Phase converters

[motofool33]

So I have 220v(single phase), and 110v in the shop. And I've been eyeing some 3 phase stuff like air compressor ' s in the 7 - 10 hp range. Some used mills and sturdy wheel grinders. Welders etc.

So my question is where do you guys find good prices on these phase converters and what should I look for when getting one.

Next on the air compressor what would be more cost effective replace the 3 phase motor with a single phase or a phase converter?

 

[Techie1961]

I have found a few phase converters (roto phase) on Kijiji but I think that Craigslist is more popular in your area. Just keep checking. If you can go with a phase converter, I would recommend it. Single phase motors aren't as dependable due to the starting switch and capacitors in the motor.

 

[P.Allan]

Phase converters are very easy to build. All you need is a 3 phase motor and a bunch of capacitors. There is just a ton of info about building them on the internet. Lot cheaper than buying one.

 

[404]

As P.Allan says build one. The capacitors to use are the metal can oval (sometimes round) ones that are for motor run. Do not use the motor start caps (black plastic cover) in the part of the circuit where the caps are connected to the motor all the time. Some caps are here.

http://www.surpluscenter.com/shop.axd/Search?keywords=capacitor

I ended up using 60 microfarad of combined caps 440 volt on my 220 converter. Idler motor is a baldor 1800 rpm 2 horse.

The converter starts rotating by itself when power is applied, no fuss. I originally had a more complicated circuit with an additional start cap, and a soft start circuit but the added complexity and occasional relay wearing out was not worth it.

Regards,
404

 

[404]

If I were to build another converter today i would buy 2 of these

http://www.surpluscenter.com/Electr...VAC-OVAL-DUAL-RATED-RUN-CAPACITOR-22-1230.axd

use the 30 mfd side on each and ignore the 7.5 mfd side.

Regards,
404

 

[WhoWhatNow]

You may want to think about what equipment you run on 3ph vs. single. I love the VFD on my mill and will be putting one on my lathe shortly. The advantages are variable speed w/o pulleys, braking and cost.

For an air compressor my understanding is that you will need a rpc that is at least 2-3X as big as your motor. It may be cheaper and easier to simply go with a 5 or 7.5 hp single phase motor.

I also haven't seen much about the feasibility of running a welder on a rpc. Some say you can't. An engine driven welder may be a better option if you need lots of power.

Someone on this board pointed out that grinders are so cheap and plentiful that unless you need a huge 10-12" grinder there is rarely a good reason to run a 3ph with a rpc.

 

[scw1991]

It might be more economical to consider the TECO FM50 or TECO CV7300 series VFD to run 3ph motors off of 1ph power. I think it would be cost prohibitive to try and run a 3ph motor any larger than about 3 horsepower.

 

[404]

The miller CP200 is a 3 ph welder that can be converted to single ph.

http://www.practicalmachinist.com/v...ler-cp200-converted-240v-single-phase-199832/

 

[ddawg16]

If you are looking to buy a compressor, I would not go 3ph knowing I would also need a phase converter. You're going to need more power to run both the phase converter and compressor vs just running the compressor off 240vac single phase.

It just ends up adding more complexity than needed.

 

[930dreamer]

Rotary phase converters are pretty simple to build, I've put together a few and I have a sixth grade education. I currently run a 10hp converter using 6ga wire and a 50amp circuit with no capacitors. Shop equipment is a 5hp champion compressor, two grinders and a test circuit for new three phase finds.

 

[motofool33]

I hear you ddawg,

Just hard to swallow the 6k for some of the single phase nice compressors when the 3 phase ones come up for 750$-1000$ for something that would last me 30 years.
Might be better to just swap the motor out then phase convert the air compressor.

On the grinder this is what I meant by big grinder
http://houston.craigslist.org/tls/4736345238.html

Didn't real use the welders were that picky with phase converters I'll scrap that idea I have a nice 220 mig stick n spool gun combo now.

 

[930dreamer]

I hear you ddawg,

Just hard to swallow the 6k for some of the single phase nice compressors when the 3 phase ones come up for 750$-1000$ for something that would last me 30 years.
Might be better to just swap the motor out then phase convert the air compressor.

On the grinder this is what I meant by big grinder
http://houston.craigslist.org/tls/4736345238.html

Didn't real use the welders were that picky with phase converters I'll scrap that idea I have a nice 220 mig stick n spool gun combo now.

That's a great looking monster grinder. What size is your shop panel? Build a converter just to say you built one and see where it takes you.

 

[A_Pmech]

I hear you ddawg,

Just hard to swallow the 6k for some of the single phase nice compressors when the 3 phase ones come up for 750$-1000$ for something that would last me 30 years.
Might be better to just swap the motor out then phase convert the air compressor.

On the grinder this is what I meant by big grinder
http://houston.craigslist.org/tls/4736345238.html

Didn't real use the welders were that picky with phase converters I'll scrap that idea I have a nice 220 mig stick n spool gun combo now.

A right and proper grinder.

For an air compressor, it's fairly simple to make an automatic starting circuit for a phase converter. When the compressor calls for air, it closes the phase converter circuit, waits for the phase converter to come up to speed and places the air compressor load on the line.

However, VFD's are probably the quickest way to power a large 3-phase compressor. I have a 25HP compressor that will be getting a VFD shortly. "phase converter" VFD's are available to at least 50HP. They're just 3-phase VFD's with larger filter capacitors and rectifiers. The upside of this arrangement is they offer soft starting capability, which can be helpful in residential areas.

Hitachi also publishes a white paper on using 3-phase VFS's on single - phase input. They are more expensive than "converter" drives new, but inexpensive used.

 

[Steve from Socal]

I agree with Deputy John; a single phase compressor makes the most sense. Three phase motors have qualities that are preferred for machine tools and are less expensive per HP generally but, the starting load on a compressor is a major issue with a phase converter. Practically you are looking at 7.5 HP as the largest single phase compressors, I have seen several dual pump single phase compressors to get higher CFM rates.

While rotary converters are very effective they are another layer of complexity and, the do consume power even idling. Rotary converter starting a motor under load need 2-3 times the HP of the motor they start. A 15-20 HP rotary is going to require some significant power, rather heavy wiring and controls and, depending on your electrical service above the single breaker limit. The power into the rotary will be 1.73 times the rated amps used on three phase. A 20 hp rotary will need an 85 amp circuit.

Steve

 

[ddawg16]

One other point...

When you look at the cost of the phase converter....and you feel you really need the power of a 3ph motor, then before spending money, I'd be contacting the PoCo to see what it would take to get 480Vac 3ph to the building. Once you have it, it opens up a whole new set of options.

For some people, 3ph is not an option. But if it is......

What I don't know is if the PoCo charges more for a 3ph connection.

 

[ez-duzit]

Change the compressor motor to 1 phase.

Using a VFD limits a motor's power to about 2/3 of its rating--you cannot get full power. Do not use one on machines that start or run under heavy loads, like disc sanders, compressors, etc.

 

[930dreamer]

Change the compressor motor to 1 phase.

Using a VFD limits a motor's power to about 2/3 of its rating--you cannot get full power. Do not use one on machines that start or run under heavy loads, like disc sanders, compressors, etc.

Not correct.

" Although you must derate a VFD rated for three phase input as discussed above, when you do that, the actual mechanical power delivered by your saw will be 100% of nameplate on a VFD".

 

[motofool33]

I think 3 phase is available it is a commercial building but all tenants in it currently do not have it. The pole is about 15 feet from my panel and the is mounted to my unit. I asked the contractor who built the buildings but never heard back.

 

[ez-duzit]

930--wrong.

 

[logixjock]

Change the compressor motor to 1 phase.

Using a VFD limits a motor's power to about 2/3 of its rating--you cannot get full power. Do not use one on machines that start or run under heavy loads, like disc sanders, compressors, etc.

You're thinking of a STATIC phase converter, a properly tuned and sized rotary converter will very nearly give you full power. If your unloader is working properly a well tuned 10HP rotary will have no problem starting a 7.5HP compressor.

I haven't tried any of the newer inverter based welders on a rotary, but the older welders work very well with one.

This is all based on experience, not something I read 3rd or 4th hand on the internet. I don't have the numbers from the tuning session on my last 10HP rotary but I remember the idling current was very low. I seem to remember figuring the cost for the customer and it worked out to less than $50 a year for 520 hours of idling.

I'll be starting another 5HP rotary build that will be running a small round column mill in a few weeks, I'll try to document it here.

 

[ez-duzit]

A rotary phase converter can deliver nearly 100% of rated motor power. A VFD or static phase converter provides about 2/3 of rated power.

 

[logixjock]

A rotary phase converter can deliver nearly 100% of rated motor power. A VFD or static phase converter provides about 2/3 of rated power.

A VFD designed to run on single phase input will give you full power, a VFD designed to run on 3 phase input running with single phase input with the phase loss detection fault turned off will give you 2/3 rated power.

 

[A_Pmech]

A VFD will provide full rated power and beyond, if the vfd is set up to allow it. The power quality to the motor is better than what comes off the power company's lines. They will also start incredibly hard starting loads far beyond what can be started across the line. An example being very large regenerative blowers with start cycles measured in minutes.

 

[A_Pmech]

A VFD designed to run on single phase input will give you full power, a VFD designed to run on 3 phase input running with single phase input with the phase loss detection fault turned off will give you 2/3 rated power.

A 3-phase VFD on 1 phase will provide full rated power. However, it should be de-rated as the rectifier end will not handle full power from a single-phase source.

 

[ddawg16]

A rotary phase converter can deliver nearly 100% of rated motor power. A VFD or static phase converter provides about 2/3 of rated power.

Not exactly accurate....

http://www.kayind.com/tech_center/FAQ.htm

How efficient are phase converters?

Extremely efficient. Losses are generally less than 15% and usually under 10%. One must remember, however, that only one third of the total energy consumed by the load actually passes through the converter. Therefore, the total loss of the converter system is 15% of 33% or about 5% of all the energy consumed. That translates to 95% overall efficiency.

 

[ez-duzit]

16--that's for a rotary phase converter.

 

[toplessHO]

can someone please direct me to the proper tuning of a 3ph 3hp radial arm saw to run on single phase.
When I got it 35+ yrs ago it had a 3ph motor that was used as a phase converter but that has long since been lost. I do have a couple 5hp 3ph motors and lots of oil can caps.

 

[A_Pmech]

can someone please direct me to the proper tuning of a 3ph 3hp radial arm saw to run on single phase.
When I got it 35+ yrs ago it had a 3ph motor that was used as a phase converter but that has long since been lost. I do have a couple 5hp 3ph motors and lots of oil can caps.

Check out the "Fitz William" plans available on Practical Machinist.

 

[logixjock]

Check out the "Fitz William" plans available on Practical Machinist.

That's what I've based my designs on. Works very well.

 

[larry_g]

Check out the "Fitz William" plans available on Practical Machinist.

its Fitch Williams

http://www.practicalmachinist.com/v...nverter-design-balancing-instructions-101882/

lg
no neat sig line

 

[toplessHO]

thank you all Ive got some studying to do

 

[toplessHO]

does the idler motor have to match the HP of the driven or (work) motor,or can I use the 5hp 3ph idler for a 3hp machine?

 

[logixjock]

Retracted

 

[logixjock]

does the idler motor have to match the HP of the driven or (work) motor,or can I use the 5hp 3ph idler for a 3hp machine?

That would be a good match if you tune it well.

 

[ez-duzit]

does the idler motor have to match the HP of the driven or (work) motor,or can I use the 5hp 3ph idler for a 3hp machine?

It depends on the machine. An air compressor or bandsaw, for example, may require an idler of perhaps 1.5-2.5 X its own motor rating.

 

[toplessHO]

its a large(14 inch) DeWalt radial arm saw.
Cast iron everything and built like a tank.

 

[930dreamer]

its a large(14 inch) DeWalt radial arm saw.
Cast iron everything and built like a tank.

I have a 7.5hp RAS that I can start with my 10hp RPC.

 

[A_Pmech]

its Fitch Williams

http://www.practicalmachinist.com/v...nverter-design-balancing-instructions-101882/

lg
no neat sig line

Thank you Larry! I should know that... I built a 10 HP per his plans!

 

[930dreamer]

A right and proper grinder.

For an air compressor, it's fairly simple to make an automatic starting circuit for a phase converter. When the compressor calls for air, it closes the phase converter circuit, waits for the phase converter to come up to speed and places the air compressor load on the line.

However, VFD's are probably the quickest way to power a large 3-phase compressor. I have a 25HP compressor that will be getting a VFD shortly. "phase converter" VFD's are available to at least 50HP. They're just 3-phase VFD's with larger filter capacitors and rectifiers. The upside of this arrangement is they offer soft starting capability, which can be helpful in residential areas.

Hitachi also publishes a white paper on using 3-phase VFS's on single - phase input. They are more expensive than "converter" drives new, but inexpensive used.

Where are you sourcing these large vfd's from?

 

[Packard V8]

Yes! Where? How much? I've got a 25hp Kaeser rotary screw compressor I'd love to run off single phase 220V.

jack vines