Subject: Re: Electronic ballasts

From: [email-masked] (Richard A Lough)
Date: Sat, 04 Nov 1995 12:13:47 GMT

[email-masked] (Geoff Cusick) wrote:

SNIP

>On investigation, we found that we could get whole VOLTS of a 32kHz sinewave by 
>simply waving a 'scope probe around in the room!

>I suspect that we had 2 problems - one electromagnetic, the other optical.  I'm not 
>sure how influential the EMC directive will be in this, since the frequency is very low. 
> Also, given the way that fluorescent lamps work, I'm not sure that there's a 
>cost-effective way of keeping the ballast switching frequency from radiating.

There are two relevant parts of the EMC directive:
one related to general levels of interference
the other specifically for lighting. Specific standards are set for
the performance of luminaires containing HF ballasts.

There is a slight difficulty in that the standards do not directly
relate the performance of the Luminaire to the Customer's EMC
requirements.

The advice I got when I asked a question is that fitness for purpose
is the criteria. So if you have an EMC problem call in the Trading
Standards Officer. (The Directive is already in place, but not yet
mandatory in respect of sales of equipment.)

I have taken your letter at face value. I should point out that _my_
expectation from the standard and the content of your letter is that
fields of the order of 1mv per metre are acceptable, and that the
wiring system attached to the luminaire has the greatest potential for
radiating EM energy. And when you are close to the Luminaire the 
level could be exceeded. From memory, the standard says 100 microvolts
per metre at 10 metres for the frequency you stated.

Hope this has clarified the issue.

Richard A Lough

---

From: Philip Anderson <[email-masked]>
Date: Mon, 6 Nov 1995 16:14:34 GMT

I'm researching an essay on high temperature superconductors for an Msc 
in Electromagnetics and would like to know if anyone has come across any 
articles on this subject in terms which an engineering student could 
understand.

Thanks.

Philip Anderson,
UWCC, Cardiff.

---

From: Philip Anderson <[email-masked]>
Date: Mon, 6 Nov 1995 16:12:16 GMT

Thanks.

Philip Anderson,
UWCC, Cardiff.

---

From: Alan \"Uncle Al\" Schwartz <[email-masked]>
Date: 6 Nov 1995 23:29:01 GMT

Both Scientific American and Science have within the past three years had 
several very nice articles on perovskite hi-temp superconductors.  

I would also look at back issues of Physics today and American Scientist.

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