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Re: VFD Voltage/RPM fluctuating
Posted: Sun Feb 07, 2021 4:34 pm
by martyscncgarage
ChrisAttebery wrote: ↑Sat Feb 06, 2021 11:14 am
That’s great news. I added a 1mf tantalum cap to my analog output too.
Work for you Chris?
Re: VFD Voltage/RPM fluctuating
Posted: Sun Feb 07, 2021 10:16 pm
by ChrisAttebery
It helped. I still see .1-.2 Hz fluctuations on my VFD. It isn’t noticeable like it was before though. The machine plows right through aluminum.
Re: VFD Voltage/RPM fluctuating
Posted: Sun Feb 07, 2021 11:48 pm
by ShawnM
ChrisAttebery wrote: ↑Sat Feb 06, 2021 11:14 am
That’s great news. I added a 1mf tantalum cap to my analog output too.
Did you add a .1mf or a 1mf cap?
Re: VFD Voltage/RPM fluctuating
Posted: Mon Feb 08, 2021 12:32 am
by ChrisAttebery
A 1 micro Farad cap.
Re: VFD Voltage/RPM fluctuating
Posted: Mon Feb 08, 2021 2:45 pm
by eng199
Adding too much capacitance to opamp outputs can also cause stability problems. I would try 0.1uF or less. A low value resistor (10 to 50 ohm) in series between ACORN and the capacitor can also prevent oscillation from too much capacitance.
Re: VFD Voltage/RPM fluctuating
Posted: Mon Feb 08, 2021 2:51 pm
by ChrisAttebery
I'll have to see if I have anything smaller. Most of the electronics components I have are from projects 20+ years ago.
Re: VFD Voltage/RPM fluctuating
Posted: Mon Feb 08, 2021 3:05 pm
by martyscncgarage
eng199 wrote: ↑Mon Feb 08, 2021 2:45 pm
Adding too much capacitance to opamp outputs can also cause stability problems. I would try 0.1uF or less. A low value resistor (10 to 50 ohm) in series between ACORN and the capacitor can also prevent oscillation from too much capacitance.
Matt,
Could you draw a simple sketch of what you are describing and how it connects to Acorn's analog output for clarity's sake please?
In what cases might this help?
Thanks
Marty
Re: VFD Voltage/RPM fluctuating
Posted: Mon Feb 08, 2021 8:11 pm
by ShawnM
eng199 wrote: ↑Mon Feb 08, 2021 2:45 pm
Adding too much capacitance to opamp outputs can also cause stability problems. I would try 0.1uF or less. A low value resistor (10 to 50 ohm) in series between ACORN and the capacitor can also prevent oscillation from too much capacitance.
I'll give it a try, I have a few .1 uF tantalum caps laying around. #104 I think they are. My machine is pretty solid but I may even try one on mine to see if it makes a difference or not.
Re: VFD Voltage/RPM fluctuating
Posted: Wed Feb 10, 2021 12:06 am
by stutaylo
ShawnM wrote: ↑Mon Feb 08, 2021 8:11 pm
#104 I think they are. My machine is pretty solid but I may even try one on mine to see if it makes a difference or not.
Can confirm I put in a #104 (0.1uF) and have no movement at all on the Frequency
Re: VFD Voltage/RPM fluctuating
Posted: Wed Feb 10, 2021 12:40 am
by ChrisAttebery
I checked my VFD tonight. It was rock solid with a 1 micro farad cap.