Mitsubishi Electric FR-A720-0.4K Instruction Manual page 188

Selection and protection of a motor
(3) Set multiple electronic thermal relay functions (Pr. 51)
Use this function when rotating two motors of different rated currents individually by a
single inverter. (When rotating 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.
Pr. 450 Pr. 9
Second applied Electronic thermal
motor O/L relay
9999 0
Other than
9999
0
Other than
0
9999
Other than Other than
9999 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 226)
⋅ The RT signal is assigned to the RT terminal in the initial setting. By setting "3" in any of Pr. 178
to Pr. 189 (input terminal function selection), you can assign the RT signal to the other terminal.
(4) Electronic thermal relay function alarm output and alarm signal (THP signal)
100%: Electronic thermal relay function alarm operation value
Electronic thermal
relay function
operation level
Electronic thermal O/L
(THP)
relay alarm
OFF
CAUTION
⋅ Changing the terminal assignment using Pr. 190 to Pr. 196 (output terminal function selection) may affect the other functions. Make
setting after confirming the function of each terminal.
(5) External thermal relay input (OH signal)
Thermal relay protector
Inverter
Motor
U
V
IM
W
OH
SD
External thermal relay input
connection example
178
Pr. 51
First
Second electronic thermal O/L
relay
motor
9999
0
0.01 to 500 (0.1 to 3600)
9999
0
0.01 to 500 (0.1 to 3600)
9999
0
0.01 to 500 (0.1 to 3600)
9999
0
0.01 to 500 (0.1 to 3600)
⋅ The alarm signal (THP) is output when the electronic thermal
100%
85%
⋅ The inverter does not shut off the output if the alarm signal is
ON
ON
Time
⋅ For the terminal used for the THP signal output, assign the
⋅ 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 shuts off the output and outputs the
alarm signal (E.OHT).
⋅ For the terminal used for OH signal input, assign the function by setting "7" in any
of Pr. 178 to Pr. 189 (input terminal function selection)
RT = OFF RT = ON
Second First Second
motor motor motor
× × ×
× × ×
× ×
×
×
× × ×
× × ×
× ×
×
relay function 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 function protection (E.
THM/E.THT) occurs.
output.
function by setting "8" (positive logic) or "108" (negative logic) in
any of Pr. 190 to Pr. 196 (output terminal function selection).
MC
MC
U
V
W
RT
×
SD
×
×
×
×
×
×
IM
IM