Answer / madhu

This kind of starter is required when the motor is required
to run in both forward as well as reverse directions
according to the application.

Power circuit: There is one more power contactor connected
across the power contactor in the power circuit with two of
the phases interchanged to achieve reversal of rotation. The
two contactors are mechanically interlocked to ensure that
both of them do not operate simultaneously. The shorting of
two different phases is avoided through this arrangement.
•

Control circuit: The control circuit obviously consists of
two start push buttons, one for ‘FORWARD START’ and another
for ‘REVERSE START’. Each of them controls the supply to the
respective contactor coils responsible for the supply to the
motor in forward and reverse modes. The stop command is
common for both modes since it is independent of type of
operation. The NC contact of forward contactor is connected
in series with reverse contactor coil and that of reverse
contactor is connected in series with forward contactor
coil. This is the electrical interlock, which ensures that
only one contactor will pick up at a time avoiding any
mal-operation and consequent damage to the feeder and
problems to the dependant processes.
•
Indication circuit: One more Red LED is required to indicate
the ‘Reverse ON’ mode.
One NO contact of the reverse contactor is connected in
series with it.

Answer / madhu

RDOL IS NOTHING BUT REVERSIBLE DIRECT ON LINE STARTER.

This kind of starter is required when the motor is required
to run in both forward as well as reverse directions
according to the application.

Power circuit: There is one more power contactor connected
across the power contactor in the power circuit with two of
the phases interchanged to achieve reversal of rotation. The
two contactors are mechanically interlocked to ensure that
both of them do not operate simultaneously. The shorting of
two different phases is avoided through this arrangement.

Control circuit: The control circuit obviously consists of
two start push buttons, one for ‘FORWARD START’ and another
for ‘REVERSE START’. Each of them controls the supply to the
respective contactor coils responsible for the supply to the
motor in forward and reverse modes. The stop command is
common for both modes since it is independent of type of
operation. The NC contact of forward contactor is connected
in series with reverse contactor coil and that of reverse
contactor is connected in series with forward contactor
coil. This is the electrical interlock, which ensures that
only one contactor will pick up at a time avoiding any
mal-operation and consequent damage to the feeder and
problems to the dependant processes.
•
Indication circuit: One more Red LED is required to indicate
the ‘Reverse ON’ mode.
One NO contact of the reverse contactor is connected in
series with it.

where to use CT and PT?

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