Mitsubishi Electric FR-A800, Instruction Manual

Page: 473 / 1042

Parameters (H) Protective function parameter
FR-A800 5 - 293
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.)
When setting Pr. 9 to a value (current value) of 50% of the inverter rated current
The % value denotes the percentage to the rated inverter 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 5-434.)
#
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.
I002579E
Fig. 5-121: Electronic thermal relay function operation characteristic
52.5%
105%
50
100
150 230
60
120
180
240
50
60
70
Pr. 9 = 50 % setting of
inverter rating
(mi
n
) unit displa
y
in
thi
s r
e
g
io
n
Pr. 9 = 100 % setting of
inverter rating
(s) unit displa
y
in this
re
gion
Oper
a
tion time (s)
Operation time
(min)
30 Hz
or more
20 Hz
10 Hz
6 Hz
0.5 Hz
30 Hz or more
20 Hz
10 Hz
6 Hz
0.5 Hz
Operation region
Region on the right of
characteristic curve
Non-operation region
Region on the left of character-
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
Inverter output power (%)
(% to the inverter rated current)