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Re: 180 BPS synch? (fwd)
---------- 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)
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.
Tesla list wrote:
>---------- Forwarded message ----------
>Date: Tue, 17 Jul 2007 01:12:26 EDT
>Subject: Re: 180 BPS synch? (fwd)
>In a message dated 7/16/07 11:33:53 P.M. Eastern Daylight Time,
>>>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...
>Center for the Advanced Study of Ballistic Improbabilities
>************************************** Get a sneak peek of the all-new AOL at