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Thread: Yet another VFD post.
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8th Jul 2017, 09:29 PM #1Most Valued Member
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Yet another VFD post.
Gday Everyone.
I'm looking at getting a vfd to run my 3 phase mill on single phase. I've been doing a lot of reading here about these beasties and the more I read, the more confused I am becoming (that seems to happen a lot easier these days).
I intend to replace the old, original two speed motor with a single speed 2.2Kw Teco motor that I have.
My understanding is with the motor I have, when its configured in the Delta mode, it requires 220-240V three phase power. Is that correct?
teco motor .jpg
So would something like this be suitable for my motor?
The other question I have is how do I work out what size 240v circuit do I need? 15A - 20A - 25A ?
My son who is an eleco but lives interstate, is coming for a visit in a couple of months so I would like to get the cable run and have all the bits (for the dedicated circuit) ready for him to connect up.
Any advise would be greatly appreciated.
thanks in advance
Peter
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9th Jul 2017, 12:01 AM #2Member: Blue and white apron brigade
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The only reason for using more than 10A (usually 15A) GPO on a 3HP/2.2kW motor are the start up currents. If you program the VFD to have a slowish start (3 secs) you can run that motor via a VFD from a 10A GPO.
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9th Jul 2017, 01:32 AM #3My understanding is with the motor I have, when its configured in the Delta mode, it requires 220-240V three phase power. Is that correct?
My lathe has a 7.5hp motor and the biggest current I have seen it draw is 12A and that was just when I was running it pretty fast while trying it out. It is also a 2 speed motor (Delta, YY), and works in both speeds via the VFD.
Dean
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9th Jul 2017, 10:44 AM #4Most Valued Member
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Thanks for the info gents.
That has reduced the cost a bit for me already as I already have a 16amp breaker and a 15 amp GPO.
Do you have any thoughts as to the VFD I linked to?
thanks
peter
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9th Jul 2017, 11:17 AM #5Member: Blue and white apron brigade
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9th Jul 2017, 08:46 PM #6Most Valued Member
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Thanks for that Bob.
Another question
These are currently on ebay. They look very similar to the Huanyang one but slightly cheaper. (More than likely a different brand)
The slight difference in price doesnt bother me but the ebay ones are listed from a seller here in Australia where as the Huanyang is in China.
I'm wondering if you or anyone has had any problems with the Huanyang and if so how was it resolved from a warranty perspective?
I'm just thinking its easier to return something to an Australian address than a China one.
With the Huanyang unit I notice they say that they say that a braking unit is an optional extra. I dont envisage me wanting to use the machine for power tapping so is there any real need to have a braking facility? I know it might be nice to have, but essential - probably not.
Thanks for your patience in answering my questions
peter
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9th Jul 2017, 09:32 PM #7Member: Blue and white apron brigade
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They are the same unit but note they don't have a potentiometer to control speed - you would have to add that yourself.
And the other ones come with an extension cord and remote control panel holder.
All up it doesn't add up to a lot (i.e. <$10) but that depends how deft you are a basic electronics.
I haven't had any problems with these so warranty hasn't come up yet.
To add the braking unit is not a job for the faint hearted.
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9th Jul 2017, 10:17 PM #8Most Valued Member
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Thanks Bob.
I'll probably go with the Huanyang then. Interestingly, only one pic of the Huanyang listing shows a potentiometer, all the others its not there.
Thanks for your help.
regards
Peter
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9th Jul 2017, 10:24 PM #9Novice
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Those units run askpower firmware. They work fun, but they do have some quirks (e.g. if you set min freq too high it will trip on overcurrent).
Most of the small units don't actually have the capacity to add an additional braking resistor, but the internal resistance will slow down a mill etc at quick enough for most.
Note that most larger 415 motors don't have 240v delta windings, read the plate carefully.
Lots of those 'AU' sellers (like the one I bought from) are in China anyway. Mine had china post labels.
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9th Jul 2017, 10:27 PM #10Novice
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Oh and when you run in single phase convert the output power to the current on the input side to get the equivalent capacity.
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9th Jul 2017, 10:29 PM #11Most Valued Member
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Ok. I've just ordered the Huanyang.
Hopefully the delivery will be closer to the 10 day period than the 32 day.
Then the fun will begin.
peter
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9th Jul 2017, 10:31 PM #12Most Valued Member
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9th Jul 2017, 11:38 PM #13Novice
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Hi Peter
Sorry - that was a terrible explanation! I've been a lurker for ages but posted from having the same struggle years ago. Not an expert but happy to share what I've learned.
Basically the way the vfd's work is they put the line voltage through a rectifier and convert to DC. The DC charges some large capacitors, which creates the 'DC bus'.
This is then fed into mosfets (think fancy silicon relays) that then switch on and off to make the three phase output.
If you take the full load three phase current off the motor (e.g. 8.7A) multiplied by sqrt(3) that's your single phase input current.
You'll only draw full load amps when you are really working it hard, so I wouldn't sweat an amp here or there.
Some units that are 'single phase' models already have this derating but most don't. Just err on the side of larger - you'll get better filtering and larger capacitors out of it regardless.
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9th Jul 2017, 11:39 PM #14Novice
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Oh, and if you're planning on a dro use shielded cable - vfd's are really noisy electrically.
Last tip - never ever unplug the load side with the inverter on. The feedback circuit will try to go to infinity and potentially let the smoke out.
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10th Jul 2017, 07:08 PM #15Most Valued Member
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Pez
Thanks for the info.
I'm removing the old 1.5Kw , 2 speed motor and replacing it with a single speed 2.2kw motor. (motor plate pic in my first post) It definately says 220-240V when in Delta mode.
re the DRO & shielded cable. Do you mean shielded cable on the DRO or on the motor?
thanks
peter