide protection against overload. Connection of the resistor and the temperature switch is by
means of screw terminals. Approval: UL, cUL
SK BR2-... Size
SK BR2-... Size
