Selection and protection of a motor Parameter
6 - 80
6.8 Selection and protection of a motor
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.
ī
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.
ī
The above parameters can be set when Pr. 160 "User group read selection" = 0.
ī
When parameter is read using the FR-PU04, a parameter name different from an actual parameter
is displayed.
Purpose Parameters that must be set
Refer to
Section
Motor protection from overheat Electronic thermal O/L relay Pr. 9, Pr. 51 6.8.1
Use the constant torque motor Applied motor Pr. 71, Pr. 450 6.8.2
The motor performance can be maxi-
mized for operation in magnetic flux
vector control method.
Offline auto tuning Pr. 71,
Pr. 80āPr. 84,
Pr. 90āPr. 94,
Pr. 96, Pr. 859
6.8.3
Pr.
No.
Name Initial Value Setting Range Description Parameters referred to
Refer to Sec-
tion
9
Electronic thermal O/L relay
Rated inverter
current
ī
0ā500A Set the rated motor current.
71
72
178ā184
190ā192
Applied motor
PWM frequency
selection
Input terminal function
selection
Output terminal
function selection
6.8.2
6.15.1
6.10.1
6.10.5
51
Second electronic
thermal O/L relay
ī ī
9999
0ā500A
Made valid when the RT signal is on.
Set the rated motor current.
9999
Second electronic thermal O/L relay
invalid
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