SOU Overvoltage Soft Stall / Limit fault in Toshiba drive
SOU Overvoltage Soft Stall / Limit fault in Toshiba drive
Description SOU is often a status alarm or a "Soft Fault." It means the Overvoltage Stall Protection has been activated. The drive is trying to decelerate the motor, but the voltage is rising too high (regenerative energy). Instead of tripping an "OP" (Overvoltage) fault and coasting, the drive automatically pauses the deceleration (holds the frequency steady) until the voltage drops. If it cannot bring the voltage down, it may eventually trip SOU. Causes
1. Aggressive Deceleration: The DEC time is set too short for the rotating mass.
2. High Line Voltage: The input AC voltage is near the upper limit of the drive's tolerance.
3. Stall Prevention Enabled: The parameter "Overvoltage Stall Protection" is turned ON (which is default). Solution This is actually the drive doing its job correctly to prevent a hard trip. However, if it prevents the machine from stopping in time, it is a problem.
To fix this, you must increase the Deceleration Time (DEC). This produces less regenerative energy. If you cannot increase the time (e.g., a safety stop is required), you MUST install a Dynamic Braking Resistor.
Once a resistor is installed, you must navigate to the "Overvoltage Stall Protection" parameter and turn it **OFF**. If you leave it ON, the drive will ignore the resistor and still perform the SOU stall behavior. By turning it OFF, you force the drive to dump the energy into the resistor, allowing for a fast, crisp stop without voltage spikes.
Description SOU is often a status alarm or a "Soft Fault." It means the Overvoltage Stall Protection has been activated. The drive is trying to decelerate the motor, but the voltage is rising too high (regenerative energy). Instead of tripping an "OP" (Overvoltage) fault and coasting, the drive automatically pauses the deceleration (holds the frequency steady) until the voltage drops. If it cannot bring the voltage down, it may eventually trip SOU. Causes
1. Aggressive Deceleration: The DEC time is set too short for the rotating mass.
2. High Line Voltage: The input AC voltage is near the upper limit of the drive's tolerance.
3. Stall Prevention Enabled: The parameter "Overvoltage Stall Protection" is turned ON (which is default). Solution This is actually the drive doing its job correctly to prevent a hard trip. However, if it prevents the machine from stopping in time, it is a problem.
To fix this, you must increase the Deceleration Time (DEC). This produces less regenerative energy. If you cannot increase the time (e.g., a safety stop is required), you MUST install a Dynamic Braking Resistor.
Once a resistor is installed, you must navigate to the "Overvoltage Stall Protection" parameter and turn it **OFF**. If you leave it ON, the drive will ignore the resistor and still perform the SOU stall behavior. By turning it OFF, you force the drive to dump the energy into the resistor, allowing for a fast, crisp stop without voltage spikes.
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