VFD as a basic phase converter

Tolerent

Tolerent

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Looking to power a 3 phase 2 HP lathe with a 3 HP VFD. Selected the 3 vs 2 HP VFD to lower the load stress on the VFD. Planning to run the VFD off a disconnect from the main panel and disconnect it 90% of the time e.g. when the lathe is not in use or going to be used within a few hours. Not planning to shut the VFD off if I take a run to grab lunch or the store. Output of the VFD direct or through a disconnect or plug to line wiring for the Lathe. Not planning to use the VFD for speed control, soft starts etc. Just power to the lathe.

Is this a reasonable approach?

What wear and tear on and electrical usage from the VFD if I simply leave the VFD on all the time (anticipating the lathe runs a few hours weekly)?

What abuse to the VFD with me cycling and interrupting the load while the VFD is in a constant supply mode?

How involved to make use of the frequency control and soft start features of the VFD?

PM1340 3PH to https://www.automationdirect.com/ad...equency_drives_(vfd)/general_purpose/gs3-23p0
 
yes, this is a reasonable approach.
i have taken the very same approach and the the results have been good for 4 years of testing
i have not had a single failure on more than 20 machines equipped with cheap chinese VFD's

the fans will cycle on and off periodically.
there is not a lot of overhead current flow in the ready state, so not a tremendous amount of heat is generated.

let me be clear- you don't want to disconnect the power to the VFD while taking cuts- that's bad
if you wish to simply shut off the VFD from a ready state without taking cuts, there is no danger there.
i use Twist lock plugs on my VFD's at home and in the field. i disconnect power at the plug when i'm done with a machine.
i also have heavy duty power interlock devises that are effectively heavy duty light switches,
to disconnect power between the incoming power plug and the VFD on many devises. this is another approach you may emulate too

soft starting is very simple, most vfd's make that very easy by changing a few parameters in the set up

in the link,
that's a nice drive, but i have spent less than $100 on a VFD and got a lot of bang for my dollar.
i have a small 1.5hp single to 3 phase VFD that was less than $50 that just won't break-
i have done almost everything i can think of , including placing VFD control into the hands of Butchers-
somehow the drive survives, don't ask me how. :dunno:
 
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Most VFDs don't like to have the motor connections messed with while running. They need feedback from the motor to control the phases. Many of the cheaper units will fry if you disconnect the motor while it's running. These are not like static or rotary phase converters. The common instructions I have seen are to wire the motor directly to the VFD outputs. No switches or other controls in the path.

You don't have to allow for speed control etc.. But the VFD has to control the motor and power on/off is via the VFD.
 
ttabbal said:
Most VFDs don't like to have the motor connections messed with while running. They need feedback from the motor to control the phases. Many of the cheaper units will fry if you disconnect the motor while it's running. These are not like static or rotary phase converters. The common instructions I have seen are to wire the motor directly to the VFD outputs. No switches or other controls in the path.

You don't have to allow for speed control etc.. But the VFD has to control the motor and power on/off is via the VFD.
Click to expand...

So, are you saying I should not use the VFD to supply an outlet that powers a Lathe and then use the Lathe's native control system to control the lathe?
 
Ulma Doctor said:
yes, this is a reasonable approach.
i have taken the very same approach and the the results have been good for 4 years of testing
i have not had a single failure on more than 20 machines equipped with cheap chinese VFD's

the fans will cycle on and off periodically.
there is not a lot of overhead current flow in the ready state, so not a tremendous amount of heat is generated.

let me be clear- you don't want to disconnect the power to the VFD while taking cuts- that's bad
if you wish to simply shut off the VFD from a ready state without taking cuts, there is no danger there.
i use Twist lock plugs on my VFD's at home and in the field. i disconnect power at the plug when i'm done with a machine.
i also have heavy duty power interlock devises that are effectively heavy duty light switches,
to disconnect power between the incoming power plug and the VFD on many devises. this is another approach you may emulate too

soft starting is very simple, most vfd's make that very easy by changing a few parameters in the set up

in the link,
that's a nice drive, but i have spent less than $100 on a VFD and got a lot of bang for my dollar.
i have a small 1.5hp single to 3 phase VFD that was less than $50 that just won't break-
i have done almost everything i can think of , including placing VFD control into the hands of Butchers-
somehow the drive survives, don't ask me how. :dunno:
Click to expand...
Quick shopping found this for $207: https://www.vfds.com/variable-frequency-drives/3hp-220v-galt-electric-g200-vfd-g22s000100ul01

Link to your preferred VFD venue?
 
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I have that same drive on my mill, I have shut it off twice in about 3 years (other than the occasional power fail, like every time the wind blows over about 30 knots) The VFD is hard wired to my breaker panel, and the motor is hard wired directly to the VFD. All of the control is done at the VFD control inputs.

Under no condition do you want to disconnect the motor from the VFD when powered on. The VFD can not be used as what you might call a phase converter to supply 3 phase line power in the normal sense.

The Start/Stop, For/Rev circuits are pretty simple, and the documentation on that is very good. You will want to wire around your existing lathe controls, and use the existing lathe switches to control the VFD.
 
You buy an expensive lathe, I would not put on an inexpensive VFD. You do not need to oversize the VFD, if it is running at its rated output. A VFD should be left on as long as you need to work with it, frequent on/off cycling will lead to a faster degradation of the components, so I recommend turning off at the end of the day more for safety reasons. You also cannot use the VFD as a plug and play 3 phase generator, it needs to be directly wired to the motor and you need to use the VFD low voltage control inputs and retain the safety features of the lathe. This has been outlined on how to do this in previous posts.
www.hobby-machinist.com

Pm1340gt Lathe Basic Vfd Control Conversion Using The Stock Control Board And Switches

Many individuals buy the PM1340GT lathe as a 3 phase machine with the intent to convert it over to a VFD system, the usual VFD that is used is the Hitachi WJ200-015SF. Unfortunately the conversion often requires a somewhat complex and costly conversion process to optimize many of the VFD...
www.hobby-machinist.com www.hobby-machinist.com
 
I have a nice TECO and also the same unit as Ulma Doctor, they both provide 3 phase and will do the same job. The TECO has better instructions but I can program the cheap one with a little figuring which is necessary in either case.

Jim is right, you do not want to use a VFD to power your machine from the plug. It does take a little more work to wire it directly to the motor and control circuits but once it's done you're golden. Infinite variable speed within the range your lathe runs is really nice to have and I wouldn't be without VFD control on any serious lathe. Quite a few folks on here have done it and can probably help you out, with your background it should be fairly easy and you will know your machine better when done.

If you don't want to mess with that just get a static phase converter and hook it up like normal with the stock input. It will work fine and you won't have to modify anything.

Sounds like you've made a good choice on the lathe :encourage:

John
 
Tolerent said:
So, are you saying I should not use the VFD to supply an outlet that powers a Lathe and then use the Lathe's native control system to control the lathe?
Click to expand...

Correct. I've read that will kill VFDs. I've never tried it. If you want that sort of setup you need a static or rotary converter. You can also wire the controls to the VFD, though that gets more complicated. I built a simple control box to replace the rotary switch on the Bridgeport for that reason.

I have some plugged in all the time, and some that get disconnected. No trouble yet, but in theory the inrush surge when first powered can wear components faster.
 
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