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Thread: Choosing a VFD
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6th Dec 2021, 08:08 PM #31Golden Member
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Regarding the use of a dedicated VFD for coolant pumps etc I decided to use a cheap mini drive (400W) from Aliexpress for the small pump on this machine. These little drives are quite good but because they are designed to be panel mounted I had to make a bracket to hold it and with all the wiring terminals at the very back it was rather difficult to wire up so in reality, with the extra work that was involved, it was not really worth the effort to save probably $40.00.
The next project machine, a cold saw, will have an Ecogoo for the 2 speed main motor and cheap conventional type drive from ebay for the tiny 3ph coolant pump.
The panel mount VFD is on the right in the photo below.
Attachment 395258
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6th Dec 2021, 08:29 PM #32Most Valued Member
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FWIW - single phase coolant pumps can be bought from AliExpress for $90 delivered.
Steve
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6th Dec 2021, 09:09 PM #33Member: Blue and white apron brigade
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Or, if you want to go super cheap, on my lathe I've been using a $30 water feature pump for more than 10 years - once set up it's produced minimal problems.
Unlike my bandsaw (which had the same pump) where the fines clogged the permanent magnet motor so that it had to be repeatedly cleaned, I gave up on this pump and used a washing machine pump.
The water feature pump has high flow (750L/hour or 12.5L/min) up to 1m in height, it can pump higher but at lower flow rate..
This means the fluid can be constantly recirculated as an open loop and a small bleed off taken off for lube coolant.
The open loop fluid line gurgles and bubbles its way and drops into the tank thus entrapping air which eliminates most bugs so coolant stink is reduced.
The drain from the lathe has a flywire and magnets in a trap.
The other alternative if you have compressed air available is a misting system. I have this on both my mill and lathe but am still using flood coolant up on the lathe. The brew I use for the mister is an ATF/kero mixture. I wouldn't call myself a big mill user but in 2 years I've used less than half a litre of brew.
The photos off my lathe open loop pump have been lost from the forum so here they are again for anyone that's interested.
The fluid is constantly pumped in a clockwise direction around the White PVC loop.
The black tank is a steel transformer oil tank (yes I was careful cleaning it out)
The black funnel which has the flywire/magnetic filter in it, is located just under the lathe drain..
wholetank.jpg
The silver tap (usually wide open) controls the open loop flow rate while the red handed tap controls flow to the lathe.
Using the two taps provides very fine control of fluid. much better than a single tap.
machinetaps.jpg
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6th Dec 2021, 09:11 PM #34Golden Member
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Yes, I realise that, but this one is an integral part of the machines tank which forms the base of the saw so by leaving it in place no plumbing modifications are required.
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18th Dec 2021, 05:04 PM #35Intermediate Member
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- Geelong
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Just wondering, are you guys using any rfi or emi filters, or line reactors on your VFD setups? Has anyone experienced any interference problems without them?
I am building a heavy duty cnc router that will have an 1kw 3ph induction motor powered spindle, run by a vfd. I would like to make sure im keeping any interference to a minimum.
I watched a video by that fella Clough42 (electronic lead screw guy) who runs through his vfd setup for his new spindle. As well as line filters, he runs the output lines from the vfd through a toroid to suppress high frequency interference.
So i guess a better question would be, what supporting products do you use in your Vfd setups, and where have you found is the best place to source these products?
Cheers, Rowdy
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18th Dec 2021, 08:22 PM #36Golden Member
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After watching Clough's video a few months ago I decided to get one of the EMI Filters that he used and it did help reduce the interference with the radio but it did not completely eliminate it, at least now I can hear the radio with the machine running whereas before the reception was completely wiped out.
I have a couple of machines fitted with LG VFD's and they are really well filtered internally, no additional filtering is required.
The EMI filter is under the 2 VFD's in this photo.
Sunnen VFD's (2).jpg
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18th Dec 2021, 08:39 PM #37
Hi Rowdy, Guys,
A cheap source of line filters is old scrap washing machines ! The scrap yards here don't bother removing them since there is very little of value inside them.
By law if they contain any type of electronic speed control, they have to have a line filter fitted. They are usually located very near the place where the mains cable enters the machine and because these machines have a two or three KW water heater they are usually rated at about 10 amps or more. Some are tubular and some are rectangular, but all have to be earthed to the machine case as well as the incoming earth.
Most have push on tag connections, though a few are wire ended.
HTH.Best Regards:
Baron J.
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18th Dec 2021, 10:38 PM #38Member: Blue and white apron brigade
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A crude way I assessed the RF output from the 9 VFDs (0.4 - 4kW) I have in my shed as using AM and FM band radio. I did not set out to do this deliberately - I usually listen to AM radio and noticed as I installed more and more VFDs the radio reception got worse to the point where I could not listen to the radio.
The RFI is present in two forms - straight radiation, and transmitted back down the power line
Not being able to listen to the radio did not worry me as I just moved to a digital radio.
What worried me more was the RFI on the electronic systems of various sensors and microprocessors I run in the shed.
The most affected sensors were the temperature sensors on the dust collector motor and external housing.,
Despite trying a number of different RFI power filters, shields, earths, ferrite toroids and chokes, and also different sensors I have never been able to resolve this .
The system I have put most effort into is the small VFD on my coffee machine pump in the kitchen. I have an Arduino box linked to the coffee machine that monitors various sensors, and the temperature sensor inout and hence output would go haywire only when the VFD was just switched (ie motor did not need to be running). Eventually I was able to suppress (but not eliminate) this to at least get a half meaningful averaged temp reading over a few second.
I ended up getting minimal interference by
- winding the temp sensor wire multiple >10x around an 8mm clip on cable core
- using ferrite toroids on the VFD output and input power
- Using an earthed Sheilded power cable from the VFD to the motor.
- wrapping the VFD in Al foil and earthing that.
Of those the most significant thing is the first one.
Nothing else in tha house or shed seems to be affected to this extent by the VFDs. Although I have heard of WIFI systems being affected - it doesn't affect mine in the shed which has a receive/send base station inside the shed.
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18th Dec 2021, 10:57 PM #39
Hi Bob, Guys,
Yes I agree !
Basically suppressing radiated interference requires complete shielding, ie a metal enclosure, but you do have to take particular care to prevent radiated interference by conduction as well. This means preventing interference flowing down any wire or cable in or out of the shielding. In general one technique is of little use without the other.
Note the mains filters that I mentioned, they are always in a earthed shielded metal box and that includes the steel cabinet of the appliance that they are mounted inside.Best Regards:
Baron J.
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19th Dec 2021, 10:23 AM #40Golden Member
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A simple way to see if the wires need shielding is to wrap the wires in Alfoil and earth to the shed wall. If the problem you are chasing goes away the wires need shielding.
Steve
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19th Dec 2021, 11:02 AM #41Most Valued Member
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I put filters on all of my VFD's....cant hear Radio GaGa without them
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19th Dec 2021, 11:50 AM #42Member: Blue and white apron brigade
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A few years ago following a major clean out at the mens shed I scored a small roll of 1.5mm shielded 6 core cable and this is what I used on the coffee machine VFD. Hate to think of what it would cost.
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22nd Dec 2021, 06:14 PM #43Senior Member
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I dothink it’s easier and cheaper to replace the whole motor. I bought a 3 hp single phase one recently, had the choice of three different speeds, and it cost $190 shipped.
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22nd Dec 2021, 07:50 PM #44
Hi Guys,
The interference problem is not the motor ! But the VFD driving it, producing interference that is both conducted to the motor and radiated from the wiring connected to it.Best Regards:
Baron J.
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22nd Dec 2021, 11:07 PM #45Most Valued Member
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If you have concerns around EME put the money you are going to spend mucking about with shielding and ferrites and whatever other voodoo you choose to try and suppress it with and throw it at buying a better VFD that is compliant for EME/RFI to start with. Doesn’t really make sense to buy a hundred dollar VFD and then throw two hundred dollars worth of shielded cable and ferrites and line reg modules at the problem when three hundred spent on a name brand VFD with EME compliance would not have the problem to begin with. I know… it’s an inconvenient truth that doesn’t justify the hoarding that is commonly seen amongst those that do such things
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