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Thread: VFDs for Newbies
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6th February 2020, 10:24 AM #1.
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VFDs for Newbies
The attached PDF document was prompted by Fletty and is drawn up to inform, especially newbies, about VFDs and includes the answers to a few common questions about VFDs.
It's main purpose is to provide members with some background so they can then talk to their sparky or technical person about VFDs. There's nothing in the document about how to wire them up etc, and I don't intend putting that information in there.
If anyone else has what might be a common question (nothing about specific wiring) that won't take too long to explain, I am happy enough to edit the document and repost.Last edited by BobL; 7th April 2020 at 01:44 PM.
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6th February 2020 10:24 AM # ADSGoogle Adsense Advertisement
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7th April 2020, 01:32 PM #2SENIOR MEMBER
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Brilliant - just brilliant! Many thanks, I'll check it out
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7th April 2020, 03:58 PM #3China
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Interesting read, even though I have three Phase, my sparky recommended using a VFD because of the control I will have, would have been a lot of mucking around to construct
otherwise.
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7th April 2020, 04:17 PM #4.
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YeP I agree, even if I had 3Phase Power in my shed I would still install VFDs on most of my machines.
I have a cousin in Italy who manufactures small electric motors. Many of his motors are 3P with built in VFDs for use in single phase situations. If he can recover from the COVID19 debacle he envisages phasing out single phase motors for all bar a few specialised situations.
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7th April 2020, 05:28 PM #5SENIOR MEMBER
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So looking at what I have none of these motors are compatible with a VFD. Message from Conon Motors:
Its not right as your motor can only runs at 415V three phase then this single phase VFD is not right for you to use.
You motor should allows you to runs at either 240V/415V then you need change your motor to Delta mode (240V three phase). Then the motor is OK to run with single phase VFD.
Single phase VFD is 240V single phase input and three phase 240V output.
20200407_161426_resized.jpg 20200407_112921_resized.jpg 20200407_112926_resized.jpgMotor HP Phase Volts AMPS RPM Cycles (Hz) RATING Crompton (Crescent Bandsaw) 2.75 3 400/440 5 940 50 CONT K. L. Electric Co. (McPherson Bandsaw) 3 3 415 4.3 1425 50 CONT Crompton (L.S. Barker Bandsaw) 5 3 400/440 7.4 1440 50 ?
What a bummer - back to the drawing board in getting a Single Phase motor for my bandsaws
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7th April 2020, 05:59 PM #6.
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The grey Crompton motor says it is 3Phase 400/440 ∆ so it simple cannot run at full power on 240V 3P and neither will conversion. If it is converted to Y it will need 690V to run at full power
The other two don't say whether they're ∆ or Y. If they're Y it may be possible to converted them to ∆ which will make them 240V 3P motors. This is s jb for a motor rewinder. Just bear in mind that if you take them an old motor they may not be prepared to convert an old motor.
I do not recommend using one VFD to operate two different motors unless they are the same speed and HP, the same performance is required of both motors, and suitable precautions taken using cross over switches etc. The technicalities are explained in that VFD for newbies doc.
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7th April 2020, 06:51 PM #7Senior Member
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As nearly as I can make out, the nameplate of the K.L.Electric motor shows "stator conn" as being star (lower RH corner). If this is the case, you could be in luck.
Chas.
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7th April 2020, 07:04 PM #8.
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8th April 2020, 08:00 AM #9SENIOR MEMBER
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Thanks all - I think for the cost and trouble I would go to a ~$200 3HP single phase motor is looking pretty attractive.
Last time I took in a motor for testing (to get specifications as the plate was damaged) it cost me $120 and didn't even end up using it. Rewinding etc as far as my knowledge goes isn't cheap either.
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17th April 2020, 12:24 PM #10SENIOR MEMBER
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So with none of my motors for the saws I have being compatible with a VFD I am exploring the option of being patient and waiting for an old motors like Crompton Parkinson that are compatible with VFDs to come up on Gumtree/eBay/FB Marketplace. I've found one but transport would make it cost prohibitive. The funny thing is I am sure there is probably 100s of motors suitable within a 150klm radius that are probably in the back of sheds just collecting dust going unused awaiting for eventual scrapping.
Like this one: A.C single phase cap start motor | Other Home & Garden | Gumtree Australia Mitchell Area - Seymour | 1241173157 which would have been perfect!
Screen Shot 2020-04-17 at 11.05.14 am.jpg Screen Shot 2020-04-17 at 11.05.27 am.jpg
Aside from Gumtree/eBay/FB Marketplace would there be any other options where I could find these old donks?
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17th April 2020, 02:13 PM #11.
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Just Heads up that single phase motors won't work on a VFD, some might run but they won't be very efficient.
Also some really old motors don't play all that well with VFDs. At the mens shed we had a Drill press with a big 1HP motor on it similar to the one in your post above. When I hooked it up to VFD it squealed and whined if i took it above about 60Hz. This has something to do with the magnetic characteristics of older type motors. The other thing is the bearings on these old motors might not be rated for higher speeds.
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17th April 2020, 06:25 PM #12
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17th April 2020, 08:37 PM #13SENIOR MEMBER
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Bit of a pipe dream trying to stick to old motors by the looks
Well the good thing is I'm not in a hurry as the saw restoration will take me quite some time - the motor being one of the last things I need to worry about.
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17th April 2020, 09:20 PM #14
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22nd April 2020, 10:27 AM #15
I was given a couple of 3 phase dust extractor units. How do I tell if they are suitable candidates for VFD to run of my single phase power supply?
Or do I need to get them checked by a suitable sparky?
These are the plates on them.
Regards,
Ray
20200422_085756.jpg20200422_085738.jpg
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