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#165215 06/22/07 11:53 PM
Joined: Mar 2005
Posts: 212
G
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So here's one I should know, but my background is lacking. If I have a 12 lead 3 ph 480v motor and there is one connection diagram for wye start and one for delta run, what piece of info do I need to know which one to use?

Joined: Feb 2003
Posts: 939
F
Member
The wye-delta motors are pretty picky with the system.

It will depending on what HP size and also want to give you a head up that you can't really run the wye not for very long [ useally 30 sec max otherwise it will overheat ] and running will be delta connection unless you go DOL [ Driect on line ] i will post a link so you can see the connections look like

Y-D connection [ both 6 and 12 leads]

so that the idea how it hook up

that pretty typical for Y-D and also have Y-D starter as well

Merci, Marc


Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)

Joined: Sep 2004
Posts: 68
H
Member
Greg,
A specially configured starter is required to start and run a motor in this manner. I believe any twelve lead squirrel cage motor can be operated using the "star-delta" or "wye-delta" method. Three contactors reside in a starter of this type. One of the contactors bridges between 10,11 and 12 during the starting period, which is usually an adjustable time.

Have you considered using either a "soft-start" starter or a variable frequency drive? The prices of these solid state devices have become much more competitive with the star-delta starter in recent years and the wiring is so much simpler--three leads plus ground in and three leads plus ground out to motor. To use the wye-delta starter, all 12 leads must be brought out to the starter from the motor. If the shaft bearings are properly grounded with grounding kits, and the motor is purchased with windings that are suitable for the higher D.C. voltages often present in motors connected to VFD's, the motor will last a long time. A google search for information or a call to a sales rep for motors and starters in your local area will produce a wealth of information on the subject.

Good luck!

homer #165221 06/23/07 10:05 AM
Joined: Mar 2005
Posts: 212
G
Member
The motors in question are fed from a VFD. I assumed in the field that this made a Delta run connection the proper choice and I have time to change it if necessary. Did I get it right?

Joined: Sep 2003
Posts: 650
W
Member
Once you have a VFD in the picture, all bets are off. It is _probably_ the case that you would connect the motor in delta, and use a motor with the same nominal voltage as the supply voltage, but this is not necessarily true.

The 'star' and the 'delta' connection are simply two different ways to drive the motor. In the star connection, the voltage required to properly magnetize the motor is higher, but the current required to run the motor is lower, relative to the delta connection. But either will run the motor just fine if the proper voltage at the proper frequency is supplied.

_Normally_ the way a start/delta system is used, the motor is first started in the star connection. Since the star connection requires higher voltage for normal operation, the motor is effectively being operated at substantially reduced voltage. This will tremendously reduce the available torque from the motor, and can only be used with mechanical loads that don't require much starting torque. But this has the great benefit of reducing the starting current of the motor. Then once the motor has gotten up to speed, it is switched over to delta operation in order to operate efficiently.

But with a VFD, you can adjust the output voltage and frequency in an arbitrary fashion, at least within the limits set by the available voltage and the current handling capacity of the VFD itself. This means, for example, that you could select a voltage and frequency combination that would properly run the motor when star connected. As long as you correctly match the V/Hz ratio set on the drive to the particular motor connection, then the VFD will run the motor properly.

I expect that the motor should be connected Delta at your supply voltage, because this lets the motor get to nominal full speed with full available torque. However if the motor/drive system is intended to operate at other speeds (either only at reduced speed, or at higher than nominal speed), then other connections might be used.

What is the nominal HP rating of the motor?

What is the nominal speed rating of the motor?

What are the voltage ratings of the motor?

What is the nominal HP rating of the drive?

At what speeds will the motor normally be operated?

-Jon

winnie #165225 06/23/07 12:16 PM
Joined: Jun 2007
Posts: 301
J
Member
12 lead motors are becoming more available and some motor manufacturers are selling 12 lead exclusively.
The reason being that twelve lead motors can be used in almost any situation. Soft start's, Drives, wye/delta starting,ect....
Wye/Delta starting is the most common. The only time you have to connect a twelve lead motor in both configs is when a wye/delta contactor config is present.
With across the line starting and drives you always use the RUN Delta connection.
A twelve lead motor cannot operate in the wye config for any application except for starting.
If you apply power to the motor in the wye config, you will produce half the Hp only. The current will look great too. But within a few hours or minutes the motor will let the smoke out.
Always use the delta unless you have the wye/delta config (3)contactor arrangement.

Six lead IEC (metric) motors are sometimes dual voltage rated. Here, the high voltage would be the wye, and the low voltage would be the delta.

JValdes #165229 06/23/07 02:32 PM
Joined: Feb 2003
Posts: 939
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Originally Posted by JValdes
Six lead IEC (metric) motors are sometimes dual voltage rated. Here, the high voltage would be the wye, and the low voltage would be the delta.


JValdes :.. yes this is very common with IEC motors espcally that true in european area they used the 6 lead pretty much of the time but i heard they are starting to switch over to 12 leads as well and some do have 3 leads only as well

Merci, Marc


Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)

Joined: Mar 2005
Posts: 212
G
Member
Thank you all for the info. I will have to do some studying to understand this completely but I'm pretty sure I have this connection done correctly. I'm still not sure how one would hook up the motor BOTH ways. Like I said, I'll have to study.

Joined: Jun 2007
Posts: 301
J
Member
Frenche, The metric motor 6 lead system is on the brink. A six lead motor, "they have finally realized" is not conducive to dual voltage and confusing to some in the industry. What I am seeing is the change to 9 lead for dual voltage and twelve lead for general purpose.
I personaly prefer 12 lead. It works in most every application and is less confusing.
However, many people are intimidated by the number of leads, as you can see by the original poster to this thread. I made more service calls when these 12 lead motors started to appear in the US. Usually motors burned up because they were wired incorrectly.

Last edited by JValdes; 06/24/07 12:37 PM.
JValdes #165266 06/24/07 01:21 PM
Joined: Jun 2007
Posts: 301
J
Member
Greg,
All you have to know is that the wye is for starting and the delta is for running. If you don't have a wye/delta starter config you will always use the delta.

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