Technical information

The choice of the contactors occurs as in a normal direct starting supposing that
each of them commands a dummy motor with current, at fully capacity and with
locked rotor,equal to those calculated.
In the catalogue, the catalog numbers are specified by power so it is necessary to
switch the calculated current values into power output values (hp).
As far as the FLA is concerned these are identical to what is obtained in example
2, but in this case the line and delta contactors must be sized also on the basis of
the LRA of the dummy motor.It should be kept in mind that the contactors still
equal LRA = 6 x FLA. It’s obtained
The line contactor satisfies the sizing conditions also in this case but the delta
contactor is smaller than the LRA.
A correct choice requires a contactor with
LRA contactor >= LRA motor = 140 A
Therefore
6 x FLA contactor >= 140 A
x FLA contactor >= 140/6 23.3 A
From the FLA table it can be deduced that the contactor that fully meets this
condition must have a power of 20 hp at 480 V (FLA equal to 27 A): from the
catalogue the 100-C30 is chosen.
BRANCH CIRCUIT
58
Contactor code LRA FLA
1M 0.33 x 243 A z 80 A0.577 x 27 A z 16 A
2M 0.577 x 243 A z 140 A0.577 x 27 A z 16 A
S00.33 x 27 A z 9 A
Contactor code Dummy motor
Contactor
ex. 2
FLA [A] Code FLA [A]
LRA [A] Power [hp] LRA [A]
1M
16 100-C23 21
80 15 hp 126
2M
16 100-C23 21
140 15 hp 126
Contactor code Dummy motor
Contactor
ex. 2
FLA [A] Code FLA [A]
LRA [A] Power [hp] LRA [A]
2M
16 100-C30 27
140 20 hp 162
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