Mitsubishi Electric FR-D720-070 Instruction Manual page 106

(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 to Pr. 51.
When the RT signal is on, thermal protection is provided based on the Pr. 51 setting.
For the terminal used for RT signal input, set "3" in any of Pr. 178 to Pr. 182 (input terminal function selection) to assign the function.
MC Pr. 450
Second applied
IM
motor
MC
U
9999
V
IM
W
RT 9999
SD
Other than 9999
Other than 9999
REMARKS
The RT signal acts as the second function selection signal and makes the other second functions valid. (Refer to page 116)
(3) Electronic thermal relay function prealarm (TH) and alarm signal (THP signal)
100%: Electronic thermal O/L relay alarm operation value
Electronic thermal
relay function
operation level
Electronic thermal
O/L relay alarm
OFF
ON
(THP)
NOTE
Changing the terminal assignment using Pr.190, Pr.192 (output terminal function selection) may affect the other functions.
Make setting after confirming the function of each terminal.
(4) External thermal relay input (OH signal)
To protect the motor against overheat, use the OH signal when using an external
Thermal relay
thermal relay or the built-in thermal protector of the motor.
protector
Inverter
Motor
When the thermal relay operates, the inverter trips and outputs the fault signal
U
V
IM
(E.OHT).
W
OH For the terminal used for OH signal input, assign the function by setting "7" in any of
SD
Pr. 178 to Pr.182 (input terminal function selection) .
External thermal relay input
connection example
NOTE
Changing the terminal assignment using Pr. 178 to Pr. 182 (input terminal function selection) may affect the other
functions. Make setting after confirming the function of each terminal.
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Selection and protection of a motor
Pr. 9 Pr.51
Electronic Second electronic First
thermal O/L relay thermal O/L relay
motor
9999
0 0
0.01 to 500
9999
Other than 0 0
0.01 to 500
9999
0 0
0.01 to 500
9999
Other than 0 0
0.01 to 500
... Output current value is used to perform integration processing.
∆... Output current is assumed as 0A to perform integration processing. (cooling processing)
×... Electronic thermal relay function is not activated.
The alarm signal (THP) is output and electronic thermal
relay function prealarm (TH) is displayed when the
electronic thermal O/L relay cumulative value reaches
85% of the level set in Pr. 9 or Pr. 51. If it reaches 100%
of the Pr. 9 Electronic thermal O/L relay
100%
85%
electronic-thermal relay protection (E.THM/E.THT)
occurs.
The inverter does not trip even when the alarm signal
(THP) is output.
For the terminal used for the THP signal output, assign
ON
Time
the function by setting "8 (positive logic) or 108
(negative logic)" in Pr. 190 or Pr. 192 (output terminal
function selection) .
RT = OFF RT = ON
Second First Second
motor motor motor
× × × ×
× × × ×
× ∆ ×
× ×
× ∆ ×
∆ ∆
× × × ×
× × × ×
× ∆ ×
∆ ∆
× ∆ ×
∆ ∆
setting
4
101