Selection And Protection Of A Motor; Motor Overheat Protection (Electronic Thermal O/L Relay) (Pr. 9, Pr. 51) - Mitsubishi Electric FR-E700 Series Instruction Manual

Selection and protection of a motor

6.8 Selection and protection of a motor
Purpose
Motor protection from overheat
Use the constant torque motor
The motor performance can be maxi-
mized for operation in magnetic flux
vector control method.
6.8.1

Motor overheat protection (Electronic thermal O/L relay) (Pr. 9, Pr. 51)

The FR-E700SC EC frequency inverters have an internal electronic motor protection function that
monitors the motor frequency and motor current. Overload conditions are identified and the motor
protection function is triggered on the basis of these two factors, in combination with the rated motor
current. The electronic motor protection function is primarily for protection against overheating at in-
termediate speeds and high motor torques. The reduced cooling performance of the motor fan under
these conditions is also taken into account.
Pr.
Name
No.
9
Electronic thermal O/L relay
Second electronic
51
thermal O/L relay
The initial value of the FR-E720S-050SC or less and FR-E740-026SC or less is set to 85% of the
rated inverter current.
The above parameters can be set when Pr. 160 "User group read selection" = 0.
When parameter is read using the FR-PU04, a parameter name different from an actual parameter
is displayed.
6 - 80
Parameters that must be set
Electronic thermal O/L relay
Applied motor
Offline auto tuning
Initial Value Setting Range
Rated inverter
0–500A
current
0–500A
9999
9999
Description
Set the rated motor current.
Made valid when the RT signal is on.
Set the rated motor current.
Second electronic thermal O/L relay
invalid
Parameter
Refer to
Section
Pr. 9, Pr. 51 6.8.1
Pr. 71, Pr. 450 6.8.2
Pr. 71, 6.8.3
Pr. 80–Pr. 84,
Pr. 90–Pr. 94,
Pr. 96, Pr. 859
Parameters referred to
71 Applied motor
72 PWM frequency
selection
178–184 Input terminal function
selection
190–192 Output terminal
function selection
Refer to Sec-
tion
6.8.2
6.15.1
6.10.1
6.10.5