Technical information

1.3.1.4 Controller

100-C UL 500 NEMA

The definition of controller is somewhat generic because this term refers to any

components that enable a load to be commanded: for example even a motor

protector when manually operated is considered to be a controller.

In this analysis the magnetic controllers, or contactors are taken as a reference.

In the case of a direct start the contactor is easily chosen in the catalogue while

respecting a small number of obviously rules:

–having a rated voltage that is not smaller than the one of the circuit;

–that the size (in amperes) is not smaller than the sum of the scaling of the

controlled loads, in the simplest case of direct starting of a single motor it can

be scaled on the power of the motor,in hp;

–be approved for the type of load controlled.

ery motor m ust be controlled b y a dedicated contactor. An exception is

admitted in the USA for Industrial Machinery in the case of a single contactor

that has to co-ordinate the functioning of more than one load (mixed, not

necessarily motors): the current is scaled and calculated as the sum of the rated

currents of all the loads.

EXAMPLE

The contactor must be adapted for a

voltage of 480V and must be suitably

scaled to the motor.

In the case of direct starts the

contactor can be scaled on the basis of

the power: the contactor must

therefore have a size of at least 5 hp.

The suitable IEC/UL/CSA component is

a 100-C16x10 contactor with rating

equal to 5 hp and a auxiliary NO

contact.

In a NEMA starter a 5 hp 500-BOx930

and with a NO auxiliary contact is

used.

BRANCH CIRCUIT