Technical information

Table Of Contents

6 – APPLICATIONS

Line Connected Motor

6.1 Application Consideration between Line Connected and Inside Delta Connected Soft Starter

There are differences between a line connected soft starter as shown in Figure 10 and the inside delta connected soft starter as shown

in Figure 11 that need to be understood.

By observation of Figure 11, access to all six stator-winding terminals is required for an inside delta application. For a 12-lead

motor, all 12 stator terminals must be accessible. In the line connected soft starter of Figure 10, access to only three leads of the

stator windings of the motor is required.

One failed SCR on any phase of the inside delta soft starter results in a single-phase condition. A shunt trip circuit breaker is

recommended to protect the motor in this case. A programmable relay can be configured as a shunt trip relay and can be used to trip

the breaker. When certain faults occur, the shunt trip relay energizes. Refer to Appendix B – Fault Codes, for those faults that cause

a shunt trip.

The SCR control for an inside delta application is different than the SCR control for a standard soft starter. The Starter Type

parameter needs to be properly set so that the SCRs are gated correctly.

If a circuit breaker is the only means to disconnect the soft starter and motor from the line, then one leg of the motor leads in the

inside delta soft starter is always electrically live when the circuit breaker is closed. This requires caution to ensure these leads of the

motor are not exposed to personnel.

6.1.1 Line Connected Soft Starter

In Figure 10, the power poles of the soft starter are connected in series with the line. The starter draws line current (L1, L2, L3).

Figure 10 – Typical Motor Connection

Motor