Re: 180 BPS synch? (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Tue, 17 Jul 2007 18:33:39 -0700
From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: 180 BPS synch? (fwd)

Hi Phil,

I fully agree. There are many drive configurations out there. The HP 
rating will be a sqrt(3) rating. Drives will identify the input and 
output currents, voltages, and phases. Those are important specs when 
selecting a drive. Not all drives are the same. There are a lot offshoot 
brands. ABB, Telemechanique, Yakasawa, Seimans, Toshiba, are good brands.

Drives were built for the industrial equipment industries, but they are 
also used in a variety of high end end user equipment as well. Although 
at work we use them in various manufacturing equipment, about 4 years 
ago I spec'd VFD's into our actual end user products. All of a sudden, 
we became a serious buyer of VFD's. I'm very happy to report not a 
single VFD has broken down. They are quite reliable.

I should point out, although a 3-phase motor is efficient and can be 
controlled for slowing to a stop, various speeds at various positions, 
changing maintaining torque at low and high speeds, and maintain 
specific speeds, a simple DC Motor can be used for spark gaps as well. 
My first variable speed RSG was a DC Motor simply controlled with a 
variable voltage. It's a lot easier than a VFD, but the VFD does have 
many control functions to do most anything you want it to. However, they 
are expensive without quantity price breaks.

Take care,
Bart


Tesla list wrote:

>---------- Forwarded message ----------
>Date: Tue, 17 Jul 2007 01:12:26 EDT
>From: FIFTYGUY@xxxxxxx
>To: tesla@xxxxxxxxxx
>Subject: Re: 180 BPS synch? (fwd)
>
> 
> 
>In a message dated 7/16/07 11:33:53 P.M. Eastern Daylight Time,  
>tesla@xxxxxxxxxx writes:
>
>  
>
>>>Does the VFD produce the 3 phase while operating off a single  phase, 220 
>>>volts input, or do you have 3 phase at your  home?
>>>      
>>>
>>It operates on single phase input and outputs 3 phase. It's an  inverter 
>>with bells and whistles.
>>    
>>
>
>It's  worth pointing out that a nominally 3-phase drive must be de-rated to a 
>much  lesser output when run from a single-phase power source. Some  3-phase 
>drives aren't recommended for single-phase supplies, and most  that can have 
>to be configured to do so (disabling phase-loss faults).  
>Typically, a drive rated at 5 HP with a 3-phase  supply will be rated for 
>only 3 HP from a single-phase supply. This makes  sense, if you consider the 
>sqrt(3) factor difference in kVA with the same  current and voltage. So be careful 
>when shopping/scrounging that drive to run  your RSG...
>
>
>-Phil LaBudde
>Center for the Advanced Study of Ballistic  Improbabilities
>
>
>
>
>
>
>************************************** Get a sneak peek of the all-new AOL at 
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