Electronic Overcurrent Protection (Pr. 9) - Mitsubishi FR-F500 Instruction Manual

Note: 1. In S-shaped acceleration/deceleration pattern A (refer to page 79), the set time is a period
required to reach the base frequency set in Pr. 3.
Acceleration/deceleration time calculation expression when the set frequency is the base
frequency or higher
4 T
t =
×
2
9 (Pr.3)
T: Acceleration/deceleration time setting(s)
f: Set frequency (Hz)
Guideline for acceleration/deceleration time at the base frequency of 60Hz (0Hz to set
frequency)
Frequency setting (Hz)
Acceleration/
decelerationtime (s)
2. If the Pr. 20 setting is changed, the settings of calibration functions Pr. 903 and Pr. 905
(frequency setting signal gains) remain unchanged. To adjust the gains, adjust calibration
functions Pr. 903 and Pr. 905.
3. When the setting of Pr. 7, Pr. 8, Pr. 44 or Pr. 45 is "0", the acceleration/deceleration time is 0.04
seconds.
4. When the RT signal is on, the other second functions such as second torque boost are also
selected.
5. If the shortest acceleration/deceleration time is set, the actual motor acceleration/deceleration
time cannot be made shorter than the shortest acceleration/deceleration time determined by the
mechanical system's J (inertia moment) and motor torque.

4.2.6 Electronic overcurrent protection (Pr. 9)

Pr. 9 "electronic thermal O/L relay"
Set the current of the electronic overcurrent protection to protect the motor from overheat. This feature
provides the optimum protective characteristics, including reduced motor cooling capability, at low speed.
Parameter
Factory Setting
Number
9 Rated output current
<Setting>
Set the rated current [A] of the motor.
(Normally set the rated current value at 50Hz if the motor has both 50Hz and 60Hz rated current.)
Setting of "0" makes the electronic overcurrent protection (motor protective function) invalid. (The inverter's
output transistor protective function is valid.)
When using a Mitsubishi constant-torque motor, first set "1" in Pr. 71 to choose the 100% continuous torque
characteristic in the low-speed range. Then, set the rated motor current in Pr. 9.
Note: 1. When two or more motors are connected to the inverter, they cannot be protected by the
electronic overcurrent protection. Install an external thermal relay to each motor.
2. When a difference between the inverter and motor capacities is large and the setting is small, the
protective characteristics of the electronic overcurrent protection will be deteriorated. In this case,
use an external thermal relay.
3. A special motor cannot be protected by the electronic overcurrent protection. Use an external
thermal relay.
5
2
× f + 9 T
60
5
15 15
Setting Range
0 to 500A
120
5 12
35
Related parameter
Pr. 71 "applied motor"
71
PARAMETERS
4