25
APPENDIX
Wiring protection
Provide the appropriate UL and cUL listed class T type fuse that are suitable for branch circuit protection in accordance
with the table below
* Maximum allowable rating by US National Electrical Code. Exact size must be chosen for each installation.
Motor overload protection
When using the electronic thermal relay as motor overload protection, set the rated motor current to
Pr. 9 Electronic thermal
O/L relay
.
Electronic thermal relay function characteristic
This function detects the overload (overheat) of the
motor, stops the operation of the inverter's output
transistor, and stops the output.
When using the Mitsubishi constant-torque motor set
"1" or any of "13 to 18", "50", "53" or "54" in Pr. 71. This
provides a 100 % continuous torque characteristic in
the low-speed range. Set the rated current of the motor
in Pr. 9.
*1
When a value 50 % of the inverter rated output current (current
value) is set in Pr. 9.
*2
The % value denotes the percentage to the inverter rated
output current. It is not the percentage to the motor rated
current.
*3
When you set the electronic thermal relay function
dedicated to the Mitsubishi constant-torque motor, this
characteristic curve applies to operation at 6 Hz or higher.
A.1.3 Short circuit ratings
Suitable for use in a circuit capable of delivering not more than 5 kA rms symmetrical amperes, 528 V maximum.
FR-A741-
-K
5.5
7.5
11
15
018.5
22
30
37
45
55
Rated voltage [V]
480V or more
Fuse maximum
allowable rating [A] *
40
70
80
90
110
150
175
200
250
300
CAUTION
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 relay function. Install
an external thermal relay to each motor.
When the 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.
A special motor cannot be protected by the electronic thermal relay function. Use a external thermal relay.
Electronic thermal relay does not function when 5 % or less of inverter rated current is set to electronic thermal relay setting.
Operation region
Region on the right of
characteristic curve
Non-operation region
Region on the left of
characteristic curve
Characteristic when
electronic thermal relay
function for motor protection
is turned OFF (Pr. 9 = 0 (A))
Region for
transistor
protection
Inverter output current (%)
(% to the rated input current)
Pr. 9 = 100 % setting of
inverter rating
*2
Pr. 9 = 50 % setting of
inverter rating
*1, 2
or more
*3
Operation time [s]
Operation time [min]
[s] unit display in this region
[min] unit display
in this region
or more
*3
