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Electricity getting very expensive in the Workshop
awemawson:
As part of my 'Electricity Reduction Exercise' I wanted to fit an 'Owl' real time monitor to my incoming three phase supply. I'd bought the monitor on eBay some time ago and knew that it worked however it's sensing current transformers that clip round the cable were too small for this massive cable. These are 70 mm csa / 225 amp rated and about 16.5 mm o/d . The sensors that I had would only accept up to 11 mm o/d.
Well it turns out Owl do make a suitable sensor but they are far from common. As luck would have it, trawling eBay produced two used ones and one brand new one that arrived today.
I've fitted them after a bit of a struggle wrangling the cables to get sufficient separation to clip the devices on.
As part of the testing I wanted a decent three phase load, so I thought that I'd run the spindle motor on the Beaver CNC lathe. A nice steady 1000 rpm, no load on it and it was drawing 30 kW :bugeye: Now the motor is rated at 26.5 kW so the remaining 3.5 kW must be the servo system, hydraulic pump etc.
Now OK it's a big beefy motor but with electricity at the price it now is that's practically £1 an hour just to spin the blooming motor :bang:
. . . . . not going to be leaving that idling to warm up in the future !
Pete49:
And we keep getting told that renewables make power cheaper. We need to get rid of subsidies on wind and solar to show the real cost to the people.
philf:
At the moment wind power is the biggest contributor at 12.95 GW, solar is 2.55 GW. Nuclear is 5.25 GW.
http://www.gridwatch.templar.co.uk/index.php
awemawson:
Well you wouldn't think I got the Maths prize at school all those years ago - that lathe motor calculation is out by a factor of ten!
30 kW at 29.48 pence per kwH is 30 x 29.49 / 100 = £8.847 per hour :bugeye:
Dare I ever turn it on again !
(oddly this morning it's drawing 26.97 kw not 30 :scratch: )
WeldingRod:
That sounds really -wrong-. A spindle motor drawing full power with no load??? It should be maybe 3kW! If it is a three phase motor rather than a vfd you might be seeing reactive power rather than real power. Or your spindle brake is on A simple rectifier input VFD will have horrid harmonics that will totally flummox cheap power measurement chips...
If you've got an IR gun or camera you might look at the motor or cables. 30 kW going into any of that will make stuff hot PDQ!
Um, now that i think more, I bet your current transformer ratio is off by ten!
Do you have any dumb three phase heaters you could turn on?
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