Delta VFD-B User Manual page 190

8. Definition for Brake Usage ED%
Explanation: The definition of the barking usage ED(%) is for assurance of enough time for the
brake unit and brake resistor to dissipate away heat generated by braking. When the brake
resistor heats up, the resistance would increase with temperature, and brake torque would
decrease accordingly. Suggest cycle time is one minute
9. For safety reasons, install a thermal overload relay between brake unit and brake resistor.
Together with the magnetic contactor (MC) in the mains supply circuit to the drive it offers
protection in case of any malfunctioning. The purpose of installing the thermal overload relay is
to protect the brake resistor against damage due to frequent brake or in case the brake unit is
continuously on due to unusual high input voltage. Under these circumstances the thermal
overload relay switches off the power to the drive. Never let the thermal overload relay switch
off only the brake resistor as this will cause serious damage to the AC Motor Drive.
NFB
R/L1
S/L2
T/L3
O.L.
MC
Thermal
Overload
SA
Relay or
Surge
temperature
Absorber
switch
Note1: When using the AC drive with DC reactor, please refer to wiring diagram in the AC drive
user manual for the wiring of terminal +(P) of Brake unit.
Note2: Do NOT wire terminal -(N) to the neutral point of power system.
Revision July 2008, BE16, SW V4.08 & V5.00
100%
Brake Time
Cycle Time
MC
R/L1
S/L2
T/L3
VFD Series
Appendix B Accessories|VFD-B Series
T1
ED% = T1/T0x100(%)
T0
U/T1
V/T2
W/T3
MOTOR
+ P ( )
+ P ( )
- N ( )
- N ( )
Brake
Unit
IM
Thermal Overload
Relay
B1
O.L.
BR
B2
Brake
Resistor
Temperature
Switch
B-3