User Manual of EM730/EM730E Series Inverter
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Chapter 10
Select accessories
10.1
Braking Resistor
If the speed of the controlled motor drops too fast or the motor load shakes too fast during
the inverter operation, its electromotive force will charge the internal capacitor reversely via the
inverter, resulting in the voltage boost at two ends of the power module. This is likely to cause
damage to the inverter. The internal control of the inverter will suppress this based on the load.
If the braking performance does not meet the customer requirements, an external braking
resistor is needed to release energy in a timely manner. Due to the external braking resistor of
energy consumption braking type, the energy will be completely dissipated to the power braking
resistor. Hence, the power and resistance of the braking resistor must be selected reasonably and
effectively.
The power of the braking resistor can be calculated by the following formula:
Resistor power Pb = inverter power P × braking frequency D
D - Braking frequency. This is an estimated value, depending on the load conditions. Under
normal circumstances, D is as follows:
D=10% under ordinary loads
D=5% for occasional braking loads
D = 10% to 15% for elevators
D = 5% to 20% for centrifuges
D = 10% to 20% for oilfield kowtow machines
D = 50% to 60% for unwinding and winding. It should be calculated based on the system
design indicators.
