db Braking Transistor fault in Toshiba drive
db Braking Transistor Fault fault in Toshiba drive
Description The "db" fault indicates a failure in the Dynamic Braking circuit. Unlike "OLr" (which is a thermal overload calculation for the resistor), "db" is a hardware check of the internal IGBT chopper or the external resistor. The drive measures the resistance across the PA/+ and PB terminals during startup. If it detects a short circuit or excessively low resistance, it trips "db" to prevent the braking transistor from blowing up the moment it attempts to fire. Causes
1. Resistor Short: The external dynamic braking resistor has physically failed, and the internal coils are touching the casing (ground) or each other, reducing resistance to near zero.
2. Internal IGBT Failure: The braking transistor inside the drive (which switches the resistor on/off) has fused closed (shorted).
3. Wiring Error: The resistor was wired to the wrong terminals (e.g., across Positive and Negative bus instead of PA and PB).
4. Wrong Parameter: The "Braking Resistance" parameter is set lower than the drive's minimum allowable resistance. Solution Power down immediately. Disconnect the external resistor cables from the PA and PB terminals.
1. Measure the external resistor with a multimeter (Ohms). Compare this reading to the minimum allowed resistance specified in the Toshiba manual for your drive size. If your resistor measures 10 ohms, but the manual says "Min Resistance: 20 Ohms," the drive interprets this as a short. You must upgrade the resistor.
2. With the resistor disconnected, measure the resistance of the PA and PB terminals on the drive itself. It should be open circuit (Mega-ohms). If you read 0 ohms on the drive terminals with no wires attached, the internal braking IGBT is destroyed. The drive needs repair.
3. If using a drive *without* a resistor, ensure the "Dynamic Braking" parameter is set to Disable. If enabled with no resistor, some older firmware versions may trip depending on stray capacitance.
Description The "db" fault indicates a failure in the Dynamic Braking circuit. Unlike "OLr" (which is a thermal overload calculation for the resistor), "db" is a hardware check of the internal IGBT chopper or the external resistor. The drive measures the resistance across the PA/+ and PB terminals during startup. If it detects a short circuit or excessively low resistance, it trips "db" to prevent the braking transistor from blowing up the moment it attempts to fire. Causes
1. Resistor Short: The external dynamic braking resistor has physically failed, and the internal coils are touching the casing (ground) or each other, reducing resistance to near zero.
2. Internal IGBT Failure: The braking transistor inside the drive (which switches the resistor on/off) has fused closed (shorted).
3. Wiring Error: The resistor was wired to the wrong terminals (e.g., across Positive and Negative bus instead of PA and PB).
4. Wrong Parameter: The "Braking Resistance" parameter is set lower than the drive's minimum allowable resistance. Solution Power down immediately. Disconnect the external resistor cables from the PA and PB terminals.
1. Measure the external resistor with a multimeter (Ohms). Compare this reading to the minimum allowed resistance specified in the Toshiba manual for your drive size. If your resistor measures 10 ohms, but the manual says "Min Resistance: 20 Ohms," the drive interprets this as a short. You must upgrade the resistor.
2. With the resistor disconnected, measure the resistance of the PA and PB terminals on the drive itself. It should be open circuit (Mega-ohms). If you read 0 ohms on the drive terminals with no wires attached, the internal braking IGBT is destroyed. The drive needs repair.
3. If using a drive *without* a resistor, ensure the "Dynamic Braking" parameter is set to Disable. If enabled with no resistor, some older firmware versions may trip depending on stray capacitance.
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