Chapter 7 Peripheral Equipments
72
Refer to the following table for common braking resistors specifications.
Table 7-2 Motor power and brake resistor selection
At braking, the regenerated energy of motor is almost consumed on the braking resistor.
The braking power can be calculated according to the following formula:
U * U / R = Pb
In the formula, R is the value of selected braking resistor, U is the braking voltage at
stable braking of the system (it varies with different systems; for the 380VAC system, it
is generally taken as 700V), and Pb is the braking power. Theoretically, the power of
braking resistor is the same with the braking power, but generally 70% of it will be
used. Power required by the braking resistor can be calculated according to the
following formula:
0.7 * Pr = Pb * D
In the formula, Pr is power of the braking resistor, and D is the braking frequency
(proportion of the regeneration process in the whole working process), which can be
selected according to the following table:
Table 7-3 Reference for Braking Frequency
Application
Occasion
Elevator
Uncoiling
& Coil
Taking
Centrifuge
Accidental
Braking
Load
General
Application
Braking
Frequency
20%~30% 20~30% 50%~60% 5% 10%
7.2.3 Leakage Protector
There is direct earth safety capacitor or distributed capacitor inside the driver, the
motor and with the input & output lead wires. At the same time this series of drivers is
of low-noise type, and the higher carrier wave is used. Thus, the earth leakage current
Voltage (V)
Motor Power (kW) Resistance Value (Ω)
Resistance Power
(kW)
Three- phase
380V
4 50 1
5.5 50 1
7.5 50 1
11 40 1.5
15 40 2
18.5 30 4
22 30 4
30 20 6
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