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Single to 3 phase vfd

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Alan Charleston15/11/2017 06:14:15
37 forum posts
6 photos

Hi,

I'm in the process of restoring an old Boxford AUD lathe. It came without a motor so I've been running it with an old 1/4 HP washing machine motor until I had the lathe running to a point where I was confident I didn't have a piece of scrap metal. I'm there now and I'm ready to splash out a bit of money on a proper motor. I'm planning on using a 750W (1 HP) 3 phase motor with a single phase to 3 phase variable frequency drive. I've got a quote for the bits locally (New Zealand). The motor is OK at $277 but the going price here for the VFD seems to be $550 - $600.

I can get something such as this

https://www.aliexpress.com/item/CE-220V-0-75KW-750W-Frequency-Converter-Single-Phase-Input-3-Phase-Output-Frequency-Inverter-For/32840280647.html?ws_ab_test=searchweb0_0,searchweb201602_1_10152_10065_10151_10344_10068_10345_10342_10547_10325_10343_10546_10340_10341_10548_10541_10562_10084_10083_10307_5680011_10175_10060_10155_10154_10056_10055_10539_10537_10312_10059_10313_10314_10534_10533_100031_10103_10073_10102_10557_10142_10107,searchweb201603_25,ppcSwitch_5&btsid=d7db39d6-79fe-4b42-97b8-b8bc600abdd9&algo_expid=15d9db68-cf5a-4ac7-9ee7-9b9014bd65fd-1&algo_pvid=15d9db68-cf5a-4ac7-9ee7-9b9014bd65fd&rmStoreLevelAB=0

from aliexpress for about $130.

Has anyone had any experience with this item or a recommendation for a suitable device from Aliexpress?

Regards,

Alan

John Haine15/11/2017 08:05:52
1569 forum posts
92 photos

I'm not sure about that one Alan but people seem to get good results from HuanYang vfds, which are also available from Aliexpress.

Micky T15/11/2017 08:29:11
avatar
35 forum posts
17 photos

I have just recently fitted a 1.5hp 3 pahse motor to my Boxford AUD on a HuanYang vfd with no problems. The vfd has been in service for about a year as it was previously fitted to my Grayson Lathe and has performed very well. even setting it up was fairly easy once I had got my head around the chinglish manual.

Mick

P.S I even made my own pendant to operate the vfd remotely 

Edited By Micky T on 15/11/2017 08:31:43

john fletcher 115/11/2017 08:31:32
350 forum posts

Hello Alan, I've 3 friends who have fitted HuanYang inverters and have no complaints what so ever. I programmed the inverts for them and made a simple program list so if you do buy one I could send you a copy. Please don't get the idea I'm an expert, just some one who got there in the end. Generally speaking it is easy to change the motor into Delta. Some one posted an excellent series of pictures on here about changing over from Star to Delta. John

Ian S C15/11/2017 10:25:23
avatar
6491 forum posts
216 photos

The two places I would inquire at are Scott Machinery, or R.R. Fisher, they are just firms I have had contact with, I'v had quite a bit of stuff from Fishers', and their prices seem reasonable. Scotts' will sell you a complete lathe either new or reconditioned.

Ian S C

Alan Charleston16/11/2017 06:21:28
37 forum posts
6 photos

Hi,

Thanks for the replies. The HuanYang vfds are a bit more expensive than the one I was looking at but still cheaper than the local quote. I'm a bit worried about the "Chinglish" manuals as raised by Mick so I may look at getting the HuanYang vfd so I can take advantage of John's offer to help with the programming.

John, what was the model number of the inverter your friends installed. The problem with sites like Aliexpress is that the choices are confusingly large. Buying from China is always a gamble but if your mates are happy this reduces the uncertainty a bit.

Thanks for the tip a bout local suppliers Ian. I'll give Fishers a ring tomorrow as well.

Regards,

Alan

Alan Charleston06/12/2017 05:10:53
37 forum posts
6 photos

Hi,

My VF drive has arrived from China. I ended up getting a WK 9000 from NFLiXin. I've bought a couple of meters of 3 core, neutral screened cable (really expensive at $25/meter) to connect the vfd to the motor, which is earthed via the screen to minimise rf interference. I've never used this wire before, and I'm not sure how to make the connection to the screen. Is a short section of the screen twisted and put into a connector close to the wire and then a piece of insulated wire to the motor earth terminal, or is a section of the screen long enough to get to the motor earth terminal twisted and insulated with some heat shrink?

If anyone has a picture of this, I would be keen to see it.

Regards,

Alan

David Jupp06/12/2017 07:24:40
436 forum posts
1 photos

The screen is not really intended as the Earth - that should be a separate core.

Easiest way to connect the screen is to use proper 'EMC' glands to suit the diameter of the cable used.

john fletcher 106/12/2017 09:33:17
350 forum posts

Back to Alan, the Huanyang inverters which several of my friends have is 2.2 KW model, didn't see a part number. I altered the maximum current to what ever size of motor they needed. One has a Harrison I think 130, with a 3HP motor, another a much smaller lathe so lowered the maximum current as per the motor name plate. Once you get the hang of pressing which button and pressing one twice its OK. I've kept a list of notes for future use. If you send me a PM with your email address I'll send you a copy. The first one we bought was £90.40 it came from Leicester and was here in 3 days. One other came from some where in Germany and it was here in less than a week, strange old World. I've had a look inside and they look very good, I have 3 inverters of other makes of so called top quality, all second hand and can't see much difference. John

David Jupp06/12/2017 09:38:30
436 forum posts
1 photos
Posted by David Jupp on 06/12/2017 07:24:40:

The screen is not really intended as the Earth - that should be a separate core.

Easiest way to connect the screen is to use proper 'EMC' glands to suit the diameter of the cable used.

That assumes the terminal box on the motor is metal - not one of those horrid plastic terminal boxes.

SillyOldDuffer06/12/2017 10:31:29
2259 forum posts
486 photos

Posted by Alan Charleston on 06/12/2017 05:10:53:

... I've bought a couple of meters of 3 core, neutral screened cable (really expensive at $25/meter) to connect the vfd to the motor, which is earthed via the screen to minimise rf interference. I've never used this wire before, and I'm not sure how to make the connection to the screen. Is a short section of the screen twisted and put into a connector close to the wire and then a piece of insulated wire to the motor earth terminal, or is a section of the screen long enough to get to the motor earth terminal twisted and insulated with some heat shrink?

If anyone has a picture of this, I would be keen to see it.

Regards,

Alan

Hi Alan,

Assuming you have metal boxes you need a Brass Cable Gland like this:

cable_gland.jpg

They usually come in pairs, one for each end of the cable. Buy the correct diameter to fit the hole in the cabinet and - if fitted - the motor end terminal box. Some equipments come with threaded cable access holes: these threads are standardised should fit a gland of the right diameter.

The earth shield is clamped, usually between two washers, by the gland directly to the metal of the cabinet. You may need to remove paint to get a good connection. There's a variant where the gland comes with internal metal fingers that are squeezed onto the screen when the gland is tightened, but same principle.

The shield is provided to reduce EMC and should be earthed as close to the entry point of the cable as possible. The longer any tail between entry and earth the more EMC effectiveness is reduced. There's controversy about whether or not a shielded cable should be earthed at both ends. If you only earth one end, it should earthed on the VFD side, not the motor.

It's a bad idea to use an EMC shield as a safety earth. Instead you need 4 core shielded cable for a three-phase motor. The fourth core is used to provide the safety earth. It is connected to an existing safety earth terminal not to the cabinet. Unlike the EMC shield which has to be kept short, the earth wire may be as long as it needs to be to reach an earth terminal inside the control box.

Don't be tempted to run a separate safety earth wire to avoid having to buy some 4-core shielded. Doing that bypasses the shielding on the 3 cores feeding the motor rendering the EMC protection ineffective. Depending on what you have an extra wire may be awkward to fit as well.

Dave

Alan Charleston07/12/2017 05:40:50
37 forum posts
6 photos

Hi All,

Thanks for the comments. For some reason I thought the screen was used as the earth lead so I bought a 3 core cable which of course was a total waste of money. Given that I made such a basic error I decided that perhaps it's not such a good idea to fiddle about with mains wiring. I've taken the motor and controller back to the motor supplier who will wire them up for me for not much more than it would have cost me for the (correct) cable and fittings.

At this stage I'm a bit annoyed with myself for being too ambitious by going for a 3 phase motor and vfd rather than a single phase motor with a reversing switch but I suppose if it works I may appreciate it.

Regards,

Alan

SillyOldDuffer07/12/2017 09:54:33
2259 forum posts
486 photos

Don't be discouraged Alan, you got very close. It will be worth it in the end - a 3-phase motor and VFD is definitely better than a single-phase motor.

If it's any consolation, even though I know all about not using screens as an earth, I absent-mindedly ordered 3-core screened for my lathe. I realised the mistake as soon as I looked at the cable closely. Too late - I'd already stripped the old wiring out...

As you say "I was a bit annoyed with myself"!

Dave

ChrisH07/12/2017 11:21:33
673 forum posts
7 photos

+1 on "don't be discouraged" Alan, once you experience the variable speed control a vfd gives you'll wonder why they aren't fitted as standard and how you ever lived without it.

One word of warning - hope it's not teaching granny to suck eggs - but watch the motor temp on low frequencies, if the motor goes too slowly it doesn't get enough cooling air, the motor fan is going too slowly to shift the air, and the motor can overheat. If you find that happening rig up a stand-alone fan to blow air over the motor, an old computer fan seems to work well (and could well be free!), but I don't go that slow for that long a time for it to have ever been a problem for me, so don't have a fan, but I do check the motor when I do.  That's usually only when screw cutting do I go that slow because I'm a bit of a scaredy cat not wanting to louse things up. But the beauty of the vfd is that I can go that slow, say 35 rpm, when I need to!

I also fixed up a rpm indicator using a package of led display, preassembled circuit board, proximity sensor and magnet got off E-Bay for about £6.50 inc delivery from Hong Kong to the UK - how did they do that for the money AND make a profit I asked myself - put the display and pcb in a little plastic box, made up a mount for the proximity sensor and magnet on the end of the head shaft and gave it a 12v dc supply and that's well worth it too - with a vfd and a variator on the lathe belt drive I didn't have a clue what revs I'd dialled in for the lathe before! See other threads on here for that - they feature the package and how to wire it up.

Chris

Edited By ChrisH on 07/12/2017 11:27:10

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