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(5) Motor overload protection
This inverter is certified as a motor overload protection device by UL.
When using the electronic thermal relay function as motor overload protection, set the rated motor current to Pr. 9
Electronic thermal O/L relay.
Electronic thermal relay function operation characteristic
Pr. 9 = 50% setting of
inverter rating*
1.2
70
30Hz
or more*
3
20Hz
60
10Hz
6Hz
0.5Hz
50
240
180
120
60
105%
52.5%
50
Inverter output power (%)
(% to the rated input current)
CAUTION
⋅ 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.
⋅ Electronic thermal relay does not function when 5% or less of inverter rated current is set to electronic thermal relay setting.
Pr. 9 = 100% setting
of inverter rating*
1.2
30Hz or more*
3
20Hz
Operation range
Range on the right of
10Hz
characteristic curve
6Hz
Non-operation range
Range on the left of
0.5Hz
characteristic curve
Characteristic when
electronic thermal relay
function for motor
protection is turned off
(When Pr. 9 setting is 0(A))
For transistor protection
Electronic thermal relay
function
100
150
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 "18", "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.
191

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