RE: [CAD_CAM_EDM_DRO] High Voltage servo cards

Thanks Wayne.

The rating does sound a little better proportioned. Rutex use a 65Amp
continuous rated FET, that rated to 40amps, and realistically only survives
with a 20 Amp set limit.



Inductance shouldn't be a problem with my motors, they are 8.1mH, and have
series resistors to bring the total resistance up to about 2.3 ohms without
wire resistance, though this does put a target stall current up to 69Amps,
which is really a bit hi, the max continuous rating on the FET being 65
Amps. I think perhaps when I put new drives in, I may well up the series
resistance a little so the stalled short circuit current is within the
servo's theoretical ability.



We know of many problems now with Rutex, think I've found most of them, have
you heard anything bad about Teknix (It's another Ausi!)

I also believe a couple of others out there are using big SEM servo's the
same as mine, which are MT30U4-57's, one guy I think is using Gecko's on
80V, anyone else got some running at high voltage?



Regs Mark



Dr. Mark Vaughan Ph'D. B.Eng. M0VAU

Managing Director

Vaughan Industries Ltd, reg in UK no 2561068

Water Care Technology Ltd, reg in UK no 4129351

Addr Unit3, Sydney House, Blackwater, Truro, Cornwall, TR4 8HH, UK.
Phone/Fax 44 1872 561288

RSGB DRM111(Cornwall)

_____

From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Wayne Weedon
Sent: 01 April 2007 16:58
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] High Voltage servo cards



Mark Vaughan wrote:

> Thanks Wayne
>
> I heard the bigger tek drives have been having problems poping fets. All
> claimed to be due to wrong inductance, but sort of sounds like joining
> another Rutex list.

Well they do take inductance seriously as it can have dramatic effect.
It's very low inductance motors that seem to be the real issue.

As for their Mosfet ratings, well just took a look at the TEK10's and
they Use IRFP4710's which have a 100v rating 72A and RDS on of
0.014Ohmns. They rate that drive at 80v 25A

Wayne.....

--
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Wayne M Weedon Email: wayne@fdos-design. <mailto:wayne%40fdos-design.com>
com
Fdos Design Poole UK
Tel +44-1202-677025 Fax +44-1202-770515 Mobile: 07774 439915

Specialists in small batch & Production Mechanical/Electrical Engineering
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