LED Operator Display Fault Name
UL4
Undertorque Detection 2
The current has fallen below the minimum value set for torque detection (L6-05) for longer than the allowable time (L6-06).
Cause Possible Solution
Parameter settings are not appropriate for the type of load. Check the settings of parameters L6-05 and L6-06.
There is a fault on the machine side. Check the load for any problems.
LED Operator Display Fault Name
UL5
Mechanical Weakening Detection 2
The operation conditions matched the conditions set to L6-08.
Cause Possible Solution
Undertorque was detected and matched the condition of
mechanical loss detection operation selection (L6-08).
Check the load side for any problems.
LED Operator Display Fault Name
Uv1
DC Bus Undervoltage
One of the following conditions occurred while the drive was stopped:
• Voltage in the DC bus fell below the undervoltage detection level (L2-05).
• For 200 V class: approximately 190 V (160 V for single phase drives)
• For 400 V class: approximately 380 V (350 V when E1-01 is less then 400) The fault is output only if L2-01 = 0 or L2-01 = 1 and
the DC bus voltage is under L1-05 for longer than L2-02.
Cause Possible Solution
Input power phase loss.
• The main circuit drive input power is wired incorrectly.
• Correct the wiring.
One of the drive input power wiring terminals is loose.
• Ensure there are no loose terminals.
• Apply the tightening torque specified in this manual to fasten the terminals. Refer to Wire Size and Torque Specifications on page
46
There is a problem with the voltage from the drive input
power.
• Check the voltage.
• Correct the voltage to within range listed in drive input power specifications.
The power has been interrupted. Correct the drive input power.
Drive internal circuitry has become worn.
• Check the maintenance time for the capacitors (U4-05).
• Replace the drive if U4-05 exceeds 90%.
The drive input power transformer is not large enough and
voltage drops after switching on power.
Check the capacity of the drive input power transformer.
Air inside the drive is too hot. Check the drive internal temperature.
Problem with the CHARGE indicator. Replace the drive.
LED Operator Display Fault Name
Uv2
Control Power Supply Voltage Fault
Voltage is too low for the control drive input power.
Cause Possible Solution
L2-02 changed from its default value in drive that is 7.5 kW
or smaller without installing a Momentary Power Loss Ride-
Thru.
Correct parameter L2-02 setting or install optional Momentary Power Loss Ride-Thru unit.
The wiring for the control power supply is damaged.
• Cycle power to the drive. Check if the fault reoccurs.
• Replace the drive if the fault continues to occur.
Internal circuitry is damaged.
• Cycle power to the drive. Check if the fault reoccurs.
• Replace the drive if the fault continues to occur.
LED Operator Display Fault Name
Uv3
Undervoltage 3 (Inrush Prevention Circuit Fault)
The inrush prevention circuit has failed.
Cause Possible Solution
The contactor on the inrush prevention circuit is damaged.
• Cycle power to the drive. Check if the fault reoccurs.
• Replace the drive if the fault continues to occur.
• Check monitor U4-06 for the performance life of the inrush prevention circuit.
• Replace the drive if U4-06 exceeds 90%.
6.4 Fault Detection
YASKAWA ELECTRIC SIEP C710606 18A YASKAWA AC Drive – V1000 Technical Manual (Preliminary)
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Troubleshooting
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