7.5kw motor

[Darkwood]

i'd clarify that as with 3 phase motors. single phase is a much higher factor.

Yes noted should has put that but had the theme of the thread in mind :dozey:

 

[rapparee]

thanks boys

 

[telectrix]

Yes noted should has put that but had the theme of the thread in mind :dozey:

i know that, but thought some readers might not. it's a bloody good rule of thumb, a bit pessimistic with the larger size of motors, but always good to look on the bright side.

https://www.youtube.com/watch?v=SJUhlRoBL8M

 

[Darkwood]

I use it onsite for a off the cuff guide its usually slightly over the top which isn't a prob when weighing up the cable and supply for a ball park figure but of course confirmation before actually ordering must be done.... with the larger ones Ive done this rule of thumb so many times I know roughly how much to drop the figure to be pretty accurate too... won many a challenge with work colleagues over the yrs and may free sarnies to boot

 

[Besoeker]

I use it onsite for a off the cuff guide its usually slightly over the top which isn't a prob when weighing up the cable and supply for a ball park figure but of course confirmation before actually ordering must be done.... with the larger ones Ive done this rule of thumb so many times I know roughly how much to drop the figure to be pretty accurate too... won many a challenge with work colleagues over the yrs and may free sarnies to boot

I have to provide guaranteed efficiency figures at the bid stage. And these are for variable speed drives at different duty points.

It's between a rock and a hard place. Bid too low and lose the job. Too high and fail performance tests and take a swingeing financial penalty. Half a percent wrong one way or the other is all it takes to lose the job or a hundred k. Ouch doesn't have enough syllables.

That led me to develop a program to model motor performance from basic nameplate data.
It has worked for me over the years. Given me sleepless nights too.

I tried to write the stuff in such a way that others in the company could use it. Not that they ever did. It was just too easy to get me to do the stuff - and carry the can if it went pear shaped. Thankfully that hasn't happened. At least not yet.

The rigmarole for the calculations doesn't lend itself to being posted on a forum but, just for a bit of entertainment, here's a couple of the subroutines I included to validate input data:


Sub Cretin()
Title = "Not a valid entry !"
Msg = "Some motor to have such an efficiency or power factor. Try again."
Style = vbCritical + vbDefaultButton2
R = MsgBox(Msg, Style, Title, Help, Ctxt)
End Sub


Sub Imbecile()
Title = "Improbable Value !"
Msg = "The current entered does not tie up with the Voltage and Power for the machine. Check the data. A calculated value is offered as a default. If in doubt use the suggested default value but in any case there is an opportunity now to enter new values."
Style = vbCritical + vbDefaultButton2
R = MsgBox(Msg, Style, Title, Help, Ctxt)
End Sub

 

[Tiny Spark]

I love the sub names lol

 

[Besoeker]

I love the sub names lol

Oh well, I hoped it would amuse.
Lots more to it.....but not the right place,