Instruction manual

23
5. Motor overload protection
When using the electronic thermal relay function as motor overload protection, set the rated motor current to Pr. 9 "Electronic thermal
O/L relay".
This function detects the overload (overheat)
of the motor, stops the operation of the
inverter's output transistor, and stops the
output.
(The operation characteristic is shown on the
left)
When using the Mitsubishi constant-torque
motor
1) Set "1" or any of "13" to "16", "50", "53", "54"
in Pr. 71 . (This provides a 100% continuous
torque characteristic in the low-speed range.)
2) Set the rated current of the motor in Pr. 9.
∗1 When a value 50% of the inverter rated output
current (current value) is set in Pr. 9
∗2
The % value denotes the percentage to the
inverter rated output current. It is not the
percentage to the motor rated current.
∗3 When you set the electronic thermal relay
function dedicated to the Mitsubishi constant-
torque motor, this characteristic curve applies
to operation at 6Hz or higher.
Note
⋅ Protective function by electronic thermal relay function is reset by inverter power reset and reset signal input. Avoid
unnecessary reset and power-off.
⋅ When multiple motors are operated by a single inverter, protection cannot be provided by the electronic thermal relay
function. Install an external thermal relay to each motor.
⋅ When the difference between the inverter and motor capacities is large and the setting is small, the protective
characteristics of the electronic thermal relay function will be deteriorated. In this case, use an external thermal relay.
⋅ A special motor cannot be protected by the electronic thermal relay function. Use the external thermal relay.
Operation range
Range on the right of characteristic curve
Non-operation range
Range on the left of characteristic curve
Range for
transistor
protection
Inverter output current(%)
(% to the rated inverter current)
52.5%
105%
50
100
150
60
120
180
240
50
60
70
(min) unit display in this range
Operation time (min)
Pr. 9 = 50% setting of inverter rating*1, 2
Pr. 9 = 100% setting of inverter rating*2
(s) unit display in this range
Operation time (s)
Characteristic when electronic thermal
relay function for motor protection is turned off
(when Pr. 9 setting is 0(A))
6Hz
20Hz
10Hz
6Hz
0.5Hz
30Hz or more
*3
30Hz
or more *3
20Hz
10Hz
0.5Hz
230
Electronic thermal relay function operation characteristic
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