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Selection and protection of a motor
(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.
Pr. 450
Pr. 9
Second applied
Electronic
motor
thermal O/L relay
9999
0
9999
Other than 0
Other than 9999
0
Other than 9999
Other than 0
... 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.
REMARKS
The RT signal acts as the second function selection signal and makes the other second functions valid. (Refer to page 119.)
(3) Electronic thermal relay function pre-alarm (TH) and alarm signal (THP signal)
The alarm signal (THP) is output and electronic thermal relay function pre-alarm (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 setting electronic-thermal relay protection (E.THM/E.THT) occurs.
The inverter output is not shut off even when the alarm signal (THP) is output.
For the terminal used for the THP signal output, assign the function by setting "8 (positive logic) or 108 (negative logic)" in
Pr. 190, Pr. 192 or Pr. 197 (output terminal function selection).
100%: Electronic thermal O/L relay alarm operation value
NOTE
Changing the terminal assignment using Pr.190, Pr.192, and Pr.197 (output terminal function selection) may affect the other
functions. Set parameters after confirming the function of each terminal.
(4) External thermal relay input (OH signal)
Thermal relay
protector
Inverter
U
V
W
OH
SD
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. Set parameters after confirming the function of each terminal.
104
Pr.51
Second electronic
thermal O/L relay
9999
0
0.01 to 500
9999
0
0.01 to 500
9999
0
0.01 to 500
9999
0
0.01 to 500
Electronic thermal
relay function
operation level
Electronic thermal
O/L relay alarm
(THP)
To protect the motor against overheat, use the OH signal when using an external
thermal relay or the built-in thermal protector of the motor.
Motor
When the thermal relay operates, the inverter output is shut off and outputs the fault
IM
signal (E.OHT).
For the terminal used for OH signal input, assign the function by setting "7" in any of
Pr. 178 to Pr.182 (input terminal function selection).
RT = OFF
RT = ON
First
Second
First
Second
motor
motor
motor
motor
OFF
ON
ON
U
V
W
RT
SD
100%
85%
Time
MC
IM
MC
IM
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