induction motor type of connection
induction motor type of connection
(OP)
dear every body
regards
suppose two induction motors both(22kw) , one have star connection at 380 vac , and the other have delta connection at 380 vac .
the question is which one can consume high current at start up at same mechanical load , or what is the expected results
thanks for reply
regards
suppose two induction motors both(22kw) , one have star connection at 380 vac , and the other have delta connection at 380 vac .
the question is which one can consume high current at start up at same mechanical load , or what is the expected results
thanks for reply





RE: induction motor type of connection
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RE: induction motor type of connection
thanks for your reply
the two motors in my question, one is designed to be connected in star at 380VAC-60 HZ
and the other motor is designed to be connected in delta at 380VAC -60 HZ
my question is , at same mechanical load , which motor will consume high current in start up
in other words , are there any relation between the type of connection of induction motors and the starting up
current at same conditions.
thanks,,
RE: induction motor type of connection
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: induction motor type of connection
Differences may occur only if the selected winding has a different harmonic content in "wye" and "delta".
Zlatkodo
RE: induction motor type of connection
In the case of asymmetrical three-phase windings, currents in delta connection are much higher (due to circulatory currents) and this is why the "wye-connection" should be preferred.
Zlatkodo
RE: induction motor type of connection
The potentials applied to the windings of a delta-connected machine are defined by the supply characteristics. In a star-connected machine the star point is an internal connection and is not connected to system neutral; the potential applied to each winding of a star-connected machine is therefore not solely defined by the supply but also by the impedances of the interacting magnetic circuits of the stator windings and the rotor. I expect that the neutral potential will move around a fair bit while the stator magnetic field reaches a stable state.
In both cases the point on the voltage wave at which the supply was energised will have an effect on the behaviour at initial switch on, and there will be saturation effects due to transient DC components. It seems fairly likely that there will be measurable differences in behaviour between a star connection and a delta connection, although whether they are of any practical significance is an entirely different question.
There are better analytical minds than mine who might care to model this; magnetic circuits on the edge of saturation or possibly in saturation are one step too far for my Sunday evening.
RE: induction motor type of connection
It can be proven correct (transient or steady state) using Laplace analysis under assumption of linear behavior
For real motors with non-linear behavior during start, it's an unknown to me.
Was discussed a little here:
http://www.eng-tips.com/viewthread.cfm?qid=251952
On the original question, I agree with other posters fwiw... If there is any difference attributable to connection, it would be related to dc and harmonic components. If the interest of original question is simply the fundamental steady locked rotor currrent (excluding dc), these differences wouldn't matter.
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(2B)+(2B)' ?
RE: induction motor type of connection
Aletric, are you asking this because of a specific problem you are having, such as a breaker tripping on startup?
"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: induction motor type of connection
Yes, it is the non-linear behaviour which I was thinking of when the winding see the initial DC offset from switching. I am sure it can be modelled, but only with a fairly sophisticated model of the magnetic circuits. I have so far drawn a blank in my brief attempt to find any detailed investigation of what happens, perhaps because it is of little interest other than purely academic curiousity.
RE: induction motor type of connection
thread237-285699: Simulating motor w/ non-simult transition of breaker contacts
If we consider only the magnetizing flux linkage (which must sum to zero among three phases), then the instantaneous neutral voltage (including during transient) would be the average of the three phase voltages (using any voltage refernece for all 4 measurements... take your pick).
But the leakage flux linkage does not have the same requirement (sum to zero among three phases), so certainly seems to introduce potential for the neutral voltage to vary if the leakage reactance behaves non-linearly.
I have gone some distance toward trying to simulate this in the past, but never completed. It's not as easy as you'd think but I'm sure it can be done.
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(2B)+(2B)' ?