3 phase to 1 phase - VFD vs SPC vs DPS

[C91x]

Bridgeport 1.5hp 2J variable speed Mill

I really like the simplicity of a static phase converter. It would allow me to use the original drum switch for forward and reverse. They can be had for around 80 bucks and are known to be very reliable. Problem is they only give 2/3 the power rating but at 1hp for a bridgeport I would still be fine. H&W has a solid state converter. Not exactly sure of the difference between the static and solid state??

Only experience I have with a VFD is watching one go up in smoke and try to ruin a very expensive motor in the process. They all seem to be from china if they're in my price range. I don't need the variable speed so besides soft start, the features aren't needed. They are always on unless you run a switch and the vfd controlled motor sounds different which bothers me.

I was trying to read up on Digital Phase Shifter(converter) and I can not find any information on how they work. I'm guessing that they are a VFD without the frequency adjustment. Guess this would give the same square wave as a VFD and comes with some of the issues I have with a VFD.

Here's an amazon link https://www.amazon.com/Phase-Converter-2-3HP-Motor-Digital/dp/B07F26M1TH/ref=pd_lpo_23_t_1/145-4426698-0113637?_encoding=UTF8&pd_rd_i=B07F26M1TH&pd_rd_r=ed155d74-7b2e-4117-862a-658cf73f060c&pd_rd_w=ybxGY&pd_rd_wg=HsiP5&pf_rd_p=7b36d496-f366-4631-94d3-61b87b52511b&pf_rd_r=8V0NPQX8ENP3VWEBJAC0&psc=1&refRID=8V0NPQX8ENP3VWEBJAC0


It comes down to what is harder on the motor. Running off single phase at 2/3 the power or running off a square wave? With that said I am really interested in the digital converter but just can't find any information on them.

 

[930dreamer]

You can read up in the vfd thread in the general tool section.

 

[OneOfEm]

Another option is an RPC (rotary phase converter). Configured properly, they allow for better balance between the phases and will give full HP.

 

[C91x]

You can read up in the vfd thread in the general tool section.

Thanks I'm going over it now

Another option is an RPC (rotary phase converter). Configured properly, they allow for better balance between the phases and will give full HP.

So expensive though. If I had more than one 3 phase unit I would go that route.

 

[ez-duzit]

The static phase converter will be just fine for your 1-1/2 hp motor. I've been running one for years on my ancient Index mill. Though I have a rotary phase converter mostly installed, because I have other 3-phase machines to run.

 

[wyliesdiesels]

The problem with static converters is they start the motor on simulated three phase and then once the motor is running, they drop the third leg so the motor is single phasing while running.

 

[Norcal]

The problem with static converters is they start the motor on simulated three phase and then once the motor is running, they drop the third leg so the motor is single phasing while running.

This the reason I don’t like static converters they might be ok for lightly loaded motors but they are still being single phased.

The existing drum switch could be wired to control the VFD so it had the same “feel”.

 

[nadogail]

For moderately heavy loads I would go with a rotary converter.

 

[walta]

Do not let your one bad experience with VFDs make you swear them off forever.

Most VFD installations work very well for many years without any problems.

Yes they can and do fail but very rarely in a spectacular way.

One has to wonder if your experience was a new insulation and if the real fault was in the installation and not the VFD its self.

I would think electronic variable speed would be a valuable feature to have on a mill.

Without reading the directions the Digital Phase Shifter (converter) appears to be a dubbed down VFD. I doubt it would allow you to operate switches between the shifter and the motor without damaging the shifter.


Walta

 

[C91x]

Just wanted to update this. I asked about using a rotary reverse switch with the DPS and the manufacturer stated you could. A user also replied stating that is how they had it wired up for their bridgeport and it was working.

I really wish they had more info on what the DPS actually does to get to 3 phase.

 

[nadogail]

If they told us how every product works, we would build more of them ourselves rather than pay someone else.

 

[Davefr]

Do not let your one bad experience with VFDs make you swear them off forever.

Most VFD installations work very well for many years without any problems.

Yes they can and do fail but very rarely in a spectacular way.

One has to wonder if your experience was a new insulation and if the real fault was in the installation and not the VFD its self.

I would think electronic variable speed would be a valuable feature to have on a mill.

Without reading the directions the Digital Phase Shifter (converter) appears to be a dubbed down VFD. I doubt it would allow you to operate switches between the shifter and the motor without damaging the shifter.


Walta

^^Agree!!!

There are many VFD choices out there. Buy a no name unit from Ebay and you might have issues. Buy a name brand unit with a good track record w/good documentation and you'll be fine.

I've been running my 1.5HP DP with a Teco L510 for years and it's been trouble free.

If you want to use your drum switch for reversing you can. It a simple wiring and parameter option in the VFD. If you don't like the carrier frequency sound you can change it in one parameter.

Ad a line switch and your VFD won't be always on. (but don't switch the VFD's output).

A VFD will also give you soft start, braking and a gazillion other options. Quality VFD's also have a ton of built in protections to protect themselves and the motors.

For me, a VFD would be a no brainer for a Bridgeport.

 

[TRWham]

...

I really wish they had more info on what the DPS actually does to get to 3 phase.

If it's like the Phase Perfect, it creates a 3rd waveform that, when combined with the 2 native lines, yields a correct 3 phase output. There is no voltage change, so if you input 240 V, you get 3 phase 240 V out and if you also need 120 V, you must use only one of the native lines and the incoming neutral. It cannot vary the output frequency because 2 of the lines pass straight through, so no speed control.

 

[txvwnut]

I ran a static phase convertor on my 3hp mill and it did okay but due to the power loss i switched to a VFD and haven't had any of the issues I did with the static convertor. If you have a static convertor and can find a 3ph motor that has more HP than your machine you can make an RPC using the two. The only drawback is you will have to manually start the phase generating motor or install a starter circuit. I had actually planned on doing that with mine but the motor I was given was the wrong HP and RPM.

 

[matt_i]

Strangely a static converter is an analog phase shifter....it uses a start cap to phase-shift L1 or L2 to the 3rd leg and get the motor running.

The downside to the static converter is that you have to restart the motor when shifting directions. This means holding down the mometary button that enters the start cap into the circuit in combination with selecting a direction with the drum. No plug reversing or rapid reversing if you are tapping.

The other good news is that if you get the static phase converter you can make a rotary converter just by paralleling any garden variety 3phase motor within the same HP range. Just don't attach control circuits to the generated leg...but a Bridgeport drum switch doesn't have that.

3 phase motors run just great under single phase, mindful of the mechanical output power loss. They just don't start on single phase...so unattended they will burn up because they are humming with locked rotor generating exponential internal heat. A person once had this problem where they cooked an expensive, impossible-to-replace 3-phase motor in a remote location where a person wasn't monitoring the phase-loss. And thus followed the invention of the thermomechanical overload heater section....

Edit: after I look at it I think the DPS is a miniaturized version of a contactor, start capacitor and a timer-on delay element. Functions as an automated static converter. The contactor is energized as soon as the L1, L2 input voltage is applied and no remote A1-A2 coil terminals to remote-start it.

 

[13mo]

There are many VFD choices out there. Buy a no name unit from Ebay and you might have issues. Buy a name brand unit with a good track record w/good documentation and you'll be fine.

I've been running my 1.5HP DP with a Teco L510 for years and it's been trouble free.

If you want to use your drum switch for reversing you can. It a simple wiring and parameter option in the VFD. If you don't like the carrier frequency sound you can change it in one parameter.

Ad a line switch and your VFD won't be always on. (but don't switch the VFD's output).

A VFD will also give you soft start, braking and a gazillion other options. Quality VFD's also have a ton of built in protections to protect themselves and the motors.

For me, a VFD would be a no brainer for a Bridgeport.

I will second the above. I use the same VFD as above for my 1.5 hp Clausing drill press. It cost about $200, which is not much more than a decent static converter that size would cost. The drill press came with a two-speed consequent-pole (delta/wye-wye) motor and a drum switch for fast/slow/stop. The drum switch switched the 12 lead motor from delta to wye-wye to accomplish the speed changes. I simply wired the motor to the VFD so it would run in regular delta mode (high speed) and used the drum switch to tell the VFD to run at 60 Hz on "fast," 30 Hz on "slow," and stop on "stop." This exactly replicated its original operation on 3 phase utility power. It took a little looking at the online instructions for the L510 drive and which contacts were active with the drum switch in each position, but it was extremely doable.

Typically for phase conversion:
- A rotary phase converter is going to be best if you have a bunch of 3 phase tools or you have any motors 7 1/2 hp or larger that are heavily loaded (pumps, compressors, widebelt sanders, etc.) They are expensive and cumbersome if you have a small number of motors.

- VFDs are best if you have a small number of 3 hp and under motors or specifically need the speed control, soft start, or other motor control features of the VFD. They get pricey at 5 hp and very expensive at anything that can run a 7 1/2 hp+ motor from a single-phase supply.

- Static converters are best if you have a small number of 5+ hp motors that are not heavily loaded on startup and you don't expect to run them beyond about 90% load (most woodworking tools.) They can't handle running beyond 90% load (for a good one, a poor one is 2/3 load or less) and don't cost that much less for a 1 hp unit as for a 10 hp unit.

- Solid state phase converters are similar to a VFD but without the "variable frequency" part. You get full output but they're expensive.

- Utility 3 phase is recommended if you have enough of a load that you exceed the capacity of your single-phase supply line.

 

[laser3kw]

did the OP very post back his solution?