12.09.2019
13
QUICK START GUIDE :
brake
unit extern
7.5.
Brake resistor calculation and selection :
Resistor value indirectly decides the system control moment. Too small brake moment will lead
inverter OU.
380V Standard DC motor
：
P Motor power
K---------- Conversion efficiency of the machine energy when feedback comes. Usually 0.7 (applicable
for most occasion)
V
DC working voltage. 670V
R
Brake resistor equivalent value
Q
Brake resistor rated waste power
S
Brake resistor waste power safety coefficient 1.4
Kc--------- The proportion of regeneration in the motor working procession (evaluate according to the
load)
Normal Kc Value as below:
Centrifuge
Kc=5%
——
20%
Elevator
Kc=10%
——
15%
Oil field
油田磕头机
Kc=10%
——
20% Crane lower than 100m
Kc=20%
——
40% Occasional brake load Kc=5%
Others Kc=10%
Calculation norm
：
Motor electricity regeneration should be absorbed completely by resistor.
Motor regeneration energy=1000*P*K=resistor
absorptivity V*V/R
）
Resistor power calculation norm:
otor electricity regeneration should be absorbed completely by resistor and transfer to heat energy.
Q=P*K*Kc*S=P*0.7*Kc*1.4 Approximately Q=P*Kc
And
:
resistor power=motor power* Kc
7.6.
Brake unit safty limit
Current in brake unit is 670/R. Such current should not be larger than that the allowable maximum
current.
