Brake Resistor (Br); Fig. 3: Bottom-Mounted Brake Resistor Sk Br4; Fig. 4: Chassis Brake Resistor Sk Br2 - nord NORDAC PRO SK 500E Series User Manual

SK 54xE – Users Manual for Frequency Inverters

2.6 Brake resistor (BR)

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CAUTION
Danger of burns
The heat sink and all other metal components can heat up to temperatures above 70 °C.
Touching such components may cause local burns to the affected parts of the body (hands, fingers, etc.).
To prevent such injuries, allow sufficient time for cooling down before starting work - the surface temperature
should be checked with suitable measuring equipment. In addition, keep a sufficient distance from adjacent
components during installation, or install protection against contact.
During dynamic braking (frequency reduction) of a three-phase motor, electrical energy is returned to
the inverter. An external brake resistor can be used in order to prevent the FI from being shut down
due to overvoltage. With this, the integrated brake chopper (electronic switch) pulses the intermediate
circuit voltage (switching wave approx. 420 V / 775 V (/825 V) DC, according to the mains voltage)
(115 V, 230 V/400 V(/500 V)) to the brake resistor. Here the excess energy is converted into heat.
For inverter powers up to 7.5 kW (230 V: bis 4,0 kW) a standard bottom-mounted resistor (SK BR4-
..., IP54) can be used. Approval: UL, cUL
Note: Brake resistors cannot be directly mounted below ...-CP (ColdPlate) devices.
SK BR4-... Size 1 SK BR4-... Size 2

Fig. 3: Bottom-mounted brake resistor SK BR4-...

For frequency inverters above 3kW chassis-mounted resistors (SK BR2-..., IP20) are also available.
These must be mounted in the control cabinet, close to the frequency inverter. Approval: UL, cUL
SK BR2-... Size 3 SK BR2-... Size 4 and above

Fig. 4: chassis brake resistor SK BR2-...

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36 BU 0505 EN-3021