Mitsubishi Electric FR-A820-00046 Instruction Manual page 506

(H) Protective function parameter
Electronic thermal O/L relay operation characteristic for induction motor (Pr. 9, E.THM)
● This function detects the overload (overheat) of the motor and trips the inverter by stopping the
operation of the transistor at the inverter output side.
● Set the rated current (A) of the motor in Pr. 9. (If the motor has both 50 Hz and 60 Hz ratings and
the Pr. 3 "Base frequency" is set to 60 Hz, set to 1.1 times the 60 Hz rated motor current.)
● Set "0" in Pr. 9 to avoid activating the electronic thermal O/L 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))
● When using the Mitsubishi constant-torque motor, set Pr. 71 "Applied motor" = "1, 13 to 16, 50,
53, 54". (This will set a 100% continuous torque characteristic in the low-speed range.)
Fig. 5-121:
When setting Pr. 9 to a value (current value) of 50% of the inverter rated current
The % value denotes the percentage to the inverter rated current. It is not the percentage to the
rated motor current.
When the electronic thermal O/L relay of the Mitsubishi constant-torque motor is set, the charac-
teristic curve is as shown in this diagram at 6 Hz or higher. (For selection of the operation
characteristic, refer to page 5-451.)
Transistor protection is activated depending on the temperature of the heatsink. The protection
may be activated even with less than 150% depending on the operating conditions.
5 - 304
Pr. 9 = 50 % setting of
inverter rating
70
30 Hz
or more
20 Hz
60
10 Hz
6 Hz
0.5 Hz
50
240
180
120
60
52.5% 105%
50
Inverter output power (%)
(% to the inverter rated current)
Electronic thermal relay function operation characteristic
Pr. 9 = 100 % setting of
inverter rating
30 Hz or more
20 Hz
Operation region
Region on the right of
10 Hz
characteristic curve
6 Hz
Non-operation region
Region on the left of character-
0.5 Hz
istic 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
100
150 230
Parameters
I002579E