Hellow Softstarter,

The device provides remote controlled tripping. It includes an intermittent rated solenoid with a tripping plunger and cutoff switch mounted on a plug in module. On AC rated shunt trips required for use with ground fault protection devices, most solenoids are suitable for operation at 55 percent rated voltage.

Field testing is facilitated by push to trip button on each service circuit breaker. The button checks the tripping function and should be used during scheduled maintenance to periodically excerise the operating mechanism.

For more info you can contact Westinghouse control department.....

Kind Regards,
motorhead1

Sounds like motorhead1 covered it.  I'll just add some ramblings.

In the applications I have seen the shunt trip provides the capability for remote tripping of molded case circuit breaker, which would not otherwise be remotely trippable.  (you don't need a shunt trip for a metal-frame circuit breaker which already has an electrical trip coil).

In some obscure nuclear applications a similar function is played by an undervoltage trip device wired to a control signal. That provides a failsafe function which trips the breaker upon losss of power.

An important feature for shunt trip is the cutoff switch that motorhead mentioned to remove power after the breaker trips since shunt trip coil will likely not be rated for continuous energization. This can be accomplished by wiring the shunt trip coil in series with a breaker "a" auxiliary contact.

Hi MotorHead1 & Electripete..

Thanks for ur materials..

Softstarter

Suggestion: Visit
http://www.airpaxppp.com/pppsite/config.html
http://www.sea.siemens.com/power/product/speedfax/section8/p323.pdf
http://www.airpaxppp.com/pppsite/applic.html
etc. for more info
The shunt trip can be applied to circuit breakers, disconnect switches, and various latched devices where the shunt trip coil released the latch (e.g. relays, locks, etc.).

As I mentioned, shunt trip is an energize-to-trip device in my experience.

Does anyone know where the terminology "shunt trip" came from?  Usually the term "shunt" implies parallel wiring.  How does that apply to a shunt trip device?

Hi softstarter,

Given you choose the handle "softstarter" I am going to assume that your question pertains to shunt trips with softstarters which uses that term slightly differently than any other industry.

The solid-state conductors (SCR's) in a softstarter most commonly fail in a closed position, i.e. Shorted. Once that happen the softstarterdoes not have a way to stop current flow in that phase. Typically shorted SCR's occur in two  phases. So the motor can no longer be controlled by the softstarter.
Most softstarter makers put in a circuit that upon detecting the shorted SCR condition energises a small relay that can be used to power the shunt trip or energise the coil on a contactor just up-stream of the softstarter.

This usage of the term softstarter only applies to motor control using softstarters.

To electricpete,

The way I get it the term "shunt" is derived from the fact that the shunt trip overrides any other command being imposed.