Recommend an MV motor supplier please? 1

[rinezry]

Hi there, was wondering whether anyone can point me to a manufacturer who can possibly supply a 2500hp 4kV motor?

It'll drive a booster compressor for low pressure sour gas. Due to a weak power system, there's a possibility of using a soft starter for this motor, but if I can find a motor with starting current ~3.5 times rated current, I might get away without the soft starter. American/NEMA standards only please. Thanks.

 

[maypot]

Rinezry,

You may wish to contact Teco or GEC Alsthom. According to your application, a slip ring motor with a round rotor will fit yours.

Bob

 

[electricpete]

Also Reliance, Toshiba, Siemens, Electric Machinery

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[ScottyUK]

Fuji, ABB...



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[magneticted]

A good bet is LSE ( Laurence Scott & Electromotors ) Norwich England.They manufacture low starting current desined motors 300%- 350% all the time for the oil & gas market

 

[jraef]

That size is well within the standard product range of all of the major manufacturers. Wound rotor would be one option, but that would cut down on your choices and lock you into a non-standard controller. 3.5x FLA is a very common starting current for a booster compressor using a solid state starter, it's done all the time. MV Soft starters have become standard products now from a variety of sources.

Major motor manufacturers with 5kV NEMA design offerings available in stock in the US: Siemens, ABB, Toshiba, GE, Reliance, Teco/Westinghouse, Baldor, Marathon, Tatung.

Smaller companies but specializing in MV motors: Electric Machinery, Ideal Electric, Louis Allis (not the same as of old, but focused on MV now).

I don't believe that Fuji, LSE or GEC/Alstom have product readilly available in the US, nor are they NEMA design. The same goes for Hitachi, Schorch, Hyundai, Mitsubishi and several other well known worldwide names. Most of them sell here, but mostly engineered products for special applications.

5kV soft starter manufacturers here in the US: Siemens, ABB, Toshiba, GE, Square-D/Schneider, Motortronics, Allen Bradley, Benshaw, Saftronics, Emotron

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[magneticted]

jraef, the question was starting current with 3.5 rated current without the need for soft starters.I'm not familiar with American manufacturers who can offer such designs.However I know for certain that ABB struggle with low starting current designs whether NEMA or IEC.As a matter of interest LSE have just been aquired by the owner of Louis Allis, and the owner has stated that he intends to open the US market for LSE.

 

[rinezry]

Thanks guys. LSE do offer motors with relatively low starting current. All I need to do now is convince the client that DOL is the best option cause they don't really trust the existing generators (>20yrs old) that will supply power to the compressor eventhough motor starting studies show that nothing should happen during startup. Want to avoid using softstarters/VSD if possible due to the cost/layout issues/etc.

Saying that, anyone knows a website that provides good guides on VSDs? Cheers.

 

[jraef]

Rinzrey,
Why are you so reluctant to use soft starters? They are not as expensive as you might think, maybe 20-30% more than DOL? Do not assume that because a VFD is so expensive that a soft starter is as well, they are completely different technologies, especially in MV applications. If you are concerned for your generators, I would consider them for sure.

magneticted,
How does one design a motor to take that much less starting current without giving something up, such as full speed running torque, in the process? I have read their website and see that they claim "starting current designs down to 300% FLC are available on request", but does that mean that the motor is designed for 300% starting current DOL, or that they have motors optimized to be started with soft starters? The latter seems more likely to me.

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[magneticted]

jraef, LSE low srarting current designs is based on their "Trislot Rotor" which I belive is a rotor with three rows of slots, in the outer row is a high resistance starting cage, and the two inner rows are occupied by a low resistance running winding. Not being a designer not sure how all works,, but the end result is a machine with low starting current design for DOL starting. The value of starting current depends on the applications, and for centrifugal pumps they offer 300 - 350%, whereas for high torque applications like mills the starting current would be around 400-450%flc. ( DOL )I also beleive the efficiency and slip are not comprimised, but the power factor is lower than a typical cage winding.

 

[rinezry]

jraef .... with a softstarter, you're reducing the voltage, hence motor torque is lower, hence takes motor longer to start, hence we have to review protection settings on the plant to incorporate this so that any overload doesn't trip during this time etc. Plus, the vendors we're talking to can't bring down starting current even with a softstarter; lowest they can go is 2.8 times rated current, which we can't accept (trust me this power system is that weak!). There are too many variables that need to be thought about with a softstarter. Hence the reason why a VSD is chosen instead.

OOhh .. and the fact that our client is insisting that they want a VSD as the preferred choice for this compressor.

 

[rinezry]

I know I mentioned 3.5 times earlier, but DOL is out of the question and softstarter can get starting current down to less than 2.5 times. Tried convincing the client, but they're adamant about it. They're willing to pay for it, so I don't want to say anything more.

 

[jraef]

Well, sometimes even the most logical arguments are lost on those that insist on wasting money. But when they see the quote for the VFD and want to reconsider something tat will cost 1/10th the price, (as is often the case with MV VFDs), tell them that many soft starter manufacturers will run a free Transient Motor Starting analysis for the load and power system to see in advance if the soft starter will work. I do that for my company, using SKM Power Tools TMS module. So far, we have been 100% accurate, and we always tell the customer when it will not work. Nobody wants an unsuccessful application.

That said, 250% is getting to be close to where a soft starter will not work for a compressor, but I have seen it work, depending on the compressor and motor design, and what the system will tolerate. 280% however is much more likely. Bottom line, one should not write off a particular technology without adequately investigating it.

magneticted;
Thanks for the info. Interesting enough to learn more about it.

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[motorspert]

Looks like a VSD you need then........
That makes the motor simpler
in addition to the list of manufacturers above, we have had good experiences with WEG motors, they also make a VSDsand offer 3 year warranty for when both supplied together

http://www.wegelectric.com

We have also been offered Chinese motors, "cheap as chips" as they say over here,

One other point, GEC-Alsthom now trading as Alstom

 

[stevecockerham]

We are ATB Morley, previously Morley Electric Motors of the UK and specialise in one-off AC motor applications such as this.
You can visit our website at

http://www.morleymotors.com

 

[Mendit]

You never said what the RPM required is ? you can forget wound rotor if its 2 pole. Synchronous works very well but the motor you require is only small. Maybe VFD will work for you also. Most induction motors off the shelf are 5.6 -6.3 (name plate code G)You need a code B. Check codes here

http://www.joliet-equipment.com/nema_code_ac_motors.htm

 

[aolalde]

rinezry:

I agree with your customer, if the compressor requires high torque to start properly, a VFD is the logic solution for effective torque/current this accentuated by that weak substation.
In spite of the lower initial investment Soft starters will provide a poor ratio torque/current.

 

[machmech]

Hello Rinezry

Since this is an old thread resurrected by stevecockerham I assume you have a motor by now, Just curious what did you get? and how is it working?

Chuck

 

[rinezry]

Hi all, thanks for the responses you've been providing me. Anyway, just so you know, we've gone for a VSD with an LSE motor that has a starting current of 3.5FLC. Such a waste of money considering the fact that we'll only use the softstart/bypass function of the VSD and nothing else, but like I mentioned earlier, power system's a bit dodgy, so better safe than sorry!

Not gonna get the chance to see the 2 working together till May though.

Rinezry