# Digital Phase Shifters?



## ErichKeane (Mar 16, 2020)

So, I was browsing the internet the other day, and found this: https://www.amazon.com/gp/product/B07F243HLG/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

It claimed 3 phase output from 1 phase without all the VFD business.  I personally am a huge proponent of VFDs, I've owned 5 of them (typically the chinesium ones) and liked them for what they are.

However, one of mine is(spoilers, was) on my surface grinder.  The surface grinder has 3 different motors, two that power up together, and 1 that does not.  The two that power up together are Spindle + hydro pump, then a coolant pump powered up later.

It also has a pretty complicated electric panel of its own (including an outgoing 220v 1 phase plug for the coolant pump AND a 110v 1phase plug for something else), so I opted originally to wire the (greatly oversized) VFD in 'after' the switch and leave it always-on.  I ended up programming it to recover-on-fault, so that when I pressed the power button (which is on the 'wrong' side of the VFD, wired exactly as they tell you not to!) I would have to hold it to allow the VFD to 'fault' and recover and turn the 2 main motors on.

After that, everything seemingly worked acceptably. However, I did discover 1 annoying issue, the spindle motor didn't 'recover' well under resistence. I would take what should be a perfectly reasonable cut, and the spindle would slow/stop! I presumed that this was because the VFD didn't properly respond quickly enough to the increased amp load due to the other motor.

Thus, I opted to see if this "Digital Phase Shifter" would be any better.

I got it in the mail yesterday, and it seems to function alright!  It starts up perfectly on the first press of the power button, and the spindle spins at the correct RPM still.
I did a somewhat 'heavy' test cut, and it slowed a little but didn't stop!  I consider it a success.

Now, these things seem pretty expensive (more so than the VFD!), but for someone who doesn't want to deal with a VFD and already has an electrical panel/wire-up they'd like to still use, these are perhaps just the ticket!  They are very simply: 220v 1 phase (2 wires) IN, 220v 3 phase (3 wires) out!


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## JimDawson (Mar 16, 2020)

I wonder if that is the solid state version of a Phase-A-Matic.  Be interesting to put a scope on the output.


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## macardoso (Mar 16, 2020)

I would not expect that to produce sinusoidal voltage, so do not connect it to anything digital, like the mains of a 230V 3P CNC. The voltage spikes would damage the power supplies and computers. It looks like a solid state phase converter. Expect to only get 2/3 of the nameplate HP of a connected motor. 

At $200, I'd buy a basic VFD from Automation Direct. More features and more information available.


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## ErichKeane (Mar 16, 2020)

JimDawson said:


> I wonder if that is the solid state version of a Phase-A-Matic.  Be interesting to put a scope on the output.



I didn't put a voltmeter on it, however others have claimed that it gives power on all 3 legs all the time.  My understanding is that is not the case for the phase-a-matic (which IIRC is a static phase converter?).



macardoso said:


> I would not expect that to produce sinusoidal voltage, so do not connect it to anything digital, like the mains of a 230V 3P CNC. The voltage spikes would damage the power supplies and computers. It looks like a solid state phase converter. Expect to only get 2/3 of the nameplate HP of a connected motor.
> 
> At $200, I'd buy a basic VFD from Automation Direct. More features and more information available.



Others in the reviews show it puts power out on all 3 legs, which is unlike a static phase converter, right?   I would agree about getting a VFD instead, except this case (wanting the 'switch' between the VFD and motors) is explicitly listed as a 'do not do' for VFDs.


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## mksj (Mar 16, 2020)

Seems to be just a static converter with what appears to be two start and 4 run capacitors. The 3rd leg can only be measured when the motor is running "Only DPS check the voltage is the output voltage 2 phase and the output voltage 3 phase when the only motors movable". A true digital output would show voltage on the 3rd leg. There are some types of 3 phase variable speed drives that do not convert the incoming power to DC and then use PWM, they use the incoming 3 phase power and use chopper circuits for each leg. These require additional noise filtering and are only suitable for 3 phase input. Phase Perfect is the only single phase converter that I am aware of that generates just the 3rd leg from single phase input that is pretty much sinusoidal, and can drive any types of loads up to its rated specs.

Surface grinders do not do well with static converters, others that have used them in this application have noted irregular surface finish issues when using them. I would recommend an RPC in this application. In some cases with surface grinders the main drive motor is run off of a VFD, the ancillary drives are sometime DC and/or run off of a transformer that uses 2 legs of the incoming 3 phase power.


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## ErichKeane (Mar 16, 2020)

mksj said:


> Seems to be just a static converter with what appears to be two start and 4 run capacitors. The 3rd leg can only be measured when the motor is running "Only DPS check the voltage is the output voltage 2 phase and the output voltage 3 phase when the only motors movable". A true digital output would show voltage on the 3rd leg. There are some types of 3 phase variable speed drives that do not convert the incoming power to DC and then use PWM, they use the incoming 3 phase power and use chopper circuits for each leg. These require additional noise filtering and are only suitable for 3 phase input. Phase Perfect is the only single phase converter that I am aware of that generates just the 3rd leg from single phase input that is pretty much sinusoidal, and can drive any types of loads up to its rated specs.
> 
> Surface grinders do not do well with static converters, others that have used them in this application have noted irregular surface finish issues when using them. I would recommend an RPC in this application. In some cases with surface grinders the main drive motor is run off of a VFD, the ancillary drives are sometime DC and/or run off of a transformer that uses 2 legs of the incoming 3 phase power.



Well shoot, I thought the power on the 3rd leg meant it wasn't a static converter.  This is disappointing, as the VFD was doing so poorly.

I would have loved to do a RPC but they are seemingly silly-expensive.  For a case like this (~3hp total for motors), would a RPC powered by a 5HP motor be sufficient? I DO have a 5 HP 3 phase motor (out of a converted sawstop) that I could use, then I would possibly be able to just purchase the electronics...


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## benmychree (Mar 16, 2020)

I made my own RPC out of a 5 hp 3 PH motor, a static converter, and a bank of oil filled capacitors to balance the voltage on the 3rd leg, it works well enough although some motors are a little slow to start or plug reverse; I use it on my B&S Micromaster, it works fine with no issues.


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## markba633csi (Mar 16, 2020)

Nothing digital about it as far as I can see- it looks like a static phase converter with (probably) the start relay replaced by a solid state switch in the base. Maybe a little digital timer or current sensor circuit- I don't see any provision for dropout time adjustment
So you still would get only 2/3 power from any given motor.  Kind of an expensive solution vs a true VFD
Also, those caps don't look like the long-lived oil-filled types we've come to expect, so it may not last
-Mark


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## ErichKeane (Mar 16, 2020)

Do you mean something like this? https://www.ebay.com/p/1429437639?iid=191492770260&rt=nc  Can I just bolt that to my 5 HP motor and be up and running again?


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## ErichKeane (Mar 16, 2020)

markba633csi said:


> Nothing digital about it as far as I can see- it looks like a static phase converter with (probably) the start relay replaced by a solid state switch in the base.
> So you still would get only 2/3 power from any given motor.  Kind of an expensive solution vs a true VFD
> -Mark


Yep, seemingly so.  I guess I should have asked before purchasing it :/  Oh well, perhaps useful in the future for a future project (same as the VFD I removed).  Looks like I'm going to have to suck it up and and do a RPC.


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## markba633csi (Mar 16, 2020)

Well Erich you are now the official HM beta tester for that product, keep us posted


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## projectnut (Mar 16, 2020)

I would be willing to bet it's nothing more than a static phase converter.  I have a couple American Rotary brand static phase converters.  The newer ones say "Digital Static Phase Converter" under the logo.  When the static converters were discontinued the 1-3 hp models were selling for $65.00 and the 3-5 hp models were $85.00









						Digital Smart Series Static Phase Converter 3-5 HP American Rotary DS 3-5 • $68.00
					

DIGITAL SMART SERIES Static Phase Converter 3-5 HP American Rotary DS 3-5 - $68.00. FOR SALE!  DS 3-5 HP Static Phase Converter by American Rotary Use with light to moderate single loads rated between 3 and 5 HP only. After starting, 3-phase motors run at 2/3 rated horsepower. DataLink...




					picclick.com
				




The "digital" part is a small circuit board that senses when the motor has come up to speed.  When the motor reaches the rated speed the 3rd phase is no longer generated.  American Rotary no longer makes static converters under their name brand.  They're now made by a subsidiary North American Phase Converter.


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## Be_Zero_Be (Mar 16, 2020)

From one of the Reviews :

" I played with it to find out that two legs pass through and the third is generated by this box.  "

This pretty much says it is a static phase converter.


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## Reddinr (Mar 16, 2020)

Erich - I PM'd you regarding an RPC I have that I no longer need.


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## pontiac428 (Mar 16, 2020)

If you want to swap the power converter between machines, or if you're like me and don't want to gut out a beautifully wired machine with accessory motors to do a conversion, then a RPC is for you.  I got my 5hp RPC from American Rotary, IIRC it was about $700 delivered.  I think if you already have an appropriate motor you're halfway there to putting one together yourself.


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## ErichKeane (Mar 16, 2020)

pontiac428 said:


> If you want to swap the power converter between machines, or if you're like me and don't want to gut out a beautifully wired machine with accessory motors to do a conversion, then a RPC is for you.  I got my 5hp RPC from American Rotary, IIRC it was about $700 delivered.  I think if you already have an appropriate motor you're halfway there to putting one together yourself.


I have no interest in swapping (so I of a VFD for everything), but my surface grinder has an awesome motor arrangement with a really cool prewired box. Reddinr above is making me a great deal on a slightly used RPC that is admittedly oversized for my use case (10hp motor), but should get my micromaster running perfectly


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## pontiac428 (Mar 16, 2020)

Ooh, that 10 HP is future overhead!  I wish I'd bought the 10 HP rotary instead of the 5 HP.  Your feelings about your surface grinder are exactly the way I felt about my mill, I wanted to retain the original functionality, and the wiring cabinet was just too darn nice from the factory to tear apart.


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## Reddinr (Mar 16, 2020)

Erich - Just to be clear, it is RATED 5HP I think.  The 10HP motor may be over-sized for that rating though.  I think the manufacturer used what they had on hand for motors and added the capacitors/relays for the rated HP.  I bought it from a small outfit a while back.  Maybe more capacitors can upsize its rating but I don't know for sure.


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## ErichKeane (Mar 16, 2020)

Reddinr said:


> Erich - Just to be clear, it is RATED 5HP I think.  The 10HP motor may be over-sized for that rating though.  I think the manufacturer used what they had on hand for motors and added the capacitors/relays for the rated HP.  I bought it from a small outfit a while back.  Maybe more capacitors can upsize its rating but I don't know for sure.


I figured it was a 10hp motor, 5hp rated. Either way, it is likely significantly oversized for my setup. I've got 2 hp between the spindle and pump, plus another 1/2 for the coolant pump (only 1 phase).

I had originally bought a 5hp VFD since I was putting a switch in between and hoped it would be overpowered enough to not notice 

Either way, a RPC this big is a good insurance policy and will cover me in the future if I so need for a future toy


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## Reddinr (Mar 16, 2020)

I just spent the last half hour looking for the original instructions that came with it but no joy.  Connections are pretty easy though.  I remember buying it from a manufacturer in Oregon.


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## ErichKeane (Mar 21, 2020)

Reddinr hooked me up with a great RPC!  I got it hooked up and running in notime!  I ordered a switch so I can turn it off, but it fired up just right right away!

Side note:  Does ANYONE have any luck wiring  up 3ph motors the right way 1st time?  I think I'm 0 for about 8 now.


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## Mdm.motosports (May 20, 2020)

I have been using this on a 5 hp mazak mate. It works wonderful so far. It is not a static phase converter. It does generate a 3rd leg. Obviously the third leg is squeezed in at 90 hertz from the other legs but, thats the same as a
Rotary. Been using for almost a year. Hobby shop. 


Sent from my iPhone using Tapatalk


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## matthewsx (May 20, 2020)

I guess if you wanted a 

"Semi-permanent life time"

That device would be perfect....


john


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## WyldStyl3 (Sep 9, 2022)

So what was the consensus here?  I thought he said it was working fine in the original post.  Are these things not good to use?  I just got a 3ph mill and have been trying to find the best way to get it to 1ph.  I came across these on amazon and they're cheaper than VFDs.


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## ErichKeane (Sep 9, 2022)

They are just cheap solid state static phase converters, with all the downsides that come with those (plus a square wave or oscillating wave from the electronics).  They are a great cheap solution for 1-3ph, if 1/2 power is acceptable.

In my case it was fine on the machines I was running off of, but for a couple of reasons, I switched to RPCs or VFDs for everything.


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