Delta Electronics VFD-S User Manual

Appendix B  Accessories|VFD-S Series 

B-2 

Revision August 2008, SE09, SW V2.61

7. 

Please read the wiring information in the user manual of the brake unit thoroughly prior to 

installation and operation. 

8. 

In applications with brake resistor or brake unit, Pr.6-00 (Over-voltage stall prevention) 

must be disabled. And Pr.8-15 (AVR function) shall not be used. 

9.

 

Definition for Brake Usage ED% 

Explanation: The definition of the barke 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 

 

100%

T0

T1

Brake Time

Cycle Time

ED% = T1/T0x100(%)

 

 

10.  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 braking 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. 

 

R/L1
S/L2

T/L3

NFB

MC

  VFD Series

MOTOR

O.L.

U/T1

V/T2

W/T3

SA

R/L1
S/L2

T/L3

MC

IM

Thermal

Overload
Relay or

temperature
switch

Surge
Absorber

B1

B2

BR

O.L.

Thermal Overload
Relay

Brake
Resistor

Temperature

Switch