6-1
6. Protective Operation
6-1 List of Protective Operations
When an error occurs to the inverter, a protective function is activated to trip the inverter immediately,
displaying the name of the alarm at the LED and allowing the motor to coast to stop.
Table 6-1-1 List of alarm display and protective operations
Name of alarm
Display
Description of operation
OC1
During
acceleration
OC2
During
deceleration
Overcurrent
protection
OC3
During constant
speed operation
The protective function is activated when an overcurrent flowing
in the motor or a short circuit or ground fault in the output circuit
causes the instantaneous inverter output current to exceed the
overcurrent detection level.
OU1
During
acceleration
OU2
During
deceleration
Overvoltage
protection
OU3
During constant
speed operation
The protective function is activated when the regenerative power
from the motor increases to cause the DC link voltage of the
main circuit to exceed the overvoltage detection level (Approx.
400 Vdc for 200V class, Approx. 800V for 400V class). When an
excessive voltage is added to the source voltage, the inverter
trips due to the overvoltage, but inverter protection against the
overvoltage is impossible.
Undervoltage
protection
LU The protective function is activated when the source voltage drops to cause the DC
link voltage in the main circuit to become lower than the undervoltage detection level
(Approx. 200 Vdc for 200V class, Approx. 400V for 400V class). If F14 Restart after
momentary power failure has been selected, no alarm display is given. If the voltage
drops below the control power maintenance level, no alarm is displayed.
Input phase
loss
protection
Lin When the inverter is operated while one of the three phases of the power supply
connected to the main power supply input terminals L1/R, L2/S and L3/T of the main
circuit is missing or there is an unbalance among the three-phase voltages, the
rectifying diode or smoothing capacitor of the main circuit may be broken. The
inverter is stopped upon an alarm in these cases.
Heat sink
overheat
OH1
The protective function is activated when the temperature of the heat sink of the
inverter is high because of a broken cooling fan or for other reasons.
External alarm
input
OH2
The protective function is activated by a contact signal from an alarm contact of the
external device such as the braking unit, braking resistor, and external thermal
overload relay connected to the control circuit terminal (THR). Or an overheat
protective function is activated by the PTC thermistor.
Braking
resistor
overheat
dbH If the electronic thermal overload relay (for braking resistor) has been selected for
function code F13, the protective function is activated upon a high operation
frequency of the braking resistor to prevent the resistor from being burned due to the
temperature rise.
Motor 1
overload
OL1 If electronic thermal overload relay 1 has been selected for function code F10, the
protective function is activated by a motor current exceeding the set operation level.
Motor 2
overload
OL2 If motor 2 has been selected and driven and electronic thermal overload relay 2 has
been selected for function code A06, the protective function is activated by the
current in motor 2 exceeding the set operation level.
Inverter
overload
OLU
The protective function is activated by an output current exceeding the overload
current rating to protect the semiconductor elements in the main circuit of the
inverter from high temperatures.
Memory error
Er1 The protective function is activated by a data writing error or other errors in the
memory.
Keypad panel
communication
error
Er2 The protective function is activated when a data transmission error or transmission
stoppage is detected between the keypad panel and the control section in the
keypad panel operation mode.
CPU error Er3 The protective function is activated by electric noise or other errors developed in the
CPU, or if P24 is overloaded.
Er4 Option error
Er5
Error during operation of option
Output phase
loss
Er7 The protective function is activated during auto tuning when there is a broken wire or
no connection in the inverter output circuit.
RS485
communication
error
Er8 The protective function is activated when a communication error occurs during
communication through RS485.
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