Mitsubishi Electric FR-A700 Technical Manual page 345

2.17.3 Motor overheat protection (Electronic thermal O/L relay) [Pr. 9, 51, 875
common
(common)
Set the current of the electronic thermal relay function to
protect the motor from overheat. This feature provides the
optimum protective characteristics, including reduced
motor cooling capability, at low speed. Refer to page 50 to
[Pr. ] Name Initial Value
Electronic thermal Rated inverter
9
O/L relay output current*
Second electronic
51
thermal O/L relay
875 Fault definition
* The 0.4K and 0.75K are set to 85% of the rated inverter current on
(1) Electronic thermal O/L relay [Pr. 9]
This function detects the overload (overheat) of the
motor and trips. (Refer to page 111.)
Set the motor type to be used in [Pr. 71] and set the
rated motor current value (A) in [Pr. 9].
(If the motor has both 50Hz and 60Hz rating and the [Pr.
3 Base frequency] is set to 60Hz, set the 1.1 times of the
60Hz rated motor current.)
Set [Pr. 9 = 0] when you do not want to operate the
electronic thermal relay function when using the motor
with the external thermal relay, etc. (Note that the output
transistor protection of the inverter functions (E.THT).)
Since a thermal relay protector is built in a motor
dedicated for vector control (SF-V5RU), set [Pr. 9 = 0] to
use the motor.
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
function. Install an external thermal relay to each motor.
When a 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.
Electronic thermal may not operate when the setting
value for the electronic thermal is 5% of the inverter's
rated current or less.
A special motor cannot be protected by the electronic
thermal relay function. Use an external thermal relay.
Setting Range
55K or less 0 to 500A
75K or more 0 to 3600A
55K or less 0 to 500A
9999 75K or more 0 to 3600A
9999
0
0
1
(*[Pr. 875] is not available for
protect the motor from overheat using external thermal
input (OH signal) and refer to page 50 using PTC
thermistor input (PTC signal).
Description
Set the rated motor current.
Made valid when the RT signal is ON.
Set the rated motor current.
Second electronic thermal O/L relay invalid
Normal operation
The motor decelerates to stop when motor
thermal protection is activated.
.
A700 E700
(2) Set two different electronic thermal O/L
relays [Pr. 51]
Use this function when running two motors of
different rated currents individually by a single
inverter. (When running two motors together, use
external thermal relays.)
Set the rated current of the second motor in [Pr. 51].
When the RT signal is ON, thermal protection is
provided based on the [Pr. 51] setting. The RT signal
acts as the second function selection signal and
makes the other second functions valid.
U
V
W
RT
SD
379
PARAMETER
* ]
.)
F700 E700 D700
Available
Inverter
F700
A700 E700
D700
—
MC
IM
MC
IM
2