208 3 phase 1.5 h.p. motor rotational change
208 3 phase 1.5 h.p. motor rotational change
(OP)
Ok guys the equipment is a 155 ton split chiller.
as described 3 phase 208 voltage 1.5 H.P. motor ,
some of the fans will change rotation or rather run backwards at start up and then the next startup will run in the proper rotation,
Notes current checks are ok so far. motor ohms out ok .
voltsge checks good never had this type of problem, am i lossing my mind are is it so simple i cant see the forest for the trees.
Thanks Sambullion
as described 3 phase 208 voltage 1.5 H.P. motor ,
some of the fans will change rotation or rather run backwards at start up and then the next startup will run in the proper rotation,
Notes current checks are ok so far. motor ohms out ok .
voltsge checks good never had this type of problem, am i lossing my mind are is it so simple i cant see the forest for the trees.
Thanks Sambullion





RE: 208 3 phase 1.5 h.p. motor rotational change
Bill
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"Why not the best?"
Jimmy Carter
RE: 208 3 phase 1.5 h.p. motor rotational change
air currents vs electric currents ?
Seriously though, wouldn't single phasing act as a brake on an idle 3 phase motor and prevent the driven fan from spinning at all due to air currents ?
RE: 208 3 phase 1.5 h.p. motor rotational change
I have seen this happen. There are always exceptions but although single phasing developes quite a bit of force, the force is at right angles to the direction needed to produce torque. Because of the lagging phase angle of the rotor current producing the force, any rotation will allow the force developed by the single phase condition to develop torque. It is common to see cooling fans on transformers turning gently in the breeze. If single phase power is applied, the fans will accelerate in the same direction that they were being turned by the breeze.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: 208 3 phase 1.5 h.p. motor rotational change
I do suspect that the fans counter rotation prior to, being energised is casuing a problem , This circut has a total of 5 fans, the fans spin in counter rotation due to the first stage of the circut being placed in operation...
Thhanks again , Sambullion
RE: 208 3 phase 1.5 h.p. motor rotational change
If you stop the fan and let it re-start does it still go backwards.
You need a phase rotation indicator to help you troubleshoot this I think.
Good Luck, keep us posted.
Roy
RE: 208 3 phase 1.5 h.p. motor rotational change
I've even built 6 channel head pressure fan controllers from scratch to do exactly this and never seen that occur with 3 phase fans.
Keith Cress
kcress - http://www.flaminsystems.com
RE: 208 3 phase 1.5 h.p. motor rotational change
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: 208 3 phase 1.5 h.p. motor rotational change
THANK YOU ,
makes me wish i would have brought home the schematic where i could have been more concise in my description of the circut, and the sequence of operation,.
Though i am convinced i simply have a bad motor i suppose the thing that baffle me most is the interment behaviour,
I suspect i will find a fuse blown, when i go back to it on Monday...
But i will post again when i do find the Gremlin that has caused me to scratch my old bald head....
Best Regards
Sambullion
RE: 208 3 phase 1.5 h.p. motor rotational change
Another example of why fuses are lousy for quality motor protection.
Keith Cress
kcress - http://www.flaminsystems.com
RE: 208 3 phase 1.5 h.p. motor rotational change
Best regards,
Mark Empson
L M Photonics Ltd
RE: 208 3 phase 1.5 h.p. motor rotational change
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: 208 3 phase 1.5 h.p. motor rotational change
RE: 208 3 phase 1.5 h.p. motor rotational change
Thought you might like to know wher i got to today ,
Well lets start this way i did not win....
But for those of you who would like to know a tad bit more.
The fuse was blowed as expected so i ordered me a mtr. they are rather proud of them.. So i install a new fuse and begin my checks , I must degress a bit this circut for whatever reason which consist of 2 fan mtr. sharing the same contactor,,, so which mtr. is failing shouldnt be a problem ,
Pull all leads from contactor for both mtrs.
All legs ohm out ok to grd. all legs give consistent ohm values and are similar very close , using a digital fluke meter.,
What to do right , Hook every thing back up and lets get some current readings
all legs within 1/10 of a amp of each other. Remember i got got a bunch off these fans and gee you would think this would be straight forward. NOPE NOT TODAY...
So while i have my men cleaning the coils and regular PM,
And i still know i got a bad mtr. just dont know which one,
So i check the circut wiring look at every inch looks good,
Physcialy look at mtr terminations still ok
OHm out at the terminial at the mtr again ok.
Well the motor want be here till tuesday ,so what do i do
I move the leads for one of the mtrs to another contactor and hopefully i will have a blown fuse in the morning..
Yep i turned the chiller back on both circuts and well if it holds overnight them boys will have icicles hanging off of ther toes....
RE: 208 3 phase 1.5 h.p. motor rotational change
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: 208 3 phase 1.5 h.p. motor rotational change
I know its a waste of money but i am going to send this mtr to a rewind shop , I JUST GOT TO KNOW what in the heck going on in i've seen all kinds of things that have baffled me over the years but this takes the cake,
And fellers thank you one and all
Best Regards
Greg
RE: 208 3 phase 1.5 h.p. motor rotational change
RE: 208 3 phase 1.5 h.p. motor rotational change
I can't say that I have experienced this. From my experience, in most cases with low slip induction motors, the start current is the same, but because the starting slip is higher, the start time is longer and this will operate protection etc.
Best regards,
Mark Empson
L M Photonics Ltd
RE: 208 3 phase 1.5 h.p. motor rotational change