Delta Electronics VFD-S manual Definition for Brake Usage ED%

Appendix B AccessoriesVFD-S Series

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%

		T1	ED% = T1/T0x100(%)
Brake Time
			T0
	Cycle Time

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.

NFB

R/L1

S/L2

T/L3

O.L.

Thermal

Overload Relay or temperature switch

MC

MC

SA

Surge

Absorber

R/L1	U/T1
S/L2	V/T2	IM
T/L3	W/T3	MOTOR
VFD Series		Thermal Overload
		Relay
	B1
		O.L.
		Brake
		BR Resistor
	B2	Temperature
		Switch

B-2 Revision August 2008, SE09, SW V2.61