Specification

Motor Control Solutions Structure of a Motor Starter in Accordance with UL 508A

Structure of a Motor Starter in Accordance with UL 508A

Feeder Circuits and Branch Circuits

The feeder circuit includes all power conductors and components from the

incoming feeder disconnect to the line side of the last branch short-circuit

protection device (SCPD).

The branch circuit includes all power conductors and components from the load

side of the branch circuit SCPD to the controller load-side connections.

Each branch circuit should be protected by its own disconnect and SCPD.

Table 2 contains a description of the numbered circuit components called out in

Figure 2.

Figure 2 – Feeder Circuit and Branch Circuit

Table 2 – Circuit Components

1 Load—provided in the field 14

Control transformer ground

(for 1000 VA max. control transformer)

2 Field wiring terminals 15

Control circuit devices and wiring—Class 1 circuit—isolated

secondary circuit

3 Alternate field terminals 16 Solenoid or other control device—provided in the field

4 Field wiring 17 Supplementary protection

5 Internal wiring of the power circuit 18 Class 2 transformer

6 Overload relay and heater elements 19 Class 2 circuit

7 Contactor or controller 20 Power transformer fuse—branch circuit protection

8 Starter 21 Power transformer—for motor load and control protector

9 Combination motor controller 22 Control circuit—Class 1 circuit—common control circuit

10 Branch circuit protection 23 Equipment ground and equipment ground terminal

11 Fused disconnect switch or circuit breaker 24 Bonding conductor—bonding jumper

12 Control transformer 25 Grounding electrode conductor terminal

Control transformer fuse or supplementary

protection

26 Grounding electrode conductor—provided in the field