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Motor overload protection
When using the electronic thermal relay function as motor overload protection, set the rated motor current in Pr.9
Electronic thermal O/L relay.
Operation characteristics of electronic thermal relay function
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%
100
50
Inverter output current (%)
(% to the rated output current)
NOTE
• The internal accumulated heat value of the electronic thermal relay function is reset by inverter power reset and
reset signal input. Avoid unnecessary reset and power-OFF.
• When multiple motors are driven with a single inverter or when a multi-pole motor or a special motor is driven, install
an external thermal relay (OCR) between the inverter and motors. Note that the current indicated on the motor rating
plate is affected by the line-to-line leakage current (details in the Instruction Manual (HARDWARE)) when selecting
the setting for an external thermal relay.
• The cooling effect of the motor drops during low-speed operation. Use a thermal protector or a motor with built-in
thermistor.
• 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 an external thermal relay.
• Motor over temperature sensing is not provided by the drive.
Applicable power supply
For use at an altitude above 2000 m (maximum 2500 m), only a neutral-point earthed (grounded) power supply can
be used.
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))
Range for
transistor
protection*
4
150
230
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 Electric constant-torque motor
(1) Set one of "1, 13 to 16" in Pr.71. (This provides a 100% con-
tinuous 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
current. It is not the percentage to the rated motor current.
*3
When you set the electronic thermal relay function dedicated to
the
Mitsubishi
characteristic curve applies to operation at 6 Hz or higher.
*4
Transistor
temperature of the heat sink. The protection may be activated
even with less than 150% depending on the operating
conditions.
3
Electric
constant-torque
protection
is
activated
depending
BCN-C22005-1010
motor,
this
on
the
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