Feasibility of Changing Over 3 ph motor on Trak 1440 to 1 phase

[UtahSmitty]

I am basically a hobby machinist who does odd jobs on the side.

I bought a Trak 1440 S lathe last summer, and, now that my shop is close to being finished, I'm looking at how to install it.

Even though its a CNC lathe, you get various spindle speeds via a manually shifted gear box and a 2 speed, 3 phase motor.

My biggest concern is how to operate it's 2 speed 3 phase motor on single phase power. The motor is rated at 2.5hp/4.5hp. I would like to use a VFD to operate the lathe but I contacted Southwestern Industries, and they said I need to use a computer quality rotary phase converter (RPC) at double the motor hp.

When I contacted a company about getting a RPC, I was told that I needed a 15 hp PRC--it seems they added the individual hp of each speed range and doubled it, rather than rate it from the highest hp of the motor. IOW, if I have to get a RPC, I'm hoping a 10 hp RPC should work, instead of a 15hp.

Even so, aside from the high cost of the RPC, it wouldn't be very energy efficient.

I'm not an electrician, but looking at the wiring diagram, it appears that only the motor and the coolant pump run on 3 phase 220 V. The voltage is reduced to 115V for the controls and servo motors.

Would it be feasible to replace the 3 phase motor with a single phase 220v motor, and hook up the other electrical components separately? Or, run just the motor with a Variable Frequency Drive and power the other components separately?

I've uploaded some pictures of the components in the electrical panel as well as wiring diagrams... hopefully they will help--they're over my head.

Any thoughts or input would be greatly appreciated.

Regards,

Smitty

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[joeavaerage]

Hi,

My biggest concern is how to operate it's 2 speed 3 phase motor on single phase power. The motor is rated at 2.5hp/4.5hp

This is a common problem and most newcomers to the field are flabbergasted at the (electrical) power required to drive a spindle motor and even
more preplexed at why it seems that VFDs require something like twice the input power compared to the motor that its supposed to drive.

You can get 2hp and 3hp single phase motors (230V) but they are big, double and more the size of a three phase motor of the same power and they have
VERY demanding start up input current. They are really expesive to boot.

I would suggest rather than replace the three phase motor with single phase you should follow up the idea of a RPC or a VFD.

VFD's can be supplied by single phase (230V) power but 2.2 kw or 3hp is about the practical limit. Even such a device could consume 20-30A from
a single phase supply and you will have to have a dedicated circuit with heavy duty wiring and fusing/circuit breakers to do it.

The upshot is that VFD's are high speed switching devices and the distortion caused by the extremely discontinuous current demand results
in power factors as low as 0.5. That means that you could put in 1kW but only get 'effectively' 500W out. For low power devices such as hobby
machines such a low power factor is acceptable, after all we still don't use that much electricity.

In an industrial situation such a low power factor means expensive power bills and also the the power supply is 'polluted' by such a device. The
corrective procedure for VFD's, RPC's and big servo drives is the use of line reactors. They are big iron core coils, not dissimlar to a big
transformer, on the input side of the device. A good line reactor will increase the power factor to 0.8 to 0.9 ( 1.0 is the unobtainable pefect goal)
which saves money and prevents the power supply company getting on your case.

If you wish to use a VFD you will need one probably 4-5 kW. It would ideally be fed with three phase AC input but they will work, with a sufficent
de-rating, with single phase (230V) input. You will almost certainly be required to fit a big kick-arse line reactor otherwise your single phase supply
is going to blow up. You will need a dedicated circuit with an absolute minium of 30A, but better to have your electrician install wiring and breakers
to accomodate a 50A circuit.

Most necomers dissmiss the idea of having the power company install a three phase connection to your workshop as too expensive.
When you consider the cost of an outsized VFD, the cost of installing a 50A circuit and breakers and the cost of a good line reactor then suddenly
the cost of a three phase supply does not seem so extravagent any more.

I live in New Zealand and so the numbers I quote hereafter refer to NZD and the electrical standards are determined by NZ Standards. Having
said that, similar standards apply throughout the world, after all 'is it safe' is the same question asked everywhere.

When my house was rewired recently I investigated having a three phase supply. It was going to cost $1500, whereas the single phase supply cost
$680. The kicker was that if I wanted three phase I had to guaruntee a minimum supply period of five years and a minimum monthly energy
demand.

I reasoned that the single phase pole fuse and aerial lead-in are rated to 80A, and the power-meter and isolation breaker are rated to 63A which
meant I could have a dedicated 50A circuit if I was prepared to turn off things like my electric oven and hot water when I want to use my mill,
that would be adequte. I settled for a single phase supply which had no monthly energy demand requirement because I use very little electricity
overall.

To sum up, yes you can run your lathe with a single phase supply IF you are preapred to have a very heavy duty single phase circuit installed and equip
it with an out-sized VFD and line reactors.

The question is does the single phase solution cost as much, or worse, more than having three phase installed?

Craig

[Jim Dawson]

According to the schematic, the only device in the system that requires 3 phase power is the spindle motor. Everything else comes off of the transformer and is single phase. It looks like the coolant pump is 120V single phase.

So a couple of options:

Run the spindle motor on a single phase rated, 5 HP VFD

or

Power the lathe up with about a 7.5 HP RPC, taking care when installed that the manufactured leg only goes to the motor circuit.

[UtahSmitty]

Thanks, Craig for some good info and feedback.

I have a 200 amp panel wired into my shop, and have dedicated 50 amp 240 volt lines available for my machines. I have a Bridgeport-style manual mill with 3 hp, a small manual lathe with 3/4 hp 220V, welders, and various large wood working tools, including a table saw with a 7.5 hp motor.

Getting 3 phase power to my shop isn't really feasible for the same reasons you gave in your post. The manufacturer told me I need to use a RPC for the lathe, with a rating double the rated hp. A VFD won't work for powering the machine overall because the other electrical components of the lathe are fed from the same 240 V 3 ph input. 10 hp sucks a lot of juice.

I put a VFD on my 3 ph mill and put choke coils and a line conditioner on it, but I suspect its still putting out all kinds of electromagnetic energy that will play havoc with computers, etc. I'm not skilled enough nor do I have the equipment I need to verify what it's doing... I guess I'll find out when I hook up my CNC machines.

Thanks again for your reply.

Smitty

[UtahSmitty]

According to the schematic, the only device in the system that requires 3 phase power is the spindle motor. Everything else comes off of the transformer and is single phase. It looks like the coolant pump is 120V single phase.

So a couple of options:

Run the spindle motor on a single phase rated, 5 HP VFD

or

Power the lathe up with about a 7.5 HP RPC, taking care when installed that the manufactured leg only goes to the motor circuit.

Thanks for the suggestions, Jim.

I'm not quite sure what you mean about the manufactured leg going to the motor circuit... is this the additional leg that is provided by the RPC?

Thanks,

Smitty

[Jim Dawson]

Thanks for the suggestions, Jim.

I'm not quite sure what you mean about the manufactured leg going to the motor circuit... is this the additional leg that is provided by the RPC?

Thanks,

Smitty

My pleasure.

Yes, the additional leg provided by the RPC.

Just to put everything in perspective, I'm running several VFDs in my shop with no problems, and none have filters. I also have a RPC connected to my 10HP spindle lathe. It's a 15HP RPC, that also runs the 3 HP hydraulic pump and the two 1/2 HP coolant pumps, as well as the four 1.8KW servos for the axis drives.

[hanermo]

Em..
VFDs are actually pretty efficient and will pretty much output what is input, in terms of power, that is measured in kW.

If a 2.2 kW VFD actually lost 0.5 times it´s power, it would need to heat 1.1 kW of waste losses at the VFD and or the motor.
A 2 kW heater warms up a room, quickly, and small saunas can work with 2 kW.

A 1 kW loss at the VFD, with typical plastic housing, would quickly melt the housing and the solder and burn the electronic components inside.

This does not mean the VFD is efficient, aka the losses occur at the motor end as well.

In the real world, most usage (98%) of machine tools is at very low loads compared to max capacity.
And a 5 Hp 3-phase motor will run perfectly well off a 2 hp vfd, forever, it just will only deliver 2 hp of output power.
Which is more than enough, in the real world, mostly.

Things like running large diameter insert drills into tool steel blanks like molds require huge power, 20 HP+, 2"/50mm D drills.
This is not prototrak territory.
Likewise running medium size high-feed milling cutters (10-12 mm D) at 12.000 rpm and 200 ipm feeds like on Brother drill/tap speedio machines, are impossible on a prototrak.

My big VMC, scratch built, now has a 2.2 kW Hitachi VFD and a 2.2 kW 3 phase motor.
It is very much better than any industrial induction motor, like the 1.5 kW motor on the lathe originally.

But the 2.5 kW AC servo motor on the lathe spindle now is (quite a lot) better than the 11 kW industrial Haas ST10 lathe spindle motor.

3 phase motors are much better than induction motors. Much.
And VFDs and 3 phase motors are cheap, and You can oversize each for peanuts and have them run cool forever.
AC servo drives are 5x better, but cost quite a lot.

[joeavaerage]

Hi,

If a 2.2 kW VFD actually lost 0.5 times it´s power, it would need to heat 1.1 kW of waste losses at the VFD and or the motor.

That is incorrect, this is called power factor, it does not mean that 1kw is dissapated as heat in the VFD.

Craig

[joeavaerage]

Hi,

Have a look at this publication by Yaskawa:

https://www.yaskawa.com/delegate/get...=WP.AFD.10.pdf

In particular look at the formula published to calculate power factor and note how depenant it is on THD (Total Harmonic Distotrion)
and that by definition VFD's have VERY HIGH harmonic distortion.

The upshot is that a VFD (or RPC or servo drive or any other unmodified rectifier/capacitor input inverter) will appear to asborb much more
current than it outputs. The extra current is not dissapted as heat but reflected back into the supply, traditionally called 'reactive current'.
In the case of VFD's this is beacuse of the distorted current waveform. For small installations you can ignore it but for large installions the power
company will insist you improve the power factor or 'supply pollution' to protect their network and other customers installations.

Even in small installations a low power factor will stress your supply, the current going into the device might be 30A but the output only 20A.
If you use line reactors the input current will reduce to say 22A and the output is still 20A. If you have a 25A breaker then it will pop in the
without the use of line reactors but it will operate normally with line reactors.

Craig

[mactec54]

I am basically a hobby machinist who does odd jobs on the side.

I bought a Trak 1440 S lathe last summer, and, now that my shop is close to being finished, I'm looking at how to install it.

Even though its a CNC lathe, you get various spindle speeds via a manually shifted gear box and a 2 speed, 3 phase motor.

My biggest concern is how to operate it's 2 speed 3 phase motor on single phase power. The motor is rated at 2.5hp/4.5hp. I would like to use a VFD to operate the lathe but I contacted Southwestern Industries, and they said I need to use a computer quality rotary phase converter (RPC) at double the motor hp.

When I contacted a company about getting a RPC, I was told that I needed a 15 hp PRC--it seems they added the individual hp of each speed range and doubled it, rather than rate it from the highest hp of the motor. IOW, if I have to get a RPC, I'm hoping a 10 hp RPC should work, instead of a 15hp.

Even so, aside from the high cost of the RPC, it wouldn't be very energy efficient.

I'm not an electrician, but looking at the wiring diagram, it appears that only the motor and the coolant pump run on 3 phase 220 V. The voltage is reduced to 115V for the controls and servo motors.

Would it be feasible to replace the 3 phase motor with a single phase 220v motor, and hook up the other electrical components separately? Or, run just the motor with a Variable Frequency Drive and power the other components separately?

I've uploaded some pictures of the components in the electrical panel as well as wiring diagrams... hopefully they will help--they're over my head.

Any thoughts or input would be greatly appreciated.

Regards,

Smitty

Yes you could use a VFD Drive for your spindle motor control, but you can only use one of the motor speeds so when you wire it up you will select the more used speed range and then use the VFD to change the speeds up to 120Hz for the spindle motor

When sizing the VFD Drive for a Mill and using 240v single phase power 2Hp larger then the motor Hp is a good starting point, this can depend if the VFD Drive is 3 Ph or has a single phase rating

You do not need a line reactor just a EMI power Filter is all that is need on the input power supply to the VFD Drive this should be placed close to the VFD Drive

RPC's I'm not a fan as they are so inefficient

Don't take to much notice of what joeavaerage has posted as it appears that he is way over his head in this subject

[mactec54]

Hi,

Have a look at this publication by Yaskawa:

https://www.yaskawa.com/delegate/get...=WP.AFD.10.pdf

In particular look at the formula published to calculate power factor and note how depenant it is on THD (Total Harmonic Distotrion)
and that by definition VFD's have VERY HIGH harmonic distortion.

The upshot is that a VFD (or RPC or servo drive or any other unmodified rectifier/capacitor input inverter) will appear to asborb much more
current than it outputs. The extra current is not dissapted as heat but reflected back into the supply, traditionally called 'reactive current'.
In the case of VFD's this is beacuse of the distorted current waveform. For small installations you can ignore it but for large installions the power
company will insist you improve the power factor or 'supply pollution' to protect their network and other customers installations.

Even in small installations a low power factor will stress your supply, the current going into the device might be 30A but the output only 20A.
If you use line reactors the input current will reduce to say 22A and the output is still 20A. If you have a 25A breaker then it will pop in the
without the use of line reactors but it will operate normally with line reactors.

Craig

You seem to be confused again the Power factor of most VFD Drives is usually around 0 .95 power factor or greater, a VFD Drive improves the power factor so why are you even talking about it

[hanermo]

Nah.
If power is input, it is output as either heat or work.

If You can demonstrate otherwise, disproving Newton 2, You get a Nobel prize.
If You can can output more than input, You get the Nobel Price and the Richest Man prize.

Power factor is another issue.
Mostly related to power company measurements and how they bill one for power.

But if You put in 2 kW of power into anything, out will come 2 kW of work or heat equal to the losses.
Otherwise it´s a scifi SpaceShunt of some kind.
Minus some limited ability to store energy in rotational stuff.

Hi,

That is incorrect, this is called power factor, it does not mean that 1kw is dissapated as heat in the VFD.

Craig

[joeavaerage]

Hi,




Craig

[UtahSmitty]

Yes you could use a VFD Drive for your spindle motor control, but you can only use one of the motor speeds so when you wire it up you will select the more used speed range and then use the VFD to change the speeds up to 120Hz for the spindle motor

When sizing the VFD Drive for a Mill and using 240v single phase power 2Hp larger then the motor Hp is a good starting point, this can depend if the VFD Drive is 3 Ph or has a single phase rating

You do not need a line reactor just a EMI power Filter is all that is need on the input power supply to the VFD Drive this should be placed close to the VFD Drive

Thanks, Mac.

I put a VFD drive on my Enco mill, and had my electrician SIL put some toroid magnets on the input legs as well as this EMI filter.

https://www.digikey.com/product-deta...SABEgLCgPD_BwE

The mill motor is 3hp 3ph and 2 speeds. The VFD powers both speeds, but there is a whine in the motor, esp. at higher speeds. The VFD was only sized to the actual motor hp, so I'm thinking I need to put a 5 hp VFD on the mill. If that doesn't solve it, then maybe it's bad motor bearings, as I don't hear any "rumbling" in the spindle when I put a stethoscope to the spindle casting.

As for the Trak Lathe, I had considered just using one of the speed ranges. In low range, I would get speeds from 60-1200 rpms at the spindle. I think this would give me the most useful range as my previous SB Heavy Ten didn't have much higher speeds than that IIRC.

I have a question about your comment about using the VFD to change speeds up to 120 Hz. Does this mean that the motor, being 60 Hz, could be run twice as fast??? It doesn't seem that that's what 120 Hz would do, but I need some clarification.

Thanks again for your input.

Smitty

[mactec54]

Thanks, Mac.

I put a VFD drive on my Enco mill, and had my electrician SIL put some toroid magnets on the input legs as well as this EMI filter.

https://www.digikey.com/product-deta...SABEgLCgPD_BwE

The mill motor is 3hp 3ph and 2 speeds. The VFD powers both speeds, but there is a whine in the motor, esp. at higher speeds. The VFD was only sized to the actual motor hp, so I'm thinking I need to put a 5 hp VFD on the mill. If that doesn't solve it, then maybe it's bad motor bearings, as I don't hear any "rumbling" in the spindle when I put a stethoscope to the spindle casting.

As for the Trak Lathe, I had considered just using one of the speed ranges. In low range, I would get speeds from 60-1200 rpms at the spindle. I think this would give me the most useful range as my previous SB Heavy Ten didn't have much higher speeds than that IIRC.

I have a question about your comment about using the VFD to change speeds up to 120 Hz. Does this mean that the motor, being 60 Hz, could be run twice as fast??? It doesn't seem that that's what 120 Hz would do, but I need some clarification.

Thanks again for your input.

Smitty

A VFD Drive can be sized for the same motor Hp when it is run on 3Ph, for single Ph use you need a higher Hp rated drive unless the VFD Drive is rated for single phase use

Yes correct the 60Hz motor can run up to twice the rated Hz this is how you control the normal speeds of a 3ph Ac motor , a reactor is only needed if you have long cables but can help with some harmonics, but a good quality EMI Power Filter will take care of the harmonics also so in most cases a Reactor is not needed

It is not good for the motor to try and use both speeds they do have a higher failure rate when run this way, if they are rated VFD Duty that is different, then you can use them this way, but most are not class F and higher which is suitable for VFD Use, so if your motor is not class F then used at a lower performance is ok for a general purpose ac 3ph motor

Changing your drive will not solve the noise you have, I guess it is setup as a second motor for the 2 speed so if it is then adjust the carrier frequency higher, for the second stage, just try it with 1 increment step at a time this may do what you need, but it also may be other programing that is not correct also, would have to know more about the motor

[mactec54]

Hi,




Craig

You have to know when it is required to use a reactor, for general VFD Drive use a high quality EMI Power Filter at around $20 to $30 will do all that is needed

The attached EMI Power Filter is all that is normally needed for general VFD Drive install / use

[UtahSmitty]

A VFD Drive can be sized for the same motor Hp when it is run on 3Ph, for single Ph use you need a higher Hp rated drive unless the VFD Drive is rated for single phase use

Yes correct the 60Hz motor can run up to twice the rated Hz this is how you control the normal speeds of a 3ph Ac motor , a reactor is only needed if you have long cables but can help with some harmonics, but a good quality EMI Power Filter will take care of the harmonics also so in most cases a Reactor is not needed

It is not good for the motor to try and use both speeds they do have a higher failure rate when run this way, if they are rated VFD Duty that is different, then you can use them this way, but most are not class F and higher which is suitable for VFD Use, so if your motor is not class F then used at a lower performance is ok for a general purpose ac 3ph motor

Changing your drive will not solve the noise you have, I guess it is setup as a second motor for the 2 speed so if it is then adjust the carrier frequency higher, for the second stage, just try it with 1 increment step at a time this may do what you need, but it also may be other programing that is not correct also, would have to know more about the motor

The motor speed on the mill is selected with a switch. When using the VFD, I change the switch setting first before starting the VFD. The VFD also starts at a low frequency setting so I just adjust the pot until it hits 60 (it doesn't go higher--not sure if that's something than can be changed in the VFD or not--the documentation is in Chinglish and fragmented).

I guess now I need to determine how to set up my lathe. I think I can live with just the lower speed setting... this will reduce the cost if I go with a RPC... What I'd like to do is use a VFD for the motor, and vary the frequency to give me some flexibility on spindle speeds, but stay in the low speed setting. Then, hook the rest of the controls up to 220 single phase power. At this point I probably need to contact a person locally that can do industrial controls and get some input on what will be required. I'm not afraid to rewire part of the control panel, but I don't know enough about contactors, transformers, etc. to want to try it without some expert assistance.

Smitty

[mactec54]

The motor speed on the mill is selected with a switch. When using the VFD, I change the switch setting first before starting the VFD. The VFD also starts at a low frequency setting so I just adjust the pot until it hits 60 (it doesn't go higher--not sure if that's something than can be changed in the VFD or not--the documentation is in Chinglish and fragmented).

I guess now I need to determine how to set up my lathe. I think I can live with just the lower speed setting... this will reduce the cost if I go with a RPC... What I'd like to do is use a VFD for the motor, and vary the frequency to give me some flexibility on spindle speeds, but stay in the low speed setting. Then, hook the rest of the controls up to 220 single phase power. At this point I probably need to contact a person locally that can do industrial controls and get some input on what will be required. I'm not afraid to rewire part of the control panel, but I don't know enough about contactors, transformers, etc. to want to try it without some expert assistance.

Smitty

Are so if he set it up correct there will be to sets of motor parameters one for the low speed and one for the high speed if he has just used one set of motor parameters then that is where the problem is

An RPC you don't want if you can do without it, which in most cases you can, if you had to go that way and have some spare cash the you would go with the Phase Perfect single phase to 3Ph they work better than anything else and you could power it right up with your 240v supply here is the link I have a large one of these running a 15Hp motor plus other equipment

https://www.phasetechnologies.com/pr.../phase-perfect

[UtahSmitty]

An RPC you don't want if you can do without it, which in most cases you can, if you had to go that way and have some spare cash the you would go with the Phase Perfect single phase to 3Ph they work better than anything else and you could power it right up with your 240v supply here is the link I have a large one of these running a 15Hp motor plus other equipment

https://www.phasetechnologies.com/pr.../phase-perfect

Thanks, Mac,

I'll check it out.

Smitty