YASKAWA Varispeed L7, Instruction Manual, Page: 216 / 243

Troubleshooting
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If There is Low Speed Control Accuracy Above Base Speed in Open Loop
Vector Control Mode
The Inverter’s maximum output voltage is determined by its input voltage. (For example, if 400 VAC is input,
then the maximum output voltage will be 400 VAC). Vector control uses voltage to control the currents within
the motor. If the vector control voltage reference value exceeds the Inverter output voltage capability, the
speed control accuracy will decrease because the motor currents cannot be properly controlled. Use a motor
with a low rated voltage compared to the input voltage, or change to Closed Loop Vector control.
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If Motor Deceleration is Slow
The following causes are possible:
„ The deceleration time is too long.
The following causes are possible:
The deceleration time setting is too long.
Check the deceleration time setting (parameters C1-02, C1-04, C1-06, and C1-08).
Motor torque is insufficient.
If the parameters are correct and there is no overvoltage fault, then the motor's power may be insufficient.
Consider increasing the motor and Inverter capacity.
The torque limit has been reached.
When a torque limit is reached (L7-01 to L7-04), the motor torque will be limited. This can cause the deceler-
ation time to be extended. Check to be sure that the value set for the torque limit is suitable.
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