# Short Term, Budget Friendly, 3 Phase Options



## MyLilMule (Dec 1, 2021)

I have a Series 1, 2HP Bridgeport with a variable speed head on which I am just beginning the restoration.

I currently do not have 3 phase power in my workshop. The plan WAS to get a 5HP rotary phase converter from American Rotary (my preferred manufacturer). However, I am looking for some possible short term, more budget friendly alternatives.

Reason being, I do not want to invest $800 in a phase converter, to find that in a year, I add a 5HP lathe to the mix and end up needing a bigger phase converter. So to bide my time until I make that decision one way or another, I want to find if there are any alternatives that are MUCH less expensive.

I'm open to ideas that will let me run the mill, even at reduced HP, for the short term (1 year) until I have either decided against adding a bigger lathe or not, at which time, I'll get an appropriately sized RPC.

If the answer is "no" then I'll bit the bullet and get the American Rotary unit.


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## DAT510 (Dec 1, 2021)

Would you ever be running the mill and lathe at the same time?  I personally never have with my machines... If not, I'd just get a phase converter that meets the needs of the highest HP machine you expect to have and use it for both.


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## MrWhoopee (Dec 1, 2021)

Static Phase Converter.








						SCM03-1 - 3 Hp HD SCM series Static phase converter
					





					phaseconverterusa.com
				




Like you, I bought one to fill the gap until I got my 7.5 hp rotary. Once I got my RPC, I quickly grew tired of the whine. Then my wife saw the electric bill. The RPC is in mothballs and I've been using the SPC ever since.

edit: Anyone want to buy a 7.5 hp RPC?


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## woodchucker (Dec 1, 2021)

I picked up a rotary phase converter on facebook market place. I don't do face book, but my neighbor keeps an eye out for equipment for me.
It's a cedarburg. I paid $75, no capacitors.. for my surface grinder it's been great.

Now, I am not saying go out and buy new, it is $950 new.

but since you are restoring, look around you have time... and maybe the machinist gods will be friendly to you.


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## talvare (Dec 1, 2021)

Building your own RPC can be much more economical than purchasing a commercially made unit. It is not that difficult to build one and there is a lot of good information on this forum to help you along.
Food for thought.
Ted


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## MyLilMule (Dec 1, 2021)

MrWhoopee said:


> Static Phase Converter.
> 
> 
> 
> ...


That looks interesting. I'll have to do some research on it.


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## MyLilMule (Dec 1, 2021)

talvare said:


> Building your own RPC can be much more economical than purchasing a commercially made unit. It is not that difficult to build one and there is a lot of good information on this forum to help you along.
> Food for thought.
> Ted


Not really interested in that option. Yes, I am certain I could build one. But I would rather spend my time rebuilding a vintage piece of machinery and using it, than this. I've also spend decades building my own computers, but as age and wisdom have creeped in over the years, now I just buy Apple Macbooks.


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## mksj (Dec 1, 2021)

So several options as outlined above, static converter is inexpensive for short term, you loose some Hp. You can buy an RPC box for not much more and then just find a motor (1750 RPM) locally and save about 2/3rds the cost of a new RPC. You just hook-up the 3 phase motor. A 5 Hp RPC will run a 2 Hp 3 phase motor, so somewhat limited for all the work. There are inexpensive VFD's (2 Hp) that could be used, and just use a simple switch to control the inputs for the run command. They can be had for as little as $100 for a generic  brand with cryptic instructions sold on Amazon/eBay,  or something like a Teco 2 or 3 Hp single phase input L510-202-H1-U will run around $200, the 3 Hp typically is $275 but link below is $217. The VFD's are pretty simple to setup, direct connect to the motor and in your case leave it a 60 Hz and use the mechanical Reeves drive. Check availability/inventory of the drives before doing on-line purchase, many vendors are out of stock and often do not have a due date for restocking. The drives have also gone up in price about 30% from 2-3 years ago.









						L510-203-H1-U TECO 3 HP 230V 1-Phase Input 10.5 Drive Amps C
					





					shop.powerandcontrol.com
				





			https://www.amazon.com/LAPOND-Inverter-Professional-Frequency-VFD-2-2KW/dp/B01DKJWM6W/ref=sr_1_22
		









						CP-7 Pro-Line 7.5HP Rotary Phase Converter Control Panel - Loaded with Features  | eBay
					

Add your own motor and make a rotary phase converter. Rotary Phase Converters. 7.5HP Pro-Line Rotary Phase Converter CP-7. Static Phase Converters. Digital Phase Converters. Easy / Light Motor Loads - up to 5HP.



					www.ebay.com


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## NCjeeper (Dec 1, 2021)

I would go with a static converter then. You will be only getting about 2/3rds the power out of your motor this way, but this will buy you some time until you decide on what size RPC to go with.


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## Technical Ted (Dec 1, 2021)

I have a vari-speed 2HP Bridgeport at well. I run mine from a VFD and am glad I do. There are many times when hi range is a little too fast and rather than switching into low range I simply slow down the VFD. To be honest, I can't even remember the last time I dropped into low range...

Another consideration is you might end up with a flat belt drive lathe, like a South Bend, and I REALLY love having the VFD on mine! It really comes in handy being able to tweak the speed on the fly. I have a single phase motor on my larger SB 15" and it's not nearly as nice to run. 

Just a couple of things to consider before you make a decision.

Ted


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## Winegrower (Dec 1, 2021)

Help me with this, folks!   This issue of only getting 2/3 the power is overblown, in my opinion.   You get all the power the equipment asks for, up until it needs more than 2/3 power.   What happens beyond that is a bit unclear, seems like some winding currents would maybe go beyond design ratings for a bit, but really, what is in the phase converter that's a problem?...the power comes from the normal single phase line, that really doesn't have a HP limit, if you've sized the wire and breaker correctly.   

I power my Bridgeport mill, 1.5HP, the Takisawa lathe, 3HP and the Kalamazoo saw, ? HP from one 1 to 3 HP phase converter.   I literally have never experienced anything that seemed like a power limitation.


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## MyLilMule (Dec 1, 2021)

Technical Ted said:


> I have a vari-speed 2HP Bridgeport at well. I run mine from a VFD and am glad I do. There are many times when hi range is a little too fast and rather than switching into low range I simply slow down the VFD. To be honest, I can't even remember the last time I dropped into low range...
> 
> Another consideration is you might end up with a flat belt drive lathe, like a South Bend, and I REALLY love having the VFD on mine! It really comes in handy being able to tweak the speed on the fly. I have a single phase motor on my larger SB 15" and it's not nearly as nice to run.
> 
> ...


I have a flat belt South Bend 13", but it was converted to single phase 220 by the previous owner. What I am hoping to find is a replacement some day for it, something like a nice Monarch (not a 10ee), Pratt & Whitney, LeBlonde, etc. - but those are future plans.

What VFD are you using?


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## MyLilMule (Dec 1, 2021)

Winegrower said:


> Help me with this, folks!   This issue of only getting 2/3 the power is overblown, in my opinion.   You get all the power the equipment asks for, up until it needs more than 2/3 power.   What happens beyond that is a bit unclear, seems like some winding currents would maybe go beyond design ratings for a bit, but really, what is in the phase converter that's a problem?...the power comes from the normal single phase line, that really doesn't have a HP limit, if you've sized the wire and breaker correctly.
> 
> I power my Bridgeport mill, 1.5HP, the Takisawa lathe, 3HP and the Kalamazoo saw, ? HP from one 1 to 3 HP phase converter.   I literally have never experienced anything that seemed like a power limitation.


Perhaps you are correct. But I would rather have it and not need it (if I can afford it) than need it and not have it.


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## MrWhoopee (Dec 1, 2021)

Winegrower said:


> Help me with this, folks!   This issue of only getting 2/3 the power is overblown, in my opinion.   You get all the power the equipment asks for, up until it needs more than 2/3 power.   What happens beyond that is a bit unclear, seems like some winding currents would maybe go beyond design ratings for a bit, but really, what is in the phase converter that's a problem?...the power comes from the normal single phase line, that really doesn't have a HP limit, if you've sized the wire and breaker correctly.
> 
> I power my Bridgeport mill, 1.5HP, the Takisawa lathe, 3HP and the Kalamazoo saw, ? HP from one 1 to 3 HP phase converter.   I literally have never experienced anything that seemed like a power limitation.


I too have never experienced a situation where I felt that my 2 hp mill was not delivering enough power. I'm sure that, if you had two equal machines side-by-side, one powered by an RPC and the other by an SPC, you might be able to find a point where the one with the RPC would pull a cut that the SPC powered (actually just started) would not. 

For reasons that have not been determined, my 1 hp SB Heavy 10 will not start properly with the SPC. When I need the lathe, I disengage the spindle on the mill and start it. The mill functions as an RPC and I can use the lathe normally, including instant reversing. Once the mill is started, the SPC does not come into play. Instant reversing is something that does not function properly with an SPC. When power tapping on the mill, I have to stop the spindle before reversing. Otherwise it continues to rotate in the same direction.


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## JRaut (Dec 1, 2021)

I use this VFD ($90) for my 1.5 HP Bridgeport.


			https://www.amazon.com/gp/product/B01DKJWM62/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
		


That model claims to work for up to 2hp, but there is a step-up model for an extra $10 that'll work for 3hp

I don't use any of the available speed-change controls for it, just use it to get 3-phase.

Couldn't be happier with my purchase.

Installation / setup was easy. I locked it in a cabinet behind my Bridgeport 2.5 years ago and haven't so much as looked at it since.


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## NCjeeper (Dec 1, 2021)

Taken from the wolf automation website.



Digital Static Phase Converters​These straightforward units start your application with a 3 phase load but then switch to single phase power.
This is done through circuitry disconnecting after start-up and subsequently limits the load to about 2/3 of its rated capacity. This does effect your selection depending on how you intend on running your motor. Applications which require a high torque start-ups but not consistently high HP, such as drill presses, milling machines, and table saws, work best with Digital Static Phase Converters.


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## projectnut (Dec 1, 2021)

I have a 1 1/2 HP Bridgeport that's been running on a static converter for nearly 20 years.  Like others I've never noticed a lack of power.  There have been weeks it's run between 40 and 60 hours or more with no ill effects.  Even on the longest running weeks the motor is barely warm to the touch.  This machine is running on a Phase A Matic PAM 300HD.  It cost about $125.00 new.  Today they run a little over $230.00

I have 3 other machines running on static converters.  A Sheldon MW-56-P lathe (2hp), a Racine 66W2 power hacksaw (1.5 hp), and a Black Diamond drill grinder (1/3hp).  The Sheldon and the Racine are using American Rotary brand static converters.  The Black Diamond is on a North America brand static converter.

I have been very happy with all the converters.  The American Rotary's cost about $80.00 new and carry the same lifetime guarantee as the Phase A Matic.  American Rotary quit building static converters under their name about 5 years ago.  I didn't realize it at the time, but I believe they had already discontinued production when I ordered the one for my lathe.  It should have dawned on me that they were liquidating inventory since it only cost $60.00 with free shipping. They bought out North America at the time and transferred all the static converter business to that name.

I have the same model on my power hacksaw as NCjeeper is using on his mill.  I would love to find another for a future machine, but since they haven't been made for several years it's unlikely, I'll find one at a good price


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## Bi11Hudson (Dec 1, 2021)

Technical Ted said:


> I have a vari-speed 2HP Bridgeport at well. I run mine from a VFD and am glad I do. There are many times when hi range is a little too fast and rather than switching into low range I simply slow down the VFD. To be honest, I can't even remember the last time I dropped into low range...


At the bottom line, a Rotary Converter is a three phase motor with proper [for the size] capacitors. And possibly a little extra for a "kicker" to get it started. I personally avoid any 3 phase equipment so that I am not dependant on another contraption to run my shop. With that said, I am generally in favor of 3 phase *if *it is readily available. A 3 phase motor can be run simply by adding capacitance to generate the third leg. That is all a Rotary Converter does. Plus being pre wired and with a good enclosure. And sometimes other "bells and whistles".

A "Variable Frequency Drive", aka a VFD, converts the incoming line to DC and electronically generates a 3 phase output. Depending on the quality of the VFD, this can vary from a (near) square wave to a (near) sinusoidal output. A good quality VFD will naturally be more expensive than a low end drive. But price is not necessarily a good indication of quality. There are some limitations to a VFD, not the least that one per motor is required. But on the up side, speed of that motor can be easily varied from 50% to 150% without noticable loss of power from the motor. When all the drive is powering is a reactive load (motor), even a square wave is magnetically rounded off.

If the deciding factor is cost alone, try a few motor starting capacitors from one side of the line to generate the third leg. If more $$ is available, I personally would recommend a VFD over a Rotary simply for the variable speed aspect. There are down sides to any "fix", it is a "band aid" by another name. From bringing in 3 phase power to the lowest conversion, there will be a cost. The individual must make the final call as to which cost is the most acceptable. 

.


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## MyLilMule (Dec 1, 2021)

Bi11Hudson said:


> At the bottom line, a Rotary Converter is a three phase motor with proper [for the size] capacitors. And possibly a little extra for a "kicker" to get it started. I personally avoid any 3 phase equipment so that I am not dependant on another contraption to run my shop. With that said, I am generally in favor of 3 phase *if *it is readily available. A 3 phase motor can be run simply by adding capacitance to generate the third leg. That is all a Rotary Converter does. Plus being pre wired and with a good enclosure. And sometimes other "bells and whistles".


I think this is an oversimplification. A good quality rotary phase converter generates the third leg because the "motor" isn't a motor, but an induction generator. It's not just a motor and some capacitors. Capacitors don't generate anything. They store potential. The only reason they "work" is that the stored potential in the capacitor simulates a third leg getting the motor started. Once the motor is started, inertia takes over and it can be run on just the two legs. The third is essentially dead since there is never enough potential in the capacitor anymore. It's all going to the other two legs. I know my electronics - by no means an electrical engineer, although that was my major in college before dropping out to join the military.

Also, some would argue, although I have not seen any evidence of it being fact, but can understandably see the possibility, is that a 3 phase motor, when properly powered by 3 phase power, will be more stable, especially at high torque, resulting in a cleaner surface finish.

Regardless, I have no desire, even though capable, of building an RPC or just throwing some capacitors on high voltage lines. I am willing to give the VFD or SPC a try, especially if it's affordable, and not feel I wasted my time or money.


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## Shootymacshootface (Dec 1, 2021)

My 2 hp Bridgeport has stalled several times while hogging with a 3" face mill and with the larger S&D drill bits. It is powered with a 5hp rpc. I wouldn't consider powering it with a static converter.


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## Bi11Hudson (Dec 1, 2021)

I am not going to get into the electrical theory involved, but my statement above is fairly accurate. A true generator must be spun at 3600 or 1800 RPM. Or some other specific speed. It can only be generated from a power line throuh the use of a synchronous motor or a DC motor with *very* solid speed control. Do a little more research. . . 
.


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## matthewsx (Dec 1, 2021)

Static converters have also worked fine for me. If you want a rotary converter later it's just a matter of wiring in a suitable 3 phase motor, you already have the switching and caps in the static. Buy a suitable size static converter and keep your eyes out for an inexpensive 3 phase motor for if you want the rotary "true 3 phase" later.

That, or just move to a place where 3 phase is available.

Or, buy a military surplus 3 phase generator.

John


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## tq60 (Dec 1, 2021)

We have a static converter on the 7.5 hp lathe and with it being gear head with oil on a cold day it cannot handle just the spindle at high speed, not that fast as 16 inch.

The 1 hp bridgeport has a 1 hp VFD, was originally the vari-speed but previous owner in pro shop with 3 phase converted to a single pulley drive with the 1 hp vfd as he did not need to de-rate, works fine unless we need torque then back gear required.

The SB 14.5 is 2 hp with 3 hp VFD, in middle belted speeds plenty of torque at very low RPM, in Back gear can do MPR.. 

The car lift has a 5 hp rotary that was very noisy until we added isolation pads, works well.

Given you have 2 hp motor and need fast and cheap the static will still give more than 1 hp and the variable speed will give good torque and back gear for more.

They are simple to connect and CHEAP.

Rotary adds noise and operating expense but less hp losses.

Static are simple and cheap at the expense of output power.

Both allow simple direct connection of factory power supplies with minimal issues other than keeping control power on a real leg and not manufactured.

The rotary allows one device to be used for many, spc too maybe but not suggested.

Vfd is married to the machine and is usually best outcome but skills to install and front end expense usually is a show stopper.

That will get you going and you can then save for a VFD.

We like Allen Bradley 1300 series as the mill came with one and eBay for other at 200.00 but harder to find and now older.

RPC are noisy and expensive to just have running

Sent from my SM-G781V using Tapatalk


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## tq60 (Dec 1, 2021)

Shootymacshootface said:


> My 2 hp Bridgeport has stalled several times while hogging with a 3" face mill and with the larger S&D drill bits. It is powered with a 5hp rpc. I wouldn't consider powering it with a static converter.


That heavy of cut requires back gear and maybe more than 2 hp.

Out 1 hp can do well but only in back gear.

For 1/2 twist drill we like slow speed but with the single speed internals back gear required.

Sent from my SM-G781V using Tapatalk


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## graham-xrf (Dec 2, 2021)

Something to consider about delivering power to 3-phase motors. They can be wired in "star", also called "Y" mode, which is a series connection, or wired in "delta", which is a parallel connection mode. The delta mode suits a lower phase voltage, OR, if the voltage is left alone, delivers 1.73 x more power.

Common US electrical supplies are usually 2 phases 110V or 120V, with a neutral in the middle. You can get 220V or 240V for higher power stuff by connecting across both phases, and this is truly best for running machinery.

So come to all manner of VFDs and phase converters. The take the input voltage (say 220VAC, and rectify it, to make a DC bus, in this case approximately 311V, probably filtered to about 300V on load, and then use all the smart electronics to make you a new artificial AC output to drive a motor. This can be single phase, but crucially, can also be three-phase.

So - though I have not done the math all the way down to the final poweer, a three-phase motor, driven off convertor electronics, with a motor wired in delta, can likely give you the power you need.


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## Winegrower (Dec 2, 2021)

graham-xrf said:


> So - though I have not done the math all the way down to the final poweer, a three-phase motor, driven off convertor electronics, with a motor wired in delta, can likely give you the power you need.


Yes indeed, given that the VFD is sized correctly.   Wye or delta doesn’t matter, a motor rating is what’s important.
The difficulty of using a VFD is that the normal equipment controls must now be rewired or added to go to the VFD as control inputs…thinking forward/reverse, speed control, etc.


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## graham-xrf (Dec 2, 2021)

Winegrower said:


> Yes indeed, given that the VFD is sized correctly.   Wye or delta doesn’t matter, a motor rating is what’s important.
> The difficulty of using a VFD is that the normal equipment controls must now be rewired or added to go to the VFD as control inputs…thinking forward/reverse, speed control, etc.


Yes indeed, you are right. One might sometimes get up to changing wye or delta when it is about matching to the motor capability. Changing to delta, for example, might be overworking a motor that was already at it's limit.  If starting from 220V or 240V input to the drive, machine 3-phase motors in wye configuration would be unable to deliver full power using a artificial PWM switched 3-Phase, unless changed to delta configuration. This takes advantage of the motor drive's ability to deliver the current, even starting from a lower bus voltage.

Regarding the controls. For those who want the existing buttons and knobs to do exactly what they did before, it is usually possible to make their contacts work as before, by using their contacts to deliver low voltage or groundings as logic inputs to motor controllers. This can be 24V, usually DC, but sometimes can be 24VAC from a step-down transformer, or sometimes 5VDC. Most logic inputs are already biased, only needing to be grounded by a switch in it's new role.

_[*EDIT: Warning!  DO NOT*  use existing switches to try to swap two output phases to the motor wiring as way of "reversing" the motor. 
This means do not connect the drive to the wires where the power "used to go", via contactors and switches.
The cable from drive electronics U, V, W to motor must be direct, and have nothing else else in it's way.
Disconnecting and reversing a controlled motor in full flight is a violent abuse of the electronics, likely to result in an overcurrent fault, if not simply ending up damaged and unresponsive forever!  You can easily command super-sweet reverse from the same switches, but let the internal software do it for you!]_

There are, of course, all the new standard features, like variable speed control to faster and slower than before. There is acceleration up to to speed soft start, and deceleration to stop in a controlled way. This can have it do extremely fast braking, yet to a smooth, non-violent stop, assisted by a braking resistor that one can usually provide, if not already built-in. Going from full forward to full reverse in a controlled way without over-stressing anything becomes easy. Either add in the switches/knobs for the new features, while retaining what the original switches do, or go for an entirely new control arrangement.

One thing to consider well is how low speed can you go while still at full torque. Modern switched electronics with current sensing can deliver huge torques into permanent magnet motors, even at stall, but if the plan is to keep a original squirrel-cage induction motor, there may be limits to it's compatibility with being driven by a switch mode contrived artificial AC. The way the rotor becomes magnetic works better if it is at least allowed to spin some. If the machine has belts or gears that were used for speed changes, choose one that has a lower gearing, to have the motor reasonably spinning, even if the VFD has slowed the spindle down to slower than you ever saw before.

At the other end, making a drive "go faster" than the original phase rotation speed is also possible, but keep it sane. Don't go exploring motor speeds that will mess up on the design limits of bearings and other bits. Usually, VFDs that are sold as VFDs intended to work existing machine motors are already default configured to suit the norms.

Finally, regarding the connecting up. Appreciate that this is no longer a sweet sine-wave AC going to the motor. It is a high audio frequency switched-carrier, pulse-width modulated horror, full of high frequency transients. This is fast switching of high currents! Use the screened cable, if possible one with symmetric layup conductors. If there are common-mode suppression ferrite toroids included, do not forget to mount them on the cable. Connect exactly as specified in the manual. Just because "the motor turns", is not enough! If it shows the screen grounded only at a provided point on the drive, then only do it there, and nowhere else. If the motor squeals, the carrier frequency parameter is set too low. Set as high as you can, keeping in mind the length of the cable. Normally done from a configuration parameter, I have found 8KHz, or better, 12 KHz or so makes them go quiet, even on a 25m run. Getting the screening wrong can upset it's controls. It can mess up other computer-based stuff on the same power, and cause the father and mother of RF interference to everything!


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