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SV800/SV800A User Manual Appendix A: Braking
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Appendix A: Braking
A.1 Selection of braking unit and braking resistor
A.1.1 Selection of braking resistor resistance
When braking, almost all of the motor regenerative energy is consumed by the braking resistor.
According to the formula:
Pb=U*U/R
U: System braking voltage (U normally is 700V AC 380V grade inverter)
Pb: Braking power
A.1.2 Selection of braking resistor power
In theory, the braking resistor has the same power as the braking power, but considering the
de-rating is 70%. According to the formula:
0.7*Pr=Pb*D
Pr: The power of the braking resistor;
D: Braking rate, which is the proportion of the regeneration process to the entire working
process.
Common
application
occasions
Elevator
Unwinding
and
Rewinding
Centrifuge
Accidental brake
load
General
occasions
Braking rate
20% ~30%
20 ~30%
50%~60%
5%
10%
Table A-1 is the guidance data. Users can choose different resistance values and power
according to the actual situation. (However, the resistance value must not be less than the
recommended value in the table, and the power can be large.) The selection of the braking
resistor needs to be based on the actual application system. The power generated by the motor is
determined by the inertia of the system, the Dec. time and the energy of the potential energy
load. The larger the system's inertia, the shorter the deceleration time and the more frequent
braking, the greater the power and the smaller the resistance of the braking resistor needed.