VFD control voltage <signal isolator solution>

[offlanders]

Setting up a VFD for a router table and ran into something I haven't encountered with my other builds.

Acorn is providing 0-10V output to drive the VFD's speed control. On the bench the Acorn will preform as expected, giving a 0-10V output while not connected to anything. The VFD has two terminals GND and AO1 where it expects a 0-10V input (or difference) for speed control with 20KΩ impedance. In the process of testing I noticed I was not able to get the spindle over 12k rpm or about 50% speed. After some investigating with the voltmeter I discovered the 0-10V connection between the Acorn and VFD was at 4ish volts when the Acorn was at maximum output and unable to go any higher. The VFD does have a programmable value for the input voltage and corresponding speed, so when I moved the new expected voltage range to 0-4.5V the VFD was able to hit the expected 24k spindle RPM but I have a sneaking suspicion I'm missing something or I'm going to break/burn something up.

[ShawnM]

Please post a current report when asking for help. See the forum post below.

https://centroidcncforum.com/viewtopic.php?f=60&t=1043

[cncsnw]

Does your VFD really call the analog input terminal "AO1"?

That is a more common naming pattern for an analog output (e.g. speed or load monitor signal).

[offlanders]

Please post a current report when asking for help. See the forum post below.

https://centroidcncforum.com/viewtopic.php?f=60&t=1043

My apologies, attached is the report file.

The VFD is a Huanyang GT series, the specific model number is GT-7R5G-2 the manual for which is online at this location.
https://www.automationtechnologiesinc.c ... manual.pdf

To answer cncsnw question. I mistyped the terminal name, its connected to the AI1.

I've also attached images of the two cabinets, "power" side and "controls" side (please excuse the unsightly wire bundle, I'll pair that down once I finalize my connections) and a close up of the Acorn and VFD connections.

Im not sure its helpful, but the system is running with (4) Stepper Online's CL86T-V4.1 with 9.0NM steppers, each running a separate power supply. The 24v system powering the Acorn is a Meanwell NDR-120-24, supplying 5 amps.

To reiterate, by adjusting the VFD's expected incoming voltage range I can get the Acorn's output voltage of 0-4.3 volts to work in scaling the 0 to 24k rpm range. My concern is I'm potentially damaging something on the Acorn or VFD as the Acorn's normal output is 0-10V and im getting less then half of that for some reason.

Any insight would be greatly appreciated

[cncsnw]

If you disconnect the Acorn's analog signal from the VFD, and give a full-speed command, do you again get +10V?

If not, then the Acorn's analog output section has probably been damaged in some way.

If you do get +10V when disconnected from the VFD, then something about the VFD analog input is putting excessive load on the analog.

Have you tried using AI2 instead (with J16 on the "V" position, and P0.07 = 2, of course)?

[offlanders]

If I disconnect the Acorn's analog output and measure the voltage on said output, I get the expected 10V at full power setting, and very nearly 0 at the no power setting. When I initially was testing out the spindle/VFD I started in the AI2 position, however the jumper J16 position for Current vs Voltage is not very well labeled (see attached image) so to clear up any confusion I moved into the AI1 position as there was no analog current settings to concern myself with. When I did have it in the AI2 position the behavior was the same, I could get it to about 4.5 volts and no higher. Given the 20KΩ impedance on AI1 and AI2, I wouldn't think that is enough to drop the voltage by that much.

[tblough]

Well, the fact that you get 10V without the VFD connect pretty much narrows it down to the VFD loading the analog out. You might try a signal isolator:

https://www.amazon.com/Isolator-Insulat ... B09TJTCDQ8

[offlanders]

So I hooked up my lab power supply to the inputs of the VFD and got the exact current draw on the AI1 input when at 10 volts (see the image). Basically, at 10V the max power draw is 0.5mA and at 5V its 0.25mA. I was not able to find it in the instruction manual, but would anyone happen to know the max available current on the Acorn analog output? My guess is it would easily be able to handle 0.5mA but never assume.
Thanks,

[Ken Rychlik]

Try to run the spindle with a 9v battery to the vfd terminals instead of using acorn for a test. That should give you 90% of max speed and verify if the vfd is set up correctly.

[ShawnM]

I don't see your posted model number in the manual that you posted a link to. Are you sure you have the correct manual or did you type the model number incorrectly?

In the manual you linked to it states that AI1 is for -10 to +10V and that's not the input you want to use. You need to use AI2 which is 0-10v and set the jumpers properly to V for voltage.

The manual references several jumpers and for drives over 4kw it references J15 and J17 along with J16. There's no clear pic of the jumper location and layout in the manual so make sure you have these set correctly to V and not I.

If all this is correct them I'd look back at how you programmed the drive and look for an incorrect setting somewhere.