David, You're a volt-nut too, aren't you ? Maybe motorise the variac and keep your lab at 240V +/- almost-nothing ?
On Sat, Dec 31, 2016 at 7:57 PM, Tom Miller <tmiller11...@verizon.net> wrote: > > ----- Original Message ----- From: "Dr. David Kirkby (Kirkby Microwave > Ltd)" <drkir...@kirkbymicrowave.co.uk> > To: "Discussion of precise time and frequency measurement" < > time-nuts@febo.com> > Sent: Saturday, December 31, 2016 11:01 AM > Subject: Re: [time-nuts] Anyone (ideally in the UK) got a spare rotary > knob for the 5370B TI counter? > > > > On 31 December 2016 at 13:03, EB4APL <eb4...@gmail.com> wrote: >> >> Hi, >>> >>> I'm not totally sure about the limits, but I have read several times that >>> in the UK the nominal supply voltage is 230 V +10%/−6% to accommodate the >>> fact that most supplies are in fact still 240 V. The context was that a >>> lot >>> of test equipment failed when operated at around 250 V and many input >>> capacitors (particularly the ones inside a know brand IEC socket - >>> filter) >>> caught fire. >>> >>> Wikipedia says that several areas in UK still have 250 V because this >>> value is withing the current limits. >>> >>> I think that the governing document is British Standard BS 7697: Nominal >>> voltages for low voltage public electricity supply systems — >>> (Implementation of HD 472 S1). >>> >>> Regards, >>> >>> Ignacio, EB4APL >>> >> >> >> >> Hi, >> I have just been on to the phone of a friend of mine who spent much of his >> like working in the electricity generating industry. Working at both >> Darlington (coal) and Bradwell (nuclear) power stations in the UK. Among >> many other things he said >> >> * He did not know the current specifications limits for certain, but he >> said easy to check. (What you say - 230 -6%/+10% does seem to be quoted in >> many places, but I guess I should check it out.) >> * Supply voltage is likely to be highest about at 2-3 am in Summer >> * Supply voltage is likely to be lowest on a cold Winter's afternoon. >> * Voltages in use around the county include at the least 11, 22, 33, 66, >> 132, 275 and 400 kV. >> * There's not much standardization of generator voltage - Bradwell nuclear >> power station was 11.1 kV. >> * There are taps on the 275 kV transformers to keep the 132 kV close to >> 132 >> kV >> * There are 6 taps on the 11 kV transformers feeding my house to adjust >> the >> voltage. Those can only be adjusted with the 11 kV off - they can't be >> done >> with it online. Essentially this means to change the taps, an area would >> need to be powered off. >> * If voltage is out of spec, it should be possible to get something done >> about it. >> * The electricity board can install monitor equipment. >> * Since I am right by the 11 kV transformer, and other places further >> away, >> dropping the voltage at my place might put other places too low. >> >> I think short-term I will put the auto transformer in line. I will monitor >> the mains, and report it in the summer, when I'm told it is likely to go >> higher. >> >> It hit 250.04 V in the last hour or so, but I have not seen the magic >> figure of 253 V. >> >> I'll get my 3457A calibrated by Keysight, then look to measure this and if >> appropriate make a formal request to have the voltage checked, and >> hopefully the problems would occur during the time it was monitored. >> >> Dave >> _______________________________________________ >> > > There are some devices that benefit from the higher voltage. Motors > usually run cooler and last longer due to the lower I2R losses. > Maybe just use a buck transformer in your lab for the (older) test > equipment. > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/m > ailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.