225kW Variable Speed Motor 13

[Anode]

Hi All,
I was looking into some form of soft starter for a 225kW induction motor on a ship, when the thought of variable
speed drive came to mind. As the motor is driving a pump, the thought of being able to regulate the starting current as well as having speed control would be a bonus.
My question is: are induction motors suitable for use with a vsd?
Thank you in advance.

 

[JatTiw]

Induction motors rated for ASD/VFD appliction can be used. But some of imporant featuers to be considered are:
Squirrel Cage Induction Motor
Voltage, kW, 3-phase (delta or Star connected), Hz, rpm
frame size, Service factor, premium efficiency, insulation class, duty, Temp Class, Motor shall be suitable for adjustable speed drive (ASD) application, Motor shall be NEMA design class.
The differance between ASD appliction induction motor to the normal induction motor is that in ASD application motors special attention is paid to the heat losses genrated due to modulation frequencies.

 

[JohnMartin]

To add to JitTiw's comments, when contemplating applying an adjustable speed drive (asd) to an induction motor, two more things need to be considered:
(1) Motor insulation, especially end-turn insulation. A motor that is rated for inverter duty has extra insulation on the wire and in the end-turns to stand the stresses of harmonic voltage spikes and,
(2) Motor cooling. Do not attempt to operate a normal TEFC (totally enclosed fan cooled) motor anywhere near rated load at much less than 70% base speed, since the motor will not have sufficient air flow across the motor. A separately cooled motor (with blowers) can be operated at rated load at much lower speeds.

Hope this helps.

 

[dpc]

From a practical standpoint, there are thousands of applications where AFDs have been added to existing induction motors.

There can be problems, but generally they work. The most important issue to me is motor overheating. If the motor has to output the full 225 kW continuously you should make sure it has an adequate safety factor. The harmonic components in the drive output increase motor heating.

But most motors are not applied at their full output rating so this usually isn't a problem.

The drive output does increase the voltage stresses on the windings so if buying a new motor, you would want to purchase an inverter-duty motor which should have better winding insulation.

But in general, induction motors are what AFDs are intended be used with.

 

[jbartos]

Suggestion: Considering various electronic equipment close proximities on a ship, it may be a good idea to trace the Electromagnetic Interference of the VSD. Some filtering may be needed and proper equipment grounding. This is usually available in the VSD specifications, application notes or from the VSD Tech Support.

 

[jOmega]

Anode:

You stated that the 225 kW motor drives a pump.

Is the pump a centrifugal or positive displacement (piston, vane, etc.) type ?

Also, please advise the motor voltage rating.

Thanks.

 

[Anode]

Hi jOmega,

The pump is centrifugal and the power supply is 440V 60Hz.

Cheers

 

[dydt]

hi...
lots of discussion on VFD, VSD, Inverter Duty Motors and Soft Starters on this forum...take same time to search for them..you will gain more information before you make a decision

good luck
dydt

 

[jOmega]

Anode,
There are many ships at sea with VFD's driving various applications. Some are centrifugal pumps, some are bow thrustors, some are anchor winches, etc.

I would say from experience that you most likely can apply a VFD to the existing motor without having to suffer the additional expense of replacing the motor with a "VFD rated) motor. This is a variable torque application and so, as you reduce the speed, the load drops off as the square of the speed, and the power drops off as the cube of the speed. Ergo, as you reduce the operating speed, the cooling requirements are reduced accordingly.

[If this were an constant torque application; i.e., anchor winch or positive displacement pump, the answer would be different.]

Having done this many times before and not having suffered any known failures, I offer one suggestion; add a dv/dt (du/dt) filter at the output of the VFD. The VFD output connects to the filter input and the motor connects to the filter output. The filter will ensure that the voltage stress on the motor will be minimal. The concern here is that the insulation of the motor windings has aged and is more prone to voltage stress failure syndrome.

Some recommendations are: TCI's KLC filter (

http://www.transcoil.com)

or a Schaffner du/dt filter.

I'd also suggest that your specification for an appropriate VFD include the requirment that the fundamental RMS output voltage not be less than 95% of the fundamental RMS input voltage to the VFD. Some (not all) VFD manufacturers add a wee bit of 3rd harmonic injection and or limited overmodulation techniques to improve the fundamental RMS output voltage. PWM VFDs that do not utilize such techniques, can suffer up to a 15% loss in fundamental RMS output voltage.

Be sure to size the VFD based upon matching the VFD output rating to the motor nameplate amps. Remember, kW (HP) are nominal terms. All VFDs, in fact, all drives are ultimately rated in their output amperage sourcing capability.

Hope this helps.

jOmega

 

[jbartos]

Suggestion: Visit

http://www.control.com/1026163808/index_html

http://www.control.com/topic_page?use_category=engineering_cat

http://www.wegelectric.com/Newletters/Newsletter.pdf

http://www.system-directions.com/prod02.htm

http://www.lmphotonics.com/faq.htm

http://www.esmagazine.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2503,11143,00.html

http://www.stellartechsys.com/softstart.htm

etc. for more info

 

[jOmega]

JBartos:

After visiting the references you posted above, I am curious as to how they are related to the topic of this discussion thread; to wit, applying a VFD to a shipboard centrifugal pump application.

In reading the comments presented in your first reference,

http://www.control.com/1026163808/index_html

I was appalled at the incorrect statements about VFDs and their operation of ac induction motors presented by Mr. Hinton. Not Good.

Your third reference....

http://www.wegelectric.com/Newletters/Newsletter.pdf

provides no technical information to enhance this discussion thread, other than to advise that WEG makes VFDs, soft starters, and full voltage starters. Did I miss something ?

The reference to ...

http://www.esmagazine.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2503,11143,00.html

Timothy Coyle's article, is questioned as to relevance to this discussion thread. It pertains to lockout device between controller and motor and certainly is not relevant to Anode's shipboard application

Perhaps I am missing your point or the value of your contribution to this disucssion thread. If so, I look forward to your comments.

 

[jbartos]

Comment on jOmega (Electrical) Dec 31, 2002 marked ///\\\:

After visiting the references you posted above, I am curious as to how they are related to the topic of this discussion thread; to wit, applying a VFD to a shipboard centrifugal pump application.
///The original posting poses a generic question: My question is: are induction motors suitable for use with a vsd?
My postings attempt to answer it over the web links that are efficiently broadening horizons, not always 100% accurately. The 100% accuracy is met very rarely in more popular postings.\\In reading the comments presented in your first reference,

http://www.control.com/1026163808/index_html

I was appalled at the incorrect statements about VFDs and their operation of ac induction motors presented by Mr. Hinton. Not Good.
///Certainly, you are entitled to your own opinion and expertise. I think that Mr. Hinton overall posting has its merit. I agree that "They can give DC boost for helping overcome breakaway torque and they can run the motor at full torque at any speed from 50% to 150% of the motor name plate speed." is somewhat irregular posting.\\\
Your third reference....

http://www.wegelectric.com/Newletters/Newsletter.pdf

provides no technical information to enhance this discussion thread, other than to advise that WEG makes VFDs, soft starters, and full voltage starters. Did I miss something ?
///I presented this website to contribute an answer to the basic question posted in the original posting. The website categorizes products, it pertains to a prestigeous manufacturer, and it may be followed through the direct contact at the manufacturer.\\

 

[jbartos]

My previous posting continued:
The reference to ...

http://www.esmagazine.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2503,11143,00.html

Timothy Coyle's article, is questioned as to relevance to this discussion thread. It pertains to lockout device between controller and motor and certainly is not relevant to Anode's shipboard application
///I found the following relevant to the basic question in the original positing:
"Don't forget that variable-frequency-drives (vfd's), dc drives, "soft starters," and other electronic devices that supply power to motors are considered motor controllers under the NEC and must have a disconnect within sight. Modern vfd's are installed close to the motor to avoid over-voltage problems, making it difficult to keep all the vfd's in a mechanical room within sight of a single distribution panel or MCC.

As with starters, to reduce cost and size, most vfd manufacturers do not provide a disconnect switch as part of their standard drive package. If the optional input disconnect is not specified, a separate switch or circuit breaker must be installed. \\
Perhaps I am missing your point or the value of your contribution to this disucssion thread. If so, I look forward to your comments.
///Suggestion: Please, would you post the more constructive criticism next time.\\\

 

[jOmega]

JBartos:

[blue] Timothy Coyle's article, is questioned as to relevance to this discussion thread. It pertains to lockout device between controller and motor and certainly is not relevant to Anode's shipboard application[/blue]

[red]///I found the following relevant to the basic question in the original positing:
"Don't forget that variable-frequency-drives (vfd's), dc drives, "soft starters," and other electronic devices that supply power to motors are considered motor controllers under the NEC and must have a disconnect within sight. Modern vfd's are installed close to the motor to avoid over-voltage problems, making it difficult to keep all the vfd's in a mechanical room within sight of a single distribution panel or MCC.[/red]

I think you missed the point .... so, here it is again.

Anode said: "I was looking into some form of soft starter for a 225kW induction motor on a ship, when the thought of variable speed drive came to mind."

JBartos, Anode's application is aboard a ship[/].
The NEC Doesn't Apply to SHIPS !
...and so, my comments about the appropriateness of the Coyle reference stand.

Using a refrence to a non-relevant NEC requirement serves what purpose ? ? ? ?

Perhaps you'd consider starting a new thread for such side trips, so as not to obfuscate the salient points of this discussion.

 

[jbartos]

Suggestion to/Comment on the previous posting: The following is an excerpt from NFPA 70-2002 National Electrical Code:
Not Covered. This Code does not cover the following:
(1) Installations in ships, watercraft other than floating
buildings, railway rolling stock, aircraft, or automotive
vehicles other than mobile homes and recreational vehicles
FPN: Although the scope of this Code indicates that the
Code does not cover installations in ships, portions of this Code are incorporated by reference into Title 46, Code of Federal Regulations, Parts 110–113.

Therefore, I considered the NEC related to ships.

 

[jOmega]

JBartos,

Nice Try, JB. But your logic is faulty. A minor reference within... does not make the entire spec apropos.

As you yourself stated: [blue]" Although the scope of this Code indicates that the Code does not cover installations in ships..." [/blue]

Even the NEC states that it does not cover installations in ships ... as you stated.

Are you saying that we should ignore their pronouncements and denial of applicability... and accept your faulted logic based upon a general and minimal citing? I think not.

And in particular, Timothy Coyle's article is absolutely not appropriate for shipboard use. That is the issue, sir.

Using your logic, would it not be correct to say that because I use your name.... I know you personally ?

I would also refer you back to your reference:

http://www.control.com/1026163808/index_html

where Mr. Hinton's erroneous comments have been exposed.

 

[jbartos]

Suggestion to the previous posting: The "minor reference within" just remains to be seen how minor it is. Certainly, you are entitled to have your own opinion. That does not mean that you have right to impose it on other(s) at any price. By any chance, who gave you that right?

 

[jOmega]

JBartos,

I'm afraid that you give me more power than I possess. I don't determine if its a minor or major reference. That is done by those that write the specs and standards.

If you cannot discern the difference between major and minor, then further discussion here is moot.

Suffice it to say, (and I am not the only one to bring this to your attention) but your post display a pattern of throwing things into a discussion that have little relevance to the main theme of the discussion. Others have noted this and brought it to your attention. I would suggest that before posting impertinent items and references, that you carefully consider the relevance to the discussion. Remember, that the original poster is looking for answers and knowledge; not obfuscation.

Suggestion to JB: Ascertain the relevance before posting references culled from the fruits of search engines.

If you feel it beneficial to take a side trip, then please do start a new thread. This particular one has become a mess with a lot of rhetoric wasted correcting misconceptions masquerading as fact.

My apologies to the others who have had to suffer thru this.

 

[shipelec]

Anode,

I have done some research into this in the last year for several installations. I had an application where I had to change a 200 hp pump from steam driven to electric driven. Normally for shipboard use you would get a motor specified for 50 degree C temperature rise and this is sufficient for VFD use.

 

[jbartos]

Suggestion: Besides the VFD output dv/dt filters, as posted by JOmega, there are also harmonic filters for the VFD output, e.g. HarmonicGuard available at:

http://www.transcoil.com

http://www.transcoil.com/#khg

These harmonic filters trap or mitigate harmonic content on the VFD output. To have a peace of mind, one might check the VFD output for voltage harmonic content and current harmonic content. If it is high, the HarmonicGuard or equal is recommended to extend the life expectancy of the motor powered by the VFD.