6-11
Chap. 6 TROUBLESHOOTING
Possible Causes What to Check and Suggested Measures
(2) A surge current entered the
input power supply.
In the same power line, if a phase-advancing capacitor is turned ON/OFF or a
thyristor converter is activated, a surge (momentary large increase in the voltage or
current) may be caused in the input power.
Î Install a DC reactor.
(3) The deceleration time was too
short for the moment of inertia
for load.
Recalculate the deceleration torque based on the moment of inertia for the load and
the deceleration time.
Î Increase the deceleration time (F08, E11, E13, E15, and H56).
Î Enable the automatic deceleration (anti-regenerative control) (H69), or
deceleration characteristics (H71).
Î Enable torque limiter (F40, F41, E16, E17, and H73).
Î Set the rated voltage (at base frequency) (F05*) to "0" to improve the braking
capability.
Î Consider the use of a braking resistor.
(4) The acceleration time was too
short.
Check if the overvoltage alarm occurs after rapid acceleration.
Î Increase the acceleration time (F07, E10, E12, and E14).
Î Select the S-curve pattern (H07).
Î Consider the use of a braking resistor.
(5) Braking load was too heavy. Compare the braking torque of the load with that of the inverter.
Î Set the rated voltage (at base frequency) (F05*) to "0" to improve the braking
capability.
Î Consider the use of a braking resistor.
(6) Malfunction caused by noise. Check if the DC link bus voltage was below the protective level when the
overvoltage alarm occurred.
Î Implement noise control measures. For details, refer to the FRENIC-MEGA
User's Manual, "Appendix A."
Î Enable the auto-reset (H04).
Î Connect a surge absorber to magnetic contactor's coils or other solenoids (if
any) causing noise.
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Undervoltage
Problem DC link bus voltage has dropped below the undervoltage detection level.
Possible Causes What to Check and Suggested Measures
(1) A momentary power failure
occurred.
Î Release the alarm.
Î If you want to restart running the motor without treating this condition as an
alarm, set F14 to "3," "4," or "5," depending on the load type.
(2) The power to the inverter was
switched back to ON too soon
(when F14 = 1).
Check if the power to the inverter was switched back to ON while the control power
was still alive. (Check whether the LEDs on the keypad light.)
Î Turn the power ON again after all LEDs on the keypad go off.
(3) The power supply voltage did
not reach the inverter's
specification range.
Measure the input voltage.
Î Increase the voltage to within the specified range.
(4) Peripheral equipment for the
power circuit malfunctioned, or
the connection was incorrect.
Measure the input voltage to find which peripheral equipment malfunctioned or
which connection is incorrect.
Î Replace any faulty peripheral equipment, or correct any incorrect connections.
(5) Any other loads connected to
the same power supply has
required a large starting
current, causing a temporary
voltage drop.
Measure the input voltage and check the voltage fluctuation.
Î Reconsider the power supply system configuration.
(6) Inverter's inrush current caused
the power voltage drop because
the power supply transformer
capacity was insufficient.
Check if the alarm occurs when a molded case circuit breaker (MCCB),
residual-current-operated protective device (RCD)/earth leakage circuit breaker
(ELCB) (with overcurrent protection) or magnetic contactor (MC) is turned ON.
ÎReconsider the capacity of the power supply transformer.
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Input phase loss
Problem Input phase loss occurred, or interphase voltage unbalance rate was large.
Possible Causes What to Check and Suggested Measures
(1) Breaks in wiring to the main
power input terminals.
Measure the input voltage.
Î Repair or replace the main circuit power input wires or input devices (MCCB,
MC, etc.).
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