RE: P=VI Question C-Bus type content

["Keith Doxey" <ukha@xxxxxxx>]

Even simpler way to work it out.

As has been mentioned, power remains constant, its the voltage and current
that change. The higher the voltage the lower the current and vice-versa.

A 1A 240V dimmer = 1x240 = 240W

It is a 240W dimmer, or 480W in the case of the 2A version.

If you take Phil's transformer losses of 10%, this is an order of magnitude
less than the load in question so unless you are very close to maximum load
it can be ignored for ease of calculation.

Without any difficuly maths it is easy to see that 105 < 240 by a long
way.

Well safe :-)


Keith

www.diyha.co.uk
www.kat5.tv


> -----Original Message-----
> From: Frank Mc Alinden [mailto:fmcalind@xxxxxxx]
> Sent: 24 June 2003 07:44
> To: ukha_d@xxxxxxx
> Subject: Re: [ukha_d] P=VI Question C-Bus type content
>
>
> Hi Doogie
>             Power in = Power our (almost except as Phil has
> mentioned effieciency) so 105w / 240v = 0.43A......So the
> 1amp per channel is ok....I have 3 transformer type lamps
> each 50w on a single dimmer channel rated at 1 amp
> .........All my lites are low voltage halogen...
>
> Frank
>   ----- Original Message -----
>   From: Doogie Brodie
>   To: ukha_d@xxxxxxx
>   Sent: Tuesday, June 24, 2003 8:12 AM
>   Subject: [ukha_d] P=VI Question C-Bus type content
>
>
>   Hi guys,
>
>   At the risk of sounding blonde......
>
>   I'm trying to do some sums for a C-Bus install, and halogen
> downlighting
>   is where I'm falling over.......
>
>   2 options, low voltage or mains voltage. If low voltage, eg 12v
>   transformer supplying 105W, is this I=P/V so I=8.75A which means a
>   standard 1A or 2A C-Bus channel will not support it, or is the 105W
>   taken against the 240V supply voltage so I<0.5A so it's
> fine under one
>   C-Bus channel....?
>
>   Is the general consensus with C-Bus to go for mains voltage or low
>   voltage for halogens?
>
>   Cheers!
>
>   --
>   Doogie
>