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alinwa
07-28-2018, 02:21 PM
My son just bought an old Charmilles D10 sinker EDM, a 3KW machine

He's in a residential area with no 3-Phase running to his shops. 120A service panels.

Guys on some forums are saying it "requires a rotary phase converter" while I'm suggesting a cheap VFD

Does anyone here know of situations where a VFD WILL NOT WORK to replace an old school phase converter?

retired
07-28-2018, 03:39 PM
al,
i ran a rotary and it worked fine
i have read that it really depends on load.
i never ran my lathe anywhere near full load, so it
THINK i could have done a vfd.
i am planning on a vfd when i reinstall my lathe.

brickeyee
07-28-2018, 04:00 PM
My son just bought an old Charmilles D10 sinker EDM, a 3KW machine

He's in a residential area with no 3-Phase running to his shops. 120A service panels.

Guys on some forums are saying it "requires a rotary phase converter" while I'm suggesting a cheap VFD

Does anyone here know of situations where a VFD WILL NOT WORK to replace an old school phase converter?


At this point the VFDs have dropped in price enough to be less expensive than a RPC and a lot more efficient.
Even if you never use the Variable function it produces a 'cleaner' 3-phase voltage set than all but the largest rotaries
running a far smaller load.

What voltage is the sinker motor set up for?
You will need to use the numbers off the motor itslef to set up whatever solution you end up with.

Make sure the setup is large enough even if you never approach the actual motor rating in use.
The motor will start better (faster) and run smoother with a converter that is larger than the minimum required.

Article 430 covers motors.
430.122 covers the VFD feed requirements.

NEC sections 215.2(A)(1), 220.40, 220.50, 220.12(C), 430.24, and 409.20 may be useful.

Good luck.
Especially if you get things inspected.
Many residential code officials have very limited experience and training in industrial type equipment connection.

I have met more than a few that had no real knowledge of how Article 430 and motor feeds and breakers are sized and selected.

The normal rather strict pairing of breaker size and conductor size are NOT the same as for 'general use' branch circuits.
Plenty of them barely understand the correct installation of Hermetic Compressor feed (think residential central A/C).

Induction motors and their controller equipment are designed to prevent overloading of feeders and overheating of the motor.
The breakers are solely for short circuit protection of the feeder to the motor controller.

Bob1949
07-28-2018, 05:10 PM
Al, to answer your question, there is no problem using a VFD
that is correctly chosen to convert single phase 220 vac 60 hz to three phase 60 hz 220-440 vac.
Iím a little surprised to see that the house only has 120 Amp service.
If possible, talk to a sales person about help choosing the right converter for your application,
otherwise you will have to do a little math to make that choice.

Bob

alinwa
07-28-2018, 05:12 PM
Al, to answer your question, there is no problem using a VFD
that is correctly chosen to convert single phase 220 vac 60 hz to three phase 60 hz 220-440 vac.
Iím a little surprised to see that the house only has 120 Amp service.
If possible, talk to a sales person about help choosing the right converter for your application,
otherwise you will have to do a little math to make that choice.

Bob

Home and two outbuildings, the outbuildings are served by smaller panels

TRA
07-28-2018, 07:54 PM
Home and two outbuildings, the outbuildings are served by smaller panels

Unless he's planning on moving to a different building, the first thing I'd do is bite the bullet and put in a 200A 220V feed to his outbuilding. As long as the main panel is not overloaded, just install another 200A breaker and feed the outbuilding from the main. All depending on the size of the main panel he has now. Saves on having 2 services, which can be a real can of worms.

In today's world and unless you have an anal inspector living next door, what's written on the drive is close enough. No need for any needless calculations.

Usually no one rigs up a EDM in an empty building. They breed and before you know it you have to move to bigger buildings.

TRA
07-28-2018, 08:02 PM
My son just bought an old Charmilles D10 sinker EDM, a 3KW machine

He's in a residential area with no 3-Phase running to his shops. 120A service panels.

Guys on some forums are saying it "requires a rotary phase converter" while I'm suggesting a cheap VFD

Does anyone here know of situations where a VFD WILL NOT WORK to replace an old school phase converter?

About the only thing you cannot do is disconnect the load from the drive, which is in direct violation of the codes.

alinwa
07-28-2018, 09:51 PM
Unless he's planning on moving to a different building, the first thing I'd do is bite the bullet and put in a 200A 220V feed to his outbuilding. As long as the main panel is not overloaded, just install another 200A breaker and feed the outbuilding from the main. All depending on the size of the main panel he has now. Saves on having 2 services, which can be a real can of worms.

In today's world and unless you have an anal inspector living next door, what's written on the drive is close enough. No need for any needless calculations.

Usually no one rigs up a EDM in an empty building. They breed and before you know it you have to move to bigger buildings.

Somehow I've been unclear..... the home is served by 200A and each outbuilding has a 120A 220V panel

The machine only draws 3A as I understand. I don't imagine draw being the issue

Jerry Reisdorff
07-29-2018, 11:26 AM
My son just bought an old Charmilles D10 sinker EDM, a 3KW machine

He's in a residential area with no 3-Phase running to his shops. 120A service panels.

Guys on some forums are saying it "requires a rotary phase converter" while I'm suggesting a cheap VFD

Does anyone here know of situations where a VFD WILL NOT WORK to replace an old school phase converter?

Al, the EDM does not know what produced the 3 ph power. Just make sure that the variable freqency drive (VFD) is set to the frequency that the EDM requires. Being old the EDM may not respond well to something else. Also, make sure that the VFD is capable of supplying the 3kw min and better to double that to 6 or 10... more the better.

mturner
07-29-2018, 06:55 PM
A VFD should be cheap and work just fine. Just get one designed for single phase input. Some are 3 phase in a variable frequency out. A rotary phase converter can be built with a 3 phase motor and a few run capacitors. It is cheap, quick, and easy if you have an old 3 phase motor laying around.

Michael

brickeyee
07-30-2018, 02:45 PM
As long as the main panel is not overloaded, just install another 200A breaker and feed the outbuilding from the main.


There are many panels that are not rated to have a breaker larger than 100 amps installed on the buss.
Make sure you check the specs on the panel you are feeding from.

The breaker-to-buss contact points are often not all that large or 'heavy' enough.

brickeyee
07-30-2018, 02:48 PM
A VFD should be cheap and work just fine. Just get one designed for single phase input. Some are 3 phase in a variable frequency out. A rotary phase converter can be built with a 3 phase motor and a few run capacitors. It is cheap, quick, and easy if you have an old 3 phase motor laying around.

Michael

And then you need a way to START the 3-phase 'idler' motor.
It has to spin up to at least close to operating speed to be 'captured' by the feed.
The idler motor also has to be at least as large as the motor you are trying to supply.
Larger produces a voltage closer to being balanced on the generated phase.

mturner
08-01-2018, 12:08 AM
And then you need a way to START the 3-phase 'idler' motor.
It has to spin up to at least close to operating speed to be 'captured' by the feed.
The idler motor also has to be at least as large as the motor you are trying to supply.
Larger produces a voltage closer to being balanced on the generated phase.

I used my homemade rotary phase converters for many years. Just threw a lever an they fired right up. Never had a special way to get them up to speed, other than capacitors.

Michael

TRA
08-01-2018, 02:19 AM
I used my homemade rotary phase converters for many years. Just threw a lever an they fired right up. Never had a special way to get them up to speed, other than capacitors.

Michael

I've seen rotary's that were started with a pull rope. As long as you can spool it up enough to start, ya don't need any Capacitors. They just clutter things up. NOW, if you are real ambitious you can use capacitors and use them to start the rotary. But that's a lot of jacking around that is not necessary. I built mine with a 3ph knife switch, a 20hp 3ph motor. OH ya, use at least a 1750 rpm motor, and hook it shaft to shaft to a ~2hp 1ph to spool it up. The are just plain simple to build. Farmers have been using them for many decades. Use your ambition and integrate a 3ph panel into the system and when you need another machine to hook it up, just pop in another 3 pole breaker and wire an you are good to go.

brickeyee
08-01-2018, 02:01 PM
I've seen rotary's that were started with a pull rope. As long as you can spool it up enough to start, ya don't need any Capacitors. They just clutter things up. NOW, if you are real ambitious you can use capacitors and use them to start the rotary. But that's a lot of jacking around that is not necessary. I built mine with a 3ph knife switch, a 20hp 3ph motor. OH ya, use at least a 1750 rpm motor, and hook it shaft to shaft to a ~2hp 1ph to spool it up. The are just plain simple to build. Farmers have been using them for many decades. Use your ambition and integrate a 3ph panel into the system and when you need another machine to hook it up, just pop in another 3 pole breaker and wire an you are good to go.

I have put together dozens of these over the years.

The 'final' version I made the greatest number of used a small rubber wheel on the 1-phase with a simple lever to push it against a pulley on the 3-phase to spin it up before applying power to teh 3-phase.

You could then apply the output of the 'open' leg of the idler 3-phase together with the two 240 V legs to make a 0 degree and +/- 180 degree 'phases.'
That was 'close enough' to allow aa 3-phase to start up all by itself.

There have been multiple examples of this in Fine Woodworking Magazine over the years.

Some of the older monster size (think wheels over 30 inches) handsaws had 'integrated' 3-phase motors driving them.

I had an Oliver (36 inch) that was like this.
Before the technology existed to easily control 240 V AC to even make a VFD.

It was easier to run a large idler to create a 0 degree phase between the two 180 degree legs of single split phase.

Some early versions tried to use capacitors to drag the split phase legs over a few degrees but that takes a lot of largish high voltage non-polarized capacitors.
It turned out to not be required but it does produce a slight penalty in the 3-phase motors about power.

Not enough to matter in anything except real production operation with 'full' cuts being made.

Pete Wass
08-01-2018, 06:47 PM
the new Griggly machines come three phase WITH a VFD, some of them, at least.

Pete

brickeyee
08-06-2018, 04:42 PM
the new Griggly machines come three phase WITH a VFD, some of them, at least.

Pete

The hardest part of designing with them is making sure they have adequate heat sink contact and the heat sink is
large enough with adequate air flow.

I had massive 3-phase AC electronic loads when working on this stuff.

They had there own 6 foot tall 19 inch rack with forced cooled air (we actually used a Unico high pressure A/C unit)
for that single rack of equipment.

And they still shut off on temperature occasionally with a 4-ton compressor on the roof.
Usually in the summer during the day.
We had to switch to testing well after dark, and even put additional fans on the roof for the compressor.

James Lederer
08-06-2018, 11:45 PM
I'm going to go out on a limb here and risk exposing my ignorance.

A VFD is designed to power a motor. There are many 3 phase applications that don't involve a motor, where a VFD will not work.

You can use the VFD to drive the motors on the sinker, but you cannot use it to supply power to the control system. VFD's use a bunch of "tricks" to do their magic. Motors don't mind the tricks, but many other systems will have a problem with it. In other words, a VFD should not be used as a general 3 phase power supply. It's possible that if you left the VFD locked at 60hz, it might work, but it's still converting AC to DC and then using something similar to pulse width modulation to create the 3 phase supply. Most VFD's are "smart" these days, and it will probably figure out that it's not connected to a motor and might just throw alarms.

If you need a 3 phase power supply for the entire machine, a rotary phase converter is the way to go.

Pete Wass
08-07-2018, 02:23 PM
I'm going to go out on a limb here and risk exposing my ignorance.

A VFD is designed to power a motor. There are many 3 phase applications that don't involve a motor, where a VFD will not work.

You can use the VFD to drive the motors on the sinker, but you cannot use it to supply power to the control system. VFD's use a bunch of "tricks" to do their magic. Motors don't mind the tricks, but many other systems will have a problem with it. In other words, a VFD should not be used as a general 3 phase power supply. It's possible that if you left the VFD locked at 60hz, it might work, but it's still converting AC to DC and then using something similar to pulse width modulation to create the 3 phase supply. Most VFD's are "smart" these days, and it will probably figure out that it's not connected to a motor and might just throw alarms.

If you need a 3 phase power supply for the entire machine, a rotary phase converter is the way to go.

Electronics and electrics have always been a black hole to me.

Thanks,

Pete

TRA
08-07-2018, 03:04 PM
Whether using a Rotary or a VFD, the motor is the only load per drive. With new machines with VFD spindles the spindle is the only load on the drive. Controls used on most machinery are single phase. You should never connect the control power to the wild leg of a rotary or a FVD. If you are running a simple machine like a drill press, or a machine with no controls other that an on-off switch, either type makes little difference. When you graduate up to machinery with controls, things get complicated. We build machines that can have everything corm 480 3ph down to 5 vac all in the same panel. Each voltage is dealt with a different supply.

mturner
08-09-2018, 10:45 AM
I'm going to go out on a limb here and risk exposing my ignorance.

A VFD is designed to power a motor. There are many 3 phase applications that don't involve a motor, where a VFD will not work.

You can use the VFD to drive the motors on the sinker, but you cannot use it to supply power to the control system. VFD's use a bunch of "tricks" to do their magic. Motors don't mind the tricks, but many other systems will have a problem with it. In other words, a VFD should not be used as a general 3 phase power supply. It's possible that if you left the VFD locked at 60hz, it might work, but it's still converting AC to DC and then using something similar to pulse width modulation to create the 3 phase supply. Most VFD's are "smart" these days, and it will probably figure out that it's not connected to a motor and might just throw alarms.

If you need a 3 phase power supply for the entire machine, a rotary phase converter is the way to go.

That's exactly why we used a (CNC qualified) rotary phase converter for our CNC back in Texas. Our simple rotary phase converters were not good enough, but they worked great for the manual machines. The one for the CNC was a 25HP with a ton of support electronics to clean things up a bit.

Michael

brickeyee
08-10-2018, 01:18 PM
If you need three phases at the correct angles you need either a VFD or an actual motor-alternator set.

VFDs have gotten better with new devices used to construct their output waveforms.
But the voltage and current waveforms are still not all that 'clean.'

The voltage on the 'generated' phase is also NOT all that well regulated.

The phase angles on a rotary type setup are not 120 degrees apart.
The most common is 180 degrees (from the two single phase legs) and a generated leg between them from the rotary phase converter.

The angles are close enough to get a 3-phase motor up and running though.

Since actual rated power from the machine's motor is rarely actually required (or used) the slight loss from the wrong phase angles is not all that important.

Especially once everything is up to speed and moving.
It can result in slightly less cut smoothness at low speeds and heavy cuts.

Like large low TPI cuts with a large bite.
There may not be enough stored momentum in the moving object to adequately smooth out the less than optimum phase angles driving the motor.

Use capacitors to filter and clean typical 3-phase voltage levels is a nightmare.
You must use 'non-polarized' capacitors, or polarized capacitors in series with each other to 'create' a non-polarized capacitor.
At a LARGE penalty in the capacitance. And the need in many cases for resistors (and even diodes) to make sure the voltage
on each capacitor stays in the correct allowed range.

The 'Farad' range capacitors have VERY low voltage ratings.
And stacking them for more voltage becomes ridiculous.

Rubicon Prec.
08-10-2018, 02:59 PM
I'm going to go out on a limb here and risk exposing my ignorance.

A VFD is designed to power a motor. There are many 3 phase applications that don't involve a motor, where a VFD will not work.

You can use the VFD to drive the motors on the sinker, but you cannot use it to supply power to the control system. VFD's use a bunch of "tricks" to do their magic. Motors don't mind the tricks, but many other systems will have a problem with it. In other words, a VFD should not be used as a general 3 phase power supply. It's possible that if you left the VFD locked at 60hz, it might work, but it's still converting AC to DC and then using something similar to pulse width modulation to create the 3 phase supply. Most VFD's are "smart" these days, and it will probably figure out that it's not connected to a motor and might just throw alarms.

If you need a 3 phase power supply for the entire machine, a rotary phase converter is the way to go.

I think this is the correct answer.

Even using a fairly high-end name brand VFD on my knee mill, it wouldn't work because I didn't realize there was a couple small fans to cool the spindle motor. A VFD us used for a single motor, not a full machine. I use a 40hp RPC for my turning center and would use a RPC for an EDM.