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Forum Index : Microcontroller and PC projects : Oh no, I am stuck with fixing Abdul's mess!
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| grumpyoldgeek Newbie  Joined: 30/07/2018 Location: United StatesPosts: 36 |
Not enough information to tell, but I've found that using a VFD instead of 2 expensive contactors can sometimes be the cheaper approach. Then all the switching becomes 5v and ground plus you have speed and braking control. |
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| PhenixRising Guru  Joined: 07/11/2023 Location: United KingdomPosts: 1346 |
Absolutely  I just fitted one to a Bridgeport mill and I'm totally impressed. The one I used was both VFD and Flux Vector. I used Flux Vector which runs smoother and quieter. I plan to get some more because I am convinced that I can close a position loop on these things. No substitute for a servo due to motor inertia but I have applications. |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 7843 |
Definitely so. However, we often found that there are possible drawbacks in some cases. Not all VFDs include an isolation contactor, which has to be capable of breaking the maximum motor load under fault and ESTOP conditions. Sometimes the VFD doesn't include output filters (usually bulky so they make the twee little box look rubbish in photos - and available at extra cost!) and that the load cable has to be screened to comply with EMC regs. Otherwise they are fine. :) The contactors themselves aren't usually too bad in cost compared to a full VFD setup. However, mechanical interlocks, auxiliary switches and, in some cases, interlocking relays all clobber the cost somewhat. Of course, some contactors are just stupidly expensive... Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1445 |
I fitted VFD's to all my machines over 15 years ago and they are all still working like new. With my bridgeport 2hp 3 phase motor and setup a single pulley so no more pulley changing for different speeds. Set the VFD to 100 Hz so double the speed and put in a 4 wire to the old controller box. So forward/Reverse Ramp or sudden stop 5K pot for speed control on/off switch and a huge E-Stop one can use the knee to press. I used Delta VFD's and for for my big lathe I used the S type so got a jog feature, now these old VFD's do have a heap of options and my mate gave me a cheat sheet so a 2HP motor thinks it's a 3.5HP motor. Being off the grid VFD's was my best solution and my old Kipoint inverter still powers every machine which aint bad as I did get that inverter in '05. |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 7843 |
Even some of the cheap end drill presses have VFDs on now. It's probably cheaper than the mechanical system when you are buying in quantity. Mind you, trying to get a spare part in five years might be impossible! Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| PhenixRising Guru Joined: 07/11/2023 Location: United KingdomPosts: 1346 |
Uncanny...Mine is a carbon copy, even down to the single pulley and 100Hz  The only difference is that I went with the remote pendant ($10). So I have an external display, pot and other controls. The original forward/reverse selector switch had failed and a replacement was ~$100. So I eliminated it and grabbed this ~$60 VFD kit. The main contactor and start/stop circuitry are untouched. I still need to hit start to latch-in the contactor and the estops still drop it. The VFD is downstream of the contactor. This sort of thing and also whatever I build, this kit is so inexpensive that my policy is to provide redundancy. I have dubbed this: MTTR-ZH (mean time to repair-zero hours). Edited 2025-05-31 21:06 by PhenixRising |
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| Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1445 |
Well to add to my list with my Wiler toolroom lathe that came with a 3 phase motor it was a no brainer to put a VFD on, so just programmed the VFD to get better motor performance and didn't even worry about an external interface as the Wiler does have the twin pulley setup for speed adjustment. Now as every machinist does need to make a 3 roller jig for rolling steel I had a brandnew worm reduction drive and I bought a new 3 motor for it. So with a spare VFD connected the 4 wire interface and it just works a treat and the best to date is 75x3mm flat bar rolled into 400mm diameter. So rolled a second on to make it 2 ply and it's now a 400ml pulley for my 16hp Listeriod engine so I can run the 5Kw gen head at 1500rpm. Still got one VFD left thats rated at 3HP input so undecided yet what use it for as yet. |
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