RE: BiRa Ethernet Power Supply Controllers

[Emmanuel Mayssat <emayssat@outlook.com>]

We use BiRa power supplies with all our magnets.
We don't use the ethernet interface (and I don't think they are using it at SLAC either) for the following reason:
*** Don't trust the internal regulation of your power supplies ***
In practice, the PS are regulated at 10^-3 (= delta I / I), so 10A has 10mA noise.
If you want regulation at 10^-4 level, you need external feedback electronics.
(transducer --(error on I)--> controller board --(convoluted with input signal)---> input of the PS)
That feedback loop cannot use ethernet because it is too slow!!!

In practice, the current setting we trust is the one read on our calibrated transducer.
Another key advantage of this setting is that you can change the BiRa PS with a new one and the system will behave exactly the same (even so the PS may be slightly different in terms of output offset/noise/etc).

Obviously if you use the PS for something other than magnets, where the internal regulation is sufficient, then the Ethernet/EPICS interface may be useful.

I went to their website and read they support EPICS
 http://www.bira.com/products/bigen/
now I am curious too.

--
Emmanuel

> Date: Wed, 11 Sep 2013 16:39:24 -0700
> From: bomr@triumf.ca
> To: tech-talk@aps.anl.gov
> Subject: BiRa Ethernet Power Supply Controllers
>
> Hi all.
>
> Has anyone had any exeprience with BiRa Ethernet Power Supply
> Controllers? BiRa is advertising that SLAC has used them, so I would be
> happy to hear from anyone there with some firsthand knowledge.
>
> What is the nature of the EPICS support? Being ethernet, I was hoping
> for something SCPI-like, but the datasheet doesn't suggest that.
>
> Our power supply group would also like to contact anyone that may have
> knowledge of the hardware, installation, and those aspects of these devices.
>
> Thanks.
>
>
> Rod Nussbaumer
> ISAC Controls, TRIUMF
> Vancouver, Canada.
>