Single phase 240v to 3 phase. Is upsizing a VFD always required?

acrosteve · Jul 13, 2017

I am looking at powering a 3phase, 2hp Harrison lathe with a VFD connected to a single phase source.

Probably going with a drive from Automation Direct.
Specs for their GS2 series drives; https://www.automationdirect.com/adc/Shopping/Catalog/Drives/GS2_(115_-z-_230_-z-_460_-z-_575_VAC_V-z-Hz_Control)/GS2_Drive_Units_(115_-z-_230_-z-_460_-z-_575_VAC)/GS2-22P0

Number of Phases 1-phase and 3-phase
Horsepower By Phase 2hp with 3-phase and 1-phase input

That leads me to believe that the de-rating may not be required. However, other research I have done says that since only a portion of the diodes are driven with a single phase source. Therefore, the derating is recommended.

Next size up in the GS2 line is a 3hp version for about $60 more

In the interest of keeping costs down, I am considered their GS1 series drives, but I have serious reservations.
https://www.automationdirect.com/adc/Shopping/Catalog/Drives/GS1_(120_-z-_230_VAC_V-z-Hz_Control)/GS1_Drive_Units_(120_-z-_230_VAC)/GS1-22P0

Number of Phases 3-phase
Horsepower By Phase 2hp with 3-phase input

That one looks like it is not suited for the application.

I anticipate setting the VFD for 60hz and adjusting the speed with the lathe gears.
But, will I need to use the VFD for the start stop function, or can I still use the lathe switches?

Thoughts?

Thanks

Jraef · Jul 13, 2017

It's not at all unusual that for 230V, 2HP and below, the VFD mfrs don't bother with making 2 different versions. The internal components at that size are basically all the same cost, so they just go ahead and size everything to allow for single phase input, then if it gets all 3 phases, so much the better. That concept used to be universal, but of late, SOME of the mfrs have taken to actually having two different versions, it likely saves a nickle or two and they want it all I guess. So you need to check, but yes, that one is like that; single or 3 phase input, no de-rating.

johansen · Jul 13, 2017

If you wire the lathe switches to the vfd control inputs, yes.

You cannot hot plug a motor into a vfd unless the vfd can handle around 6 times the "nameplate" full load amps on the motor.

Anyhow, short answer is yes you need to oversize the drive. The 3 hp 240v drives that can supposedly run on single phase, should work fine with your 2 hp motor.

The cheaper one you mentioned, not worth the risk, though it should be safe to derate it to 1hp, perhaps 1.5 hp.

I repaired a drive recently, was supposedly a 3 hp single phase rated drive. iirc, there were two, 1200uf 450 volt capacitors on the dc bus.
mouser has a capacitor that size for 20$, ripple current rating of 3 amps.
and another i just looked at, for 35$, ripple current rating of 6 amps.
$28.14, 5.5 amps.

anyhow, the difference of 60$ between those two drives could easily be just the capacitors.

Camshawn · Jul 13, 2017

Small drives quite often are made for single phase input. I have a Mitsubishi 2 hp drive that is made and marketed for single phase input ( only L1 and L2 terminals) on my 2 hp Harrison lathe. My drive trips off on over voltage on shutdown unless I use a 2 to 3 second ramp down. This is a solvable problem. I just have not gotten to it yet.
I have wired the lathe control into the VFD and am not using the forward reverse contractors.
Cam

acrosteve · Jul 13, 2017

Thanks for the responses. I know this topic has been very well covered, and covered again, but with the specific model I was looking at, it appears no derating is really necessary. Thus, my re-hashing of the subject.

However, your two responses do not agree. :scratchchin:

johansen · Jul 14, 2017

acrosteve said:
However, your two responses do not agree.

which ones?

anyhow, i wasn't really clear, my intended point in bringing up the cost of capacitors is that i do not believe cheap single phase rated vfds will operate for many thousands of hours at full load, as evidenced by the fact that legitamate capacitors rated for the task, would cost about half as much as the vfd.

Monarchist · Jul 14, 2017

acrosteve said:
Thanks for the responses. I know this topic has been very well covered, and covered again, but with the specific model I was looking at, it appears no derating is really necessary. Thus, my re-hashing of the subject.

However, your two responses do not agree.

If you want an accurate answer, quickly, and in one go, read "Jraef on VFD's":

..yes, that one is like that; single or 3 phase input, no de-rating.

Or JF RTFM.

If you want a long drawn-out discussion, read everyone else's debating points until JST arrives, tries to further your education "the hard way", eventually causes you to go and read-up in self defense so YOU can argue the debating points, next go.

All comes down to how much time you have to wa... 'er "invest" ...

JST · Jul 14, 2017

No it is not always required. TECO, Hitachi, Invertek, etc and some "house brands" (possibly made by one of the above) include single phase input units. Even ones that produce 230V 3phase from 120V single phase. Look around, they exist. Biggest ones I recall seeing were about 5 HP, there may be bigger ones.

Most VFDs will operate plenty long enough, if they come from a legitimate source (that specifically would NOT be "Huanyang" or ones that look like the Huanyang). Don't get hung up on lifetime debates.

Yes, you will want to NOT use the machine controls unless you use them to operate the VFD.

acrosteve · Jul 14, 2017

johansen said:
which ones?

anyhow, i wasn't really clear, my intended point in bringing up the cost of capacitors is that i do not believe cheap single phase rated vfds will operate for many thousands of hours at full load, as evidenced by the fact that legitamate capacitors rated for the task, would cost about half as much as the vfd.

These are the two sentences that stick out to me.

johansen said:
Anyhow, short answer is yes you need to oversize the drive. The 3 hp 240v drives that can supposedly run on single phase, should work fine with your 2 hp motor.

Jraef said:
So you need to check, but yes, that one is like that; single or 3 phase input, no de-rating.

Anyway, I did order the 2hp drive today.

CalG · Jul 14, 2017

Purchase over size , you will never regret doing so.

johansen · Jul 15, 2017

I should have put an exclamation point after "as evidenced by the fact that legitimate capacitors rated for the task, would cost about half as much as the vfd."

anyhow, yes they work fine for a few thousand, perhaps 10,000 hours!!

that's only 1 year of continuous operation :popcorn:

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