SEL-701-1 Monitor
Date Code 20011009
Settings Calculation
Basic Motor Protection
3.8
Basic Motor Protection
Thermal Model Element
The SEL-701-1 Monitor includes a thermal element that provides integrated
protection for all of the following motor operating conditions:
Locked Rotor Starts.
Running Overload.
Unbalance Current/Negative-Sequence Current Heating.
Repeated or Frequent Starting.
The Setting Method setting selects the thermal element algorithm that will be used
in the SEL-701-1 Monitor. The Setting Method setting offers four options: Rating,
Generic, User, and OFF.
Rating Setting Method.
When selected, the monitor configures a thermal curve
based on the motor Full Load Amps, Service Factor, Locked Rotor
Amps, Hot and Cold Locked Rotor Time, and Locked Rotor Trip Time
Dial settings.
Generic Setting Method.
When selected, the monitor offers 45 standard motor
thermal limit curves which you can select by curve number.
User Setting Method.
When selected, the monitor allows you to build a
customized thermal limit curve by directly entering from 5 to 25 time-
current points based on your motor’s published thermal limit curve.
All three thermal element setting methods can provide outstanding motor
protection. In each case the monitor operates a thermal model with a trip value defined
by the monitor settings and a present heat estimate that varies with time and changing
motor current. The monitor expresses the present motor thermal estimate as a
% Thermal Capacity. When the % Thermal Capacity reaches 100%, the monitor trips.
You can see the present % Thermal Capacity value using the monitor front panel Meter
Values\Thermal & RTD Data function or the serial port
METER T
command.
If the Thermal Model is turned off (SETMETH= OFF), the thermal model is
disabled, the output of the thermal model is blocked, and the monitor reports the
% Thermal Capacity as either 0 or 999.9% as noted in
. It is recommended that you reset Load Profile, Motor Statistic, Motor
Start Trend data and Learned Motor Parameters when the Thermal Model is turned
back on. See
Section 4: Front-Panel Operation
and
for the reset procedure.
Содержание SEL-701-1
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