Ammeter Location for Star-Delta Starter Circuit

I'm following up on my earlier questions, with the caveat that frugal, commercial conditions differ from academic or forensic conditions. In other words, adding metrology when one is unsure what will or should happen is vastly different from doing so when one knows how a system should work.

What will the existing ammeter location inform an operator as they cycle through the normal operations of starting and running operations?

I understand with the present location , can see only the current through the windings (both in Star and delta) and not the line current.

Will the existing ammeter location provide any useful information during an anticipated fault condition for either starting or running operation?

Yes, it can as the ammeter can see the current through the windings during starting (star) and running (delta)

Will moving the ammeter to the proposed location improve or obfuscate operational and fault conditions for an operator?

May be no, as the operator can see the line current (current consumption) but not the actual current when running (delta)

Will adding a second ammeter to the proposed location, with potentially differing levels, clarify or confuse an operator during running, starting, and/or fault conditions?

Yes, it can

The area marked in red would be the best position for the 3 phase ammeters using CTs. The present position of the ammeter and CT on one phase only does not give a full indication of the motor current per phase.

When single ammeter on one phase and three phase ammeter on all three phases would be deemed appropriate? (apart from commercial reasons)

It is of little practical use. A 3 phase motor protection relay would be your best investment for a large expensive motor, so you might analyze unbalance currents and possible rotor heating. A display instrument will not have the precision needed to do a thorough analysis.

A star delta starter is rarely needed, and in itself provides usually unnecessary stress on motor windings. Much better to model your power system and find out if the reduced voltage starter is needed at all. The starter itself reduces the reliability of the process by usually unnecessarily introducing more points of failure in your manufacturing system.

I'm not an electrical guy (I'm instrumentation-mostly electronics) but I have worked on motor controls out of necessity.

In all of the motor controls I've worked on, the ammeter was connected in the location of your red box, between the contactor and the breaker. When I asked one of my electrician friends, he answered, "The ammeter is supposed to monitor the current load on the supply. Also, the meter will show you if the current is close to or exceeding the breaker setting. If the motor is operating close to or occasionally exceeding the breaker setting, you can bet that the breaker will soon trip off."

I bow to the knowledge of people who actually trained on these things. (",)

regards,

Vulcan