6.4 Fault Detection
252
YASKAWA ELECTRIC
SIEP C710606 44B YASKAWA AC Drive T1000V Technical Manual
LED Operator Display
Fault Name
ov
Overvoltage
Voltage in the DC bus has exceeded the overvoltage detection level.
• For 200 V class: approximately 410 V
• For 400 V class: approximately 820 V (740 V when E1-01 is less than 400)
Cause
Possible Solution
Deceleration time is too short and
regenerative energy flows from the motor
into the drive.
• Increase the deceleration time (C1-02, C1-04, C1-06, C1-08).
• Install a braking resistor or a dynamic braking resistor unit.
• Enable stall prevention during deceleration (L3-04 = “1”).
Stall prevention is enabled as the default setting.
Fast acceleration time causes the motor to
overshoot the speed reference.
• Check if sudden drive acceleration triggers an overvoltage alarm.
• Increase the acceleration time.
• Use longer S-curve acceleration and deceleration times.
Excessive braking load.
The braking torque was too high, causing regenerative energy to charge the DC bus.
Reduce the braking torque, use a braking option, or lengthen decel time.
Surge voltage entering from the drive input
power.
Install a DC reactor.
Note:
Voltage surge can result from thyristor convertor and phase advancing capacitor using same
drive main input power supply.
Ground fault in the output circuit causing
the DC bus capacitor to overcharge.
• Check the motor wiring for ground faults.
• Correct grounding shorts and turn the power back on.
Improper Setting of Speed Search related
parameters. (Includes Speed Search after a
momentary power loss and after a fault
restart.)
• Check the settings for Speed Search related parameters.
• Enable Speed Search Retry function (b3-19 greater than or equal to 1 to 10).
• Adjust the current level during Speed Search and the deceleration time (b3-02 and b3-03
respectively).
• Perform Line-to-Line Resistance Auto-Tuning and then enable Speed Estimation Type Speed
Search (b3-24 = “1”).
Excessive regeneration when overshoot
occurs after acceleration.
• Enable the Overvoltage Suppression function (L3-11 = “1”).
• Lengthen the S-curve at acceleration end.
Drive input power voltage is too high.
• Check the voltage.
• Lower drive input power voltage within the limits listed in the specifications.
The dynamic braking transistor is damaged. Replace the drive.
The braking transistor is wired incorrectly.
• Check braking transistor wiring for errors.
• Properly rewire the braking resistor device.
Drive fails to operate properly due to noise
interference.
• Review the list of possible solutions provided for controlling noise.
• Review the section on handling noise interference and check the control circuit lines, main circuit
lines and ground wiring.
Load inertia has been set incorrectly.
• Check the load inertia settings when using KEB, overvoltage suppression or Stall Prevention
during deceleration.
• Adjust S6-03 (Load Inertia Ratio) in accordance with the load.
Braking function is being used in PM Open
Loop Vector Control.
Connect a braking resistor.
Motor hunting occurs.
• Adjust the parameters that control hunting.
• Set the hunting prevention gain (n1-02).
• Adjust the AFR time constant (n2-02 and n2-03) when in OLV Control.
• Use parameters n8-45 (PM Speed Feedback Detection Suppression Gain) and n8-47 (Pull-In
Current Compensation Time Constant).