‐‐‐‐‐Original Message‐‐‐‐‐ 

From: Rob Greeson [mailto:rsg‐fp@electro‐mechanical.com]  

Sent: Wednesday, December 21, 2011 10:22 PM

To: Bob Smith

Cc: Brian Coffey; Michael Rivest; 'Christopher Bolduc'; Matthew Nardotti; 'John

Cymbalsky'; 'Richard Parker'; 'Wes Patterson'; 'Rob Greeson'; 'Eric Petersen'

Subject: RE: MVDT Scaling

All,

Thank you Bob.  Very well stated.  Actually I did look at the 150 BIL's also.  

See attached.

This analysis shows designs that are for all practical purposes perfectly

equivalent on an efficiency basis.  The following design parameters were kept the

same or nearly the same so as to have an "apples to apples"

comparison.

(1) Winding current density

(2) Flux Level

(3) Impedance

(4) Core steel

(5) Core construction

Comparing to the representative unit for DL12 (1500 KVA) I found the following.

Unit 1 ‐ 1500 KVA, 25000‐480Y, 125/10 BIL (+17.8% losses)

Unit 2 ‐ 1500 KVA, 34500‐480Y, 150/10 BIL (+29.9% losses)

Unfortunately, the first time around I believe we understated dramatically the

decrease in efficiencies at these higher BIL's.  They were only estimated with

about a 4% increase in watts over the lower BIL designs meaning that they have

had about 14% lower losses than they should have since the beginning.

As Bob said, there was not a lot of time to come up with an estimate at the

meeting and the 10% seems to be low.  It would be nice for Wes and his group to

check my numbers with some of their own designs.  A good designer can do this in

less than an hour and a half so it does not take very long.

I thank the committee for consideration in this matter.

Rob Greeson

> Brian:

>

>

>

> Rob is on vacation until next Thursday, 12/29/11; so I am reporting  

> his findings for the Federal Pacific 25 KV‐ 125 KV BIL, three phase designs.
>

>

>

> The best optimized MVDT Ventilated design at this level, that Rob  

> could obtain,  had losses that were 18% (not 10%) above the  

> "equivalent" 95 KV BIL design.  The 10% was mentioned hurriedly as an  

> estimate in one of our last MVDT meetings in Washington.  Before we  

> adopt the "increase  of 10% in losses" rule for 125 KV BIL, I would  

> like to see at least one of our other manufacturing members either  

> confirm or correct Rob's findings.  Rob did not investigate the 35 KV,  

> 150 KV BIL; but it would only be much,  much higher than 10%:  and if  

> mandated @ 10% above 95 KV BIL, it probably would not be buildable as  

> a MVDT Ventilated Design.

>

>

>

> Regards,

>

>

>

> Bob Smith, PE

>

> Product Manager

>

>

>

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>

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> From: Brian Coffey [mailto:brian.coffey@navigant.com]

> Sent: Wednesday, December 21, 2011 3:28 PM

> To: John Cymbalsky; Richard Parker; Wes Patterson; Rob Greeson; Bob  

> Smith; Eric Petersen

> Cc: Michael Rivest; Christopher Bolduc; Matthew Nardotti

> Subject: MVDT Scaling

>

>

>

> Team,

>

>

>

> I've attached a draft write‐up of the last Friday's MVDT scaling  

> discussion, as I've remembered it. Once we have reviewed and edited  

> this draft, we can distribute to the committee at‐large. Have I  

> omitted any email addresses from the call?

>

>

>

> Best,

>

>

>

> Brian

>

>
>

>

>

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