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### Author Topic: Need help with my VFD not giving correct speed please  (Read 1940 times)

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#### Peter Knell

• 69
##### Re: Need help with my VFD not giving correct speed please
« Reply #10 on: December 05, 2017, 03:38:58 PM »
Thanks Craig.
I have tryed the CI input aswel.
These are some of the speeds i was getting when switching between the VI and CI inputs

#### joeaverage

• 5,842
##### Re: Need help with my VFD not giving correct speed please
« Reply #11 on: December 05, 2017, 03:45:43 PM »
Hi,
are they separate input pins?

It seems that the device is happier at current input than otherwise.

Still tempted to recommend feeding the input via 1k resistor and measure the voltage drop, its the classic technique
for measuring input impedance.

Craig
My wife left with my best friend...
and I miss him!

#### Peter Knell

• 69
##### Re: Need help with my VFD not giving correct speed please
« Reply #12 on: December 05, 2017, 03:52:03 PM »
Yes seperate terminals and also jumper switch for input. Im currently not with the machine but i will try connecting 1k between VI and 10v output tonight and let you know. Thanks for your ideas. Im almost at the point of binning it and getting a new one haha one with proper documents

#### Peter Knell

• 69
##### Re: Need help with my VFD not giving correct speed please
« Reply #13 on: December 06, 2017, 12:23:48 AM »
Hi Craig on with the 1k resistor between 10v output and the VI input i get 0.5v drop across resistor. With the resistor across the 10v and CI i get 8.5v drop.

#### joeaverage

• 5,842
##### Re: Need help with my VFD not giving correct speed please
« Reply #14 on: December 06, 2017, 12:40:01 AM »
Hi,
well that is some useful information.

The CV terminal input impedance:
Z=V/I  =(10-.5)/(.5/1000)= 19kOhm

The CI terminal input impedance:
Z=V/I =(10-8.5)/(8.5/1000)=176Ohm

Those numbers seem reasonable. Note that the current going into the CI terminal is 8.5mA and that was sufficient to drive it to 24000 rpm. It really
rather suggests that the voltage input terminal is faulty. Is it possible that its taken a hit?

How about connecting your 10V direct to the voltage terminal to see whether it will drive the spindle to full speed.

Shame about the documentation. I have a Delta VFD (Taiwanese) and am very happy with it and the documentation is good, as good as any US/European VFD
documentation. Must say have never been tempted to buy any Chinese brand cheaper than Delta.

Craig
My wife left with my best friend...
and I miss him!

#### Peter Knell

• 69
##### Re: Need help with my VFD not giving correct speed please
« Reply #15 on: December 06, 2017, 03:32:45 AM »
Thanks Craig. I think your right the Vi input is poked.
I am considering removing the VFD panel and mounting in the cabinet door of my Machine that way i can use and set the RPM with the panel mounted POT.
This is going to be the best think at the moment as i want it running. I have been considering a new VFD all together aswel. You trust the Delta ones then? Thank you so much for all your help i really appreciate it.

#### joeaverage

• 5,842
##### Re: Need help with my VFD not giving correct speed please
« Reply #16 on: December 06, 2017, 04:19:47 AM »
Hi,
yes I trust Delta, a lot cheaper than equivalent US/European brands but not absolute bargain basement prices either. If you go real cheap you might reasonably
expect trouble.

Delta have a couple of VFD model lines, from memory VFD-B and VFD-D. The VFD-B series has a digital frequency output that the slightly less capable series doesn't and
as I discovered when helping another guy on the forum it is very useful.

Delta also do a couple of very respectable lines of servos and drives.

Before getting too carried away and buying something new and trying to hide the fact from your wife why not use the current input?. Pretty simple circuit required
to convert to current drive. Second issue is 'do you actually require precise and agile speed control?'. I've found that most jobs I do require that I set the speed
once at the start of the job and it stays that way until the job is done hours later. All that is required is turn it on and off. Sure a hell don't need to go backwards!
I have, like many, spent a lot of time, energy and money trying to achieve the best speed control only to realise that 95% of that capacity is wasted. In my case
I wish I'd spent the extra on high pressure coolant pumps and filters rather than spindle control. It is quite possible that your existing VFD could still be used to
good advantage and you could hang onto your dollars to get something really useful, perhaps with enough left over for a bunch of flowers for your wife too...LOL.

Craig
My wife left with my best friend...
and I miss him!

#### Peter Knell

• 69
##### Re: Need help with my VFD not giving correct speed please
« Reply #17 on: December 06, 2017, 12:17:53 PM »
Well theres the thing Craig. Im single so no wife and this means ill buy two deltas one spare haha and also maybe some beers for my troubles haha.
I found this what ya recon?
0-10V to 4-20mA Isolated Voltage to Current Module Signal Conversion With Indicator Constant Current Source SCM PLC Potentiomete
http://s.aliexpress.com/vEvqMZVF
(from AliExpress Android)

#### joeaverage

• 5,842
##### Re: Need help with my VFD not giving correct speed please
« Reply #18 on: December 06, 2017, 12:23:58 PM »
Hi,
yeah that will certainly do the trick.

Craig
My wife left with my best friend...
and I miss him!

#### Peter Knell

• 69
##### Re: Need help with my VFD not giving correct speed please
« Reply #19 on: December 06, 2017, 12:25:35 PM »