Mitsubishi Electric 800 Series Instruction Manual page 25

 Regenerative overvoltage trip during deceleration or stop
Operation panel
indication
If regenerative power causes the inverter's internal main circuit DC voltage to reach or exceed the specified
Description value, the protection circuit is activated to stop the inverter output. The circuit may also be activated by a surge
voltage produced in the power supply system.
• Check for sudden speed reduction.
Check point
• Check if the stall prevention operation is frequently activated in an application with a large load inertia.
• Set the deceleration time longer. (Set the deceleration time which matches the moment of inertia of the load.)
• Make the brake cycle longer.
Corrective action • Use the regeneration avoidance function (Pr.882, Pr.883, Pr.885, and Pr.886).
• Use the brake unit or multifunction regeneration converter (FR-XC) as required.
• Set Pr.154 Voltage reduction selection during stall prevention operation = "11".
Reference FR-E800 Instruction Manual (Function)
 Inverter overload trip (Electronic thermal O/L relay)
Resetting the inverter initializes the internal cumulative heat value of the electronic thermal O/L relay function.
Operation panel
indication
If the temperature of the output transistor elements exceeds the protection level with a rated output current or
Description
higher flowing without the overcurrent trip (E.OC[]), the inverter output is stopped. (Overload capacity 150% 60 s)
• Check that acceleration/deceleration time is not too short.
• Check that torque boost setting is not too large (small).
Check point
• Check that load pattern selection setting is appropriate for the load pattern of the using machine.
• Check the motor for the use under overload.
• Set the acceleration/deceleration time longer.
• Adjust the torque boost setting.
Corrective action
• Set the load pattern selection setting according to the load pattern of the using machine.
• Reduce the load.
Reference FR-E800 Instruction Manual (Function)
 Motor overload trip (electronic thermal relay function)
Resetting the inverter initializes the internal cumulative heat value of the electronic thermal relay function.
Operation panel
indication
The electronic thermal O/L relay function in the inverter detects motor overheat, which is caused by overload or
reduced cooling capability during low-speed operation. When the cumulative heat value reaches 85% of the Pr.9
Electronic thermal O/L relay setting, pre-alarm (TH) is output. When the accumulated value reaches the
Description
specified value, the protection circuit is activated to stop the inverter output. When the inverter is used to drive a
dedicated motor, such as a multiple-pole motor, or several motors, the motor cannot be protected by the
electronic thermal O/L relay. Install an external thermal relay on the inverter output side.
• Check the motor for the use under overload.
Check point • Check that the setting of Pr.71 Applied motor for motor selection is correct.
• Check that the stall prevention operation setting is correct.
• Reduce the load.
Corrective action • For a constant-torque motor, set the constant-torque motor in Pr.71.
• Set the stall prevention operation level accordingly.
Reference FR-E800 Instruction Manual (Function)
 Heat sink overheat
Operation panel
indication
When the heatsink overheats, the temperature sensor is activated, and the inverter output is stopped.
The FIN signal can be output when the temperature becomes approximately 85% of the heatsink overheat
Description protection operation temperature.
For the terminal used for the FIN signal output, assign the function by setting "26 (positive logic) or 126 (negative
logic)" from Pr.190 to Pr.196 (Output terminal function selection).
• Check for too high surrounding air temperature.
• Check for heatsink clogging.
Check point
• Check that the cooling fan is not stopped. (Check that FN is not displayed on the operation panel.)
• Check that the cooling fan is installed in correct orientation.
• Set the surrounding air temperature to within the specifications.
• Clean the heatsink.
Corrective action
• Replace the cooling fan.
• Install the cooling fan in correct orientation.
Reference FR-E800 Instruction Manual (Function)
E.OV3
E.THT
E.THM
E.FIN
2. Protective Functions
2.5 Causes and corrective actions
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