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101
Selection and protection of a motor
4
PARAMETERS
(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.
(3) Electronic thermal relay function prealarm (TH) and alarm signal (THP signal)
(4) External thermal relay input (OH signal)
Pr. 450
Second applied
motor
Pr. 9
Electronic
thermal O/L relay
Pr.51
Second electronic
thermal O/L relay
RT = OFF RT = ON
First
motor
Second
motor
First
motor
Second
moto
r
9999 0
9999 ××××
0 ××××
0.01 to 500 ×∆×
9999 Other than 0
9999 × ×
0 ×∆×
0.01 to 500 ∆∆
Other than 9999 0
9999 ××××
0 ××××
0.01 to 500 ×∆×
Other than 9999 Other than 0
9999 ∆∆
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.
REMARKS
The RT signal acts as the second function selection signal and makes the other second functions valid. (Refer to page 116)
100%: Electronic thermal O/L relay alarm operation value
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 setting
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
the function by setting "8 (positive logic) or 108
(negative logic)" in Pr. 190 or Pr. 192 (output terminal
function selection) .
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.
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.
When the thermal relay operates, the inverter trips and outputs the fault 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) .
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.
RT
SD
MC
MC
W
V
U
IM
IM
Electronic thermal
relay function
operation level
Electronic thermal
O/L relay alarm
(THP)
OFF
ON
100%
85%
Time
ON
Inverter
U
V
W
OH
SD
Thermal relay
protector
Moto
r
IM