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Explanation of functions (parameters)
2
FUNCTIONS
2.3.6
Selection and protection of a motor (Pr. 9 , Pr. 71 , H7 )
• The parameter number in parentheses is the one for use with the parameter unit (FR-PU04).
<Setting>
•Refer to the following list and set Pr. 71 according to the motor used.
Setting "100 or 101" changes thermal characteristic of the electronic thermal relay function
to thermal characteristics of a Mitsubishi constant-torque motor when the RT signal is ON.
•Set the rated current [A] of the motor in Pr. 9. (Normally set the rated current at 50Hz.)
•Setting "0" in Pr. 9 disables electronic thermal relay function (motor protective
function). (The protective function of the inverter is activated.)
•When setting second electronic thermal relay function, set the motor rated current
value in the additional parameter H7. The second electronic thermal relay function is
valid when the RT signal is on. (When the RT signal is on, other second functions
(Pr.44 to Pr.47) are also selected.)
Set the motor used and protect the motor from overheat.
This feature provides the optimum protective characteristics, including reduced
motor cooling capability, at low speed.
POINT
•When using the Mitsubishi constant-torque motor
Set "1" in Pr. 71 for V/F control or automatic torque boost control.
The electronic thermal relay function is set to the thermal characteristic of the
constant-torque motor.
•When you selected the Mitsubishi constant-torque motor, the values of the following
parameters are automatically changed. (only when the setting values of those
parameters are at factory setting)
Pr. 0 "torque boost", Pr. 12 "DC injection brake voltage"
Para
meter
Name
Factory
Setting
Setting
Range
Remarks
9
Electronic thermal
O/L relay
Rated output
current
0 to 50A
71 Applied motor 0
0, 1,
100, 101
Setting is
enabled
when
Pr. 30 = "1"
H7
(559)
Second electronic
thermal O/L relay
- - -
0 to 50A,
- - -
- - -: Without second electronic
thermal relay function
Pr. 71 Setting Thermal Characteristic of the ElectronicThermal Relay Function
0, 100 Thermal characteristics of a standard motor
1, 101
Thermal characteristics of a Mitsubishi constant-torque motor
(This provides a 100% continuous torque characteristic in the low-speed region.)
CAUTION
•When two or more motors are connected to the inverter, they cannot be
protected by the electronic thermal relay function. Install an external thermal
relay to each motor.
•When a difference between the inverter and motor capacities is large and the
setting becomes less than half amount of the inverter rated current, 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 an external thermal relay.