Mitsubishi Electric 800 Series Instruction Manual (Function page 279

• When using the Mitsubishi Electric constant-torque motor, set the constant-torque motor in Pr.71 Applied motor referring
to page 380. (This setting enables the 100% constant-torque characteristic in the low-speed range.)
Pr. 9 = 50% setting
of inverter rating*
70
30Hz
or more*
20Hz
60
10Hz
6Hz
0.5Hz
50
240
180
120
60
52.5%
*1 When setting Pr.9 to a value (current value) of 50% of the inverter rated current
*2 The % value denotes the percentage to the rated inverter current. It is not the percentage to the rated motor current.
*3 When the electronic thermal relay function dedicated to the Mitsubishi Electric constant-torque motor is set, this characteristic curve applies to
operation. (For selection of the operation characteristic, refer to
*4 Transistor protection is activated depending on the temperature of the heat sink. The protection may be activated even with less than 150%
depending on the operating conditions.
NOTE
• The internal accumulated heat value of the electronic thermal relay function is reset to the initial value by the inverter's power
reset or reset signal input. Avoid unnecessary reset and power-OFF.
• Install an external thermal relay (OCR) between the inverter and motors to operate several motors, a multi-pole motor or a
dedicated motor with one inverter. When setting an external thermal relay, note that the current indicated on the motor rating
plate is affected by the line-to-line leakage current. The cooling effect of the motor drops during low-speed operation. Use a
motor with built-in thermal protector. (For details of the line-to-line leakage current, refer to the Instruction Manual
(Connection).)
• When the difference between the inverter and motor capacities is large and the set value is small, the protective characteristics
of the electronic thermal relay function will be deteriorated. Use an external thermal relay in such cases.
• A dedicated motor cannot be protected by an electronic thermal O/L relay. Use an external thermal relay.
• The transistor protection thermal O/L relay is activated early when the Pr.72 PWM frequency selection setting is increased.
 Electronic thermal O/L relay when using PM motor (Pr.9)
• This function detects the overload (overheat) of the motor and shut off the inverter output by stopping the operation of the
transistor at the inverter output side.
• Set the rated current (A) of the motor in Pr.9 Electronic thermal O/L relay.
• Set "0" in Pr.9 to avoid activating the electronic thermal relay function; for example, when using an external thermal relay
for the motor.
(Note that the output transistor protection of the inverter is activated. (E.THT))
278
12. (H) Protective Function Parameters
12.1 Motor overheat protection (electronic thermal O/L relay)
Pr. 9 = 100% setting
of inverter rating*
1.2
30Hz or more* 3
20Hz
3 Operation region
Region on the right of
10Hz
characteristic curve
6Hz
Non-operation region
Region 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
the transistor
protection
105%
100
50 150
Inverter output power (%)
(% to the inverter rated current)
1.2
*4
230
page 380.)