1. Recheck all wiring and connections before applying power to the inverter.
2. Operation of the HBU is automatic once installed. It will turn on when the voltage of the inverter DC Bus
exceeds the activation voltage setting. When activated, the HBU draws current off the DC Bus and passes it to
the braking resistor(s). In so doing, it will dissipate the regenerative energy from the motor load as heat.
3. Do not touch the braking resistor while the inverter is operating. The resistor may become very hot during
4. Inside the HBU front metal cover, on the internal printed circuit board, there are two LED indicators. The red
LED – "POWER" – will be ON when the voltage between the DC Bus P and N of inverter is higher than 35V;
and the green LED – "BRAKING" – will be ON when the DC bus level is above the activation voltage and the
braking unit is therefore passing current to the resistor(s).
Do not disassemble the HBU when it is connected to an inverter and the power is applied!
Do not touch the braking resistor while the inverter is energized. Its surface may be very hot during
normal operation, and there is risk of injury.
Hitachi America, Ltd.