all 3 terminals..this is a 3 phase system
ill check for acid but what causes all 3 to ground out?
this is a walkin refer with 3 evaporators..customer says
last evaporator never really put out cold air..
thoughts?
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all 3 terminals..this is a 3 phase system
ill check for acid but what causes all 3 to ground out?
this is a walkin refer with 3 evaporators..customer says
last evaporator never really put out cold air..
thoughts?
Single phrasing can. Recommend a phase monitor and of course check for any problems once you have it running again.
Attachment 311651
Obviously not your compressor but just a stock photo of a 3 phase stator. Notice how everything touches? A little fire on one winding will burn across everything and can short out the whole fam damly.
O-tay..thanks..im not familure with a phase monitor..how do they work?
How big is the motor? Any multi-hp will have a winding resistance that's close to "zero" as far as you can read on a normal multimeter.Quote:
Originally Posted by primmers
Motors are either wound as delta(Δ)or wye(Y). In Delta wound, all three corners are connected to outside. In "Y" the three ends are, but the center knot is not.
As you can visualize, if any part of the winding touches the core, it will look like all 3 points are shorted, but in reality, you probably have a spot or two inside that shorted to the core.
More difficult ones are partial shorts that cause some turns to be skipped, therefore cause abnormal phase imbalance (i.e. coil #1 with 20% of turns bypassed due to a short will have overcurrent)
It's an electronic device that monitors incoming voltages and watches for proper phasing. If voltage increases/drops or if it sees a voltage imbalance, it opens a set of contacts and shuts the machine down. Usually there is a built in time delay that is also configurable. If for some reason there is a power event where it has single phased, the monitor will hold it out until it sees good power again or you come reset it. The ones we use have a line/load feature where it watches the load side also.Quote:
Originally Posted by primmers
I think a phase monitor should be installed on all three phase motors, that would cause less failure in the field. Any thoughts?
this system has one...and no acid in the sytem...BUT when i was packing up my tools one of the maintenance guys said he replaced a contactor some time ago, said one wire was burnt..............
sounds like a wire was not tight on old contactor ... thats probly what began to fry the field wiresQuote:
Originally Posted by primmers
thats what im thinking too^^^ glad the guy finally said something..