UP (UP1) Undervoltage Protection fault in Toshiba drive
UP (UP1) Undervoltage Protection fault in Toshiba drive
Description UP indicates the DC bus voltage has dropped below the operational floor. The VFD logic circuits (the "brain") run off a switched-mode power supply fed by the DC bus. If the voltage drops too low, the brain will die. The UP fault is a warning that power is insufficient to maintain motor torque. This usually happens when the main power is cut, but if it happens while running, it's a problem. Causes
1. Brownout: The facility voltage has sagged significantly (e.g., heavy machinery starting nearby).
2. Contactor Issues: A pre-charge contactor inside the drive (or external) failed to close, or contacts are bouncing.
3. Internal Circuit Failure: The "Soft Charge" resistor or relay inside the drive has failed.
4. Loose Input Wiring: High resistance connections causing voltage drop under load. Solution Measure the input voltage L1, L2, L3. Ensure it is within the drive's tolerance (usually +/- 10% of rated voltage). If the input voltage is solid 480V/230V, monitor the voltage *while* the motor starts. If the voltage sags significantly only when the motor starts, your feed transformer is undersized or the supply cables are too thin (gauge is too small), causing voltage drop.
If the fault occurs immediately upon power up, listen for a "click" inside the drive a few seconds after power is applied. This is the bypass contactor shorting out the charging resistors. If you don't hear the click, or if the drive powers up and then trips UP as soon as you press Run, the internal soft-charge circuit is damaged. This requires drive repair or replacement.
If your facility experiences frequent short power dips, you can adjust the "Undervoltage Stall" or "Ride Through" parameters. This tells the drive to use the kinetic energy of the spinning motor (regeneration) to keep the DC bus charged during a brief power loss, keeping the control board alive until power returns.
Description UP indicates the DC bus voltage has dropped below the operational floor. The VFD logic circuits (the "brain") run off a switched-mode power supply fed by the DC bus. If the voltage drops too low, the brain will die. The UP fault is a warning that power is insufficient to maintain motor torque. This usually happens when the main power is cut, but if it happens while running, it's a problem. Causes
1. Brownout: The facility voltage has sagged significantly (e.g., heavy machinery starting nearby).
2. Contactor Issues: A pre-charge contactor inside the drive (or external) failed to close, or contacts are bouncing.
3. Internal Circuit Failure: The "Soft Charge" resistor or relay inside the drive has failed.
4. Loose Input Wiring: High resistance connections causing voltage drop under load. Solution Measure the input voltage L1, L2, L3. Ensure it is within the drive's tolerance (usually +/- 10% of rated voltage). If the input voltage is solid 480V/230V, monitor the voltage *while* the motor starts. If the voltage sags significantly only when the motor starts, your feed transformer is undersized or the supply cables are too thin (gauge is too small), causing voltage drop.
If the fault occurs immediately upon power up, listen for a "click" inside the drive a few seconds after power is applied. This is the bypass contactor shorting out the charging resistors. If you don't hear the click, or if the drive powers up and then trips UP as soon as you press Run, the internal soft-charge circuit is damaged. This requires drive repair or replacement.
If your facility experiences frequent short power dips, you can adjust the "Undervoltage Stall" or "Ride Through" parameters. This tells the drive to use the kinetic energy of the spinning motor (regeneration) to keep the DC bus charged during a brief power loss, keeping the control board alive until power returns.
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