3 phase problem - need help please

[farmshop]

Square d makes a mechanical starter that is push button with bimetallic overload protection. You could get rid of the transformer and simplify the wiring

[Willie B]

I'll yield to progress. A motor logic control will save a motor, while a solder pot control shuts it off just after it burns up.

Three phase motors are finicky. They want balanced voltage from all three supply wires. A common motor failure is to lose through a bad connection, burned contact in the motor control, or power company losing a leg, current rises in the now single phase system. Square D Motor Logic controls also sense balance of current in all phases.

I've never seen a bimetallic control in a Square D motor control. I have seen plenty of solder pot controls.

[danielplace]

I'll yield to progress. A motor logic control will save a motor, while a solder pot control shuts it off just after it burns up.

Three phase motors are finicky. They want balanced voltage from all three supply wires. A common motor failure is to lose through a bad connection, burned contact in the motor control, or power company losing a leg, current rises in the now single phase system. Square D Motor Logic controls also sense balance of current in all phases.

I've never seen a bimetallic control in a Square D motor control. I have seen plenty of solder pot controls.

Most Square D standard motor starters are basically bimetal just done a little differently. They don't use traditional heaters but rathe what they call thermal units. It is metal heating and the expansion used to release the overload. The overload reset ratchets the overload catchs on small toothed gears on the thermal units to hold it. The axles for those gears are set in copper with enough friction until it heats up, expands and allows the gears axle to rotate dropping out the overload reset levers shutting down the starter. If the thermal units are sized properly for the load they offer a fair amount of protection.
If you are running 3 phase motors that aren't on equipment you use personally then they must have phase monitors or your asking for a expensive repair one day.

[Virgil5]

Some days I wonder how we built and kept the world running till all these whoopie wizbang solid state devices came along.

Then I remember, Lincoln started it with welders with a phone jack that could call home and get deloused at 110 baud. Watched a young fellow with a laptop plugged into a cooler case a while back, case wasn't cooling, laptop was full of green bars and red bars on the screen, and the store owner was pissed hearing the whole case probably needed to be replaced so that one could go back for reconditioning.
Probably a global warming thing.

[Willie B]

Square D pre Motor Logic were the more common solder pot units. A double ended shaft with cog wheels at each end. One cog wheel is in a solder pot. The wheel on the other end holds a ratchet dog. The solder pot is surrounded by a heating element. When current rises too high, the solder melts. This allows it to rotate, The dog slips off the ratchet.

It is a good, time proven system. Its shortcoming is that it doesn't react quickly enough in some applications, and it doesn't react to imbalance in three phase motors. Phase imbalance is often easily fixed. Undetected, it results in motor failure.

[Virgil5]

So was Allen Bradley, Cutler Hammer, GE. Westinghouse and Colt. They all worked fine and are still working in many applications not corrupted by clever college boys with computers.

[MinnesotaDave]

Success

The new fuses came, still blew them instantly.

Decided to follow you guys advice and go to a full voltage magnet.

Stole this one from the shaper to test the theory.
Bypassed the transformer.
Fired right up.

[Country Metals]

Awesome!

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[MinnesotaDave]

Awesome!

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I thought so too

The help from all the guys here did the trick and now I've learned a bunch about 3 phase and magnetic starters in general.