bF Brake Transistor Fault fault in delta drive

bF Brake Transistor Fault fault in delta drive troubleshooting

Description

The bF fault refers to the internal "Brake Chopper" IGBT. This component switches on to dump excess energy into the braking resistor. If the drive detects that this transistor is stuck "ON" (shorted) or stuck "OFF" (open) when it should be switching, bF is displayed.

Causes

1. Transistor Short: The internal braking IGBT has fused shut. This is dangerous as it will permanently connect the DC bus to the resistor, causing the resistor to glow red hot and potentially catch fire.
2. Resistor Short: The external braking resistor has shorted out, drawing infinite current through the chopper.
3. Overworking: The braking duty cycle exceeded the transistor's thermal rating.

Solution

Hardware inspection:
1. Check Resistor: Disconnect the resistor and measure its resistance. If it is near 0 Ohms, replace it.
2. Check Drive Output: With power off, check continuity between the B1 and B2 terminals (or + and B2). It should be Open. If it is Shorted, the drive is damaged and needs repair.
3. Safety: If you suspect bF, remove power immediately to prevent the braking resistor from causing a fire.