newbie question - y and delta connected motor

hi, i'm newly assigned to our plant's electrical engineering group. One of our motors (15HP, 18.5amps, 3P-440v 1140 RPM Y-connected)broke down
and was contracted out for rewinding. upon delivery to our site, the motor current reading on y-connection was only about 2.3Amps/line. However, when the supplier engineer reconnected the motor into Delta, it's current reading was at 10.6A/line. Though, personnally, I don't want to accept the motor since they should have doen it according to original design, my boss wants me to prepare a technical memo stating the disadvantage and advantages of such connections.
Could anyone kindly help/enlighten me please to support our position against the supplier since they sent a memo guaranteeing the performance of the rewound motor. the application BTW is on Oven blower fan.
thanks a lot
/louie
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
     snipped-for-privacy@jpopmail.com (louie) writes:

I think it's rather unusual for a motor of that size to be Y (or star as we call it). Typically, it would be started in Y configuration and switched to delta after it's had time to pick up a bit of speed. Are you sure it was originally connected as Y ?

Presumably they had the rating plate on the motor? Have they updated that to a new spec?
--
Andrew Gabriel

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) wrote in message (louie) writes:

the said motor is used on our lithography oven blower fan. per our electricians, it's connection is star. What we want the supplier to do is to rewound it to what is the original spec and not as delta connection. Though they give us guarantee on its performance even when delta connected, instincts tell me that somehow we could encounter trouble when it is installed in the line. Breakdown of it will surely cost us money on material and manhours. In these regard, could you give the disadvantage if we use the delta connection as against the star(y) connection.
thanks in advance
louie
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
dated 4 Sep 2004 20:45:42 -0700,

Delta is better.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
First, I can't believe that you rewound a $750 motor, unless this is a special frame.
Is this a 6/9/12 lead motor? What is the full name plate information? How do you know that this motor was originally wye connected?
In the wye connection you didn't have enough voltage to properly set up the magnetic field. I am guessing that it also did not come up to speed.
On 4 Sep 2004 02:55:24 -0700, snipped-for-privacy@jpopmail.com (louie) wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Earlier posts are all correct. A motor of this size is usually connected in Delta. If connected in star (Y) the torque produced by the motor is much lower. One exception (UK) is motors can be rated for 400 V Delta or 690 Volts Star. Another exception is a motor can be wound for 415 Volts Delta, 230 Volts Star. Check the motor nameplate.
(louie) wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

in
Star.
Uh, wouldn't that be 415 V Star and 230V delta?? The lower voltage is usually the delta connection.
daestrom
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Ooops! Wrong way round. Sunday morning.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I think something is wildly wrong, either with the motor or with your question.
First, whether the motor is delta or wye connected is absolutely irrelevant to everything. A motor may be designed for either connection at any reasonable voltage. I also can not picture a motor shop making a mistake like that. If all the leads are brought out, which is apparently the case, what is the difference between a wye and a delta winding? NONE!
Second, unless you are talking about running the motor with no load, I can't imagine a motor of that spec drawing only 2.8 amps, no matter how it was connected. Certainly NOT while driving a load!!
There appears to be a big piece of the story that is not told here.
I would like the complete nameplate info on this motor. How much current did it draw before it failed?

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I agree that something is missing here, probably due to inexperience. Assuming that you have 6 leads to connect, for your Y connection you probably connected to 1,2 & 3, then tied 4,5 & 6 together right? Now the rewound motor wants a connection of 1 & 6, 2 & 4, 3 & 5 right? It does make a difference as to the connection, depending upon how the motor was originally designed. If in the original design it was connected in Y, and you got full torque and full HP, then that was how it was designed. But after rewinding, if the shop wound it for Delta, then THAT is how it is now ready to operate. Connecting a Delta wound motor in Y will give you 1/3 torque and 1/3 current, so don't do that.
The net result however should be exactly the same as long as you hook it up as it was intended. So technically the motor shop is correct. It makes no difference as long as you get the right results. The only caviat is that Delta connections are much more common, so using Y may lead to this kind of confusion again later. Stick to Delta.
YOU however may be getting sent on a "snipe hunt" by your boss. He probably already knows this, he just wants to see you sweat!
The only other possibility is that it was a 2 speed 1 winding motor and you were connecting only the low speed. Any decent motor shop would have known it though. If it is turning at the correct speed when connected in delta, quit worrying about it.
On Sun, 5 Sep 2004 12:50:19 -0400, "BFoelsch"

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.