measuring costs on compressors star

Question

measuring costs on compressors star

kwaka (Mechanical)

(OP)

14 Nov 03 08:33

measuring costs on compressors starts

I need to be able to calculate how much in pounds £ a star delta starter would cost each time it starts a compressor

i know the voltage, the motor kw/hp, the peak current amps and the time duration for the start

Thankyou Kwaka

60hzhmmm (Electrical) · Answer 1 · 2003-11-14 13:54:24

kwaka:   You have posted this to the wrong forum.  You should've sent it to the POWER/MOTORS forum.

  Where, if you are contemplating the use of a STAR-DELTA starter you will find very little positive support as STAR-DELTA starters are generally less effective than across the line starters.

  As for cost per start,  I am assumming you're not talking about the electricity costs but the little bit of its life consumed with each start. I can't tell you what it would be..  Because:

1) I don't know what brand it is.
2) What duty cycle it is subjected to.
3) The inductive content of your load.
4) What percentage of its rating you use.
5) What its cycle life is.

  If I were you and was dead set on using a "political" starter or already am using it I would contact the maker and ask them what the cycle life of that model would be if used at your voltage with your load and duty cycle then divide the cost by their answer.

don01 (Electrical) · Answer 2 · 2003-11-23 04:40:57

kwaka,
despite englands blatant theft of the rugby cup last night here is a suggestion

you know the peak value the starter will ramp up to the star current max over the star time. then ramp up to FLC when changed over to delta.

you pay for KW/hrs at your billing rate.

if you are doing a budget number then say 1.414 * volts * amps * 0.8 * time (hrs) *rate /1000 (for KW/hrs)

If you are after more accurate numbers give your power company a buzz they will have data and may even do recording on your site for you. (present your request as an energy conservation thing)

Good luck
Don

cbarn24050 (Industrial) · Answer 3 · 2003-11-23 20:34:58

RE: measuring costs on compressors star

cbarn24050 (Industrial) 23 Nov 03 20:34

Hi Don, that sounds like sour grapes.

don01 (Electrical) · Answer 4 · 2003-11-24 03:58:22

cbarn
such an emotion would never cross my mind.
seriously though theyy did play well and can johnny kick. I'm a bit green about it maybe thats what's sour. (all said with a smile)

now I've gotta add some more technical to the post.
A while back there were some posts about using vfds for compressors. I was unbeleiving and when I got the numbers worked thru there were considerable savings if your plant had any real duty cycle.

maybe kwaka could talk to the manufacturer for start cost figures.they would include the load /unload / standby cycles as well

Don
(grumble mumble wewasrobbed)

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measuring costs on compressors star