STAR-DELTA MOTOR or PANEL

[jrrocks]

Stupid question..!! Please excuse me I am not electrical background but would like to know some details..

Does star-delta connection is provided at Panel or at motor?
I have seen Star-Delta simple line diagram on the surface of (3-phase 9 kW Induction Motor) wiring connection plate. So, does it means that motor itself is provided with Star-Delta inbuilt starter OR we have to design/select the panel for Star-delta starter.

 

[xnuke]

Probably neither. Without seeing a photo of the nameplate, I'm guessing it means the motor can be connected internally either in star or delta as you choose. Using a star-delta starter or starting it across-the-line would be another choice you would make depending on the voltage sag that starting the motor across-the-line might cause.

xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[jrrocks]

Hi,
I don't have photo right now but I could describe it.
In connection box of motor, there are 6 terminals. Each three are on either side, facing each other and each terminal is connected to opposite terminal with some kind conductive plate. From the plate diagram, i could guess its in delta connected.
My belief is that, motor can either connected to Delta or Star but motor itself don't have provision for changeover from star to delta.
If this is the case, I could not see Star-Delta connection in panel, though. But, yes the panel is with VFD which output is supply to this motor (9kW). So, star-delta is not required in panel, in this case?

 

[waross]

The motor is suitable for two voltages such as 230 Volts and 400 Volts.
Use delta for a 230 Volt supply and use star for a 400 Volt supply.
You may also use a star-delta starter, but only with a 230 Volt supply.
Star delta starters are not recommended. A soft start or VFD will be a better choice to reduce the starting current.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[zeusfaber]

Just to add to what the others have already said.

If you did decide to use star-delta starting (taking Bill's point that it's very rarely a good idea these days), you would completely omit the conducting links from the terminal box on the motor and bring all six leads out to a special starter panel for contactors to switch between star and delta change instead.

A

 

[jraef]

To directly answer your question though, motors don’t come with the starters that control them built-in, they are separate devices. So if you want to use star-delta as the starting method (again, not preferable), you must buy or build a start-delta starter. It’s an archaic method though and fraught with problems and potential pitfalls. The only reason people used it was because it was a cheap way to lower starting current surges, but now there are more effective, safer and less problematic ways to do it that are cost effective, especially on small motors like that. (It might seem large to you, but to those of us regularly engage in the motor world, it’s a puppy.) But even though your motor is designed to possibly use star-delta, doesn’t mean you must.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[jrrocks]

Thank you guys..!!

So I could conclude that VFD drive will eliminate the requirement of Star-Delta starter.

 

[edison123]

A VFD for 9 KW just for starting is not a great idea. What is the load this motor is driving?

Muthu

http://www.edison.co.in

 

[Skogsgurra]

As Muthu says. It has been said before and I think that you will have to accept it: The six winding ends that are present in the terminal box are available in almost all asynchronous motors and do not mean that you HAVE TO use any Wye/Delta starter. Or any VFD. Or other device - except a normal starter or even a simple ON/OFF switch.

Just make sure that the connection is right for your voltage and that the rotation is right. Set the protection. Then connect and start. There's nothing more to it.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[jraef]

If you gain something from being able to vary the speed, then yes, a VFD is a good idea. If it’s going to run at a fixed speed all of the time, a VFD will have between 3-5% losses that will add up over time. If you need to vary the speed, these losses are insignificant because they will be less losses than any other method of speed control. But if you don’t change the speed, use a solid state soft starter. At that size they likely cost close to the same, but the soft starter will not have operating losses (assuming a bypass, which most now come with).


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden