phase converter size

[sthojlft]

Just joined...
Not sure if this is correct place to post...

Have acquired a auto lift for garage that is all electric and have a few questions-

The lift is powered by a 2.2 KW 3 phase 3 hp 220v motor. I will be needing a rotary phase converter but I am getting conflicting information on the size of converter needed.

The set-up will be connected to my home 220v 30amp dryer circuit. What I have been told so far is that all I need is a 3 hp converter but others (TEMCO, Phoenix) tell me that this is in no way big enough and that I need a 10 hp converter... It was stated the this set-up is a "hard" start thus the need for a bigger converter motor.

The phase converter will be lift dedicated...it will not power anything else.

THX

 

[mrb]

can you just replace the lift's motor with a single phase one?

 

[sthojlft]

anything is possible

i'm just trying to go least cost least intrusive...

from this site it appears rpc can be home built pretty cheaply...

anyway...I'm no electrical genus but this is for a Stenhoj all elec. auto lift and it seems all the up down switching is going to be 3 phase....but again this is not my area of expertise...

 

[A_Pmech]

The rating of a phase converter will vary depending on the manufacturer. It's like small engines were a few years ago, before the big lawsuit. The same engine might be rated "6 HP" by one manufacturer and "4 HP" by another. The important thing is to go by their ratings. If they say you need a bigger unit, you need a bigger unit.

Phase converters are easy to build and need not be anything more complicated than a 3-phase motor and a fusible disconnect. For a clean phase-balanced design suitable for running machine tools, look up the "Fitch Williams" plans on Practical Machinist.com A properly built converter based on a 7.5HP motor would be MORE than sufficient for your application.

 

[sthojlft]

thanks for response.....

however still in the dark

Simple question-

I HAVE A 220v 3 PHASE MOTOR ON AN ALL ELECTRIC AUTO LIFT. TO PUT THIS IN MY GARAGE WITH 120 HOUSE CURRENT HOW BIG OF A ROTARY CONVERTER DO I NEED. THIS WILL BE A DEDICATED CIRCUIT....NO OTHER MOTORS.

THE CONVERTER SELLERS SEEM TO THINK I NEED 10HP.....

thx

 

[A_Pmech]

thanks for response.....

however still in the dark

Simple question-

I HAVE A 220v 3 PHASE MOTOR ON AN ALL ELECTRIC AUTO LIFT. TO PUT THIS IN MY GARAGE WITH 120 HOUSE CURRENT HOW BIG OF A ROTARY CONVERTER DO I NEED. THIS WILL BE A DEDICATED CIRCUIT....NO OTHER MOTORS.

You'll need to begin by running a 220V single-phase circuit.

THE CONVERTER SELLERS SEEM TO THINK I NEED 10HP.....

thx

That will depend on the converter manufacturer and how they rate their converters. Some manufacturers who rate their converters on the largest single motor their converter will start may say a 3HP converter will be sufficient. Other manufacturers who rate their converters on the maximum total small motor load capacity (always higher than the maximum single motor capacity) may say you need a 10HP converter.

There are no standard sizing rules that can be applied between manufacturers.

 

[930dreamer]

I use the X2 the Tool hp, in sizing rpc for hard start machinery. I say a 7.5hp rpc should be fine. Not an expert though. Build a larger rpc and get a 3 phase compressor.

 

[nehog]

...

THE CONVERTER SELLERS SEEM TO THINK I NEED 10HP.....

thx

And there is some reason you think they don't know what they are talking about? They are (one would hope) experts on their own products, and if they say 10 HP for this application then I'd suspect there is a reason for that recommendation.

A lift must start at full load (consider: car is up a certain height, and you want it up more: you hit raise and it (should) go up.) But that requires more starting power than a smaller converter would be able to provide...

I think (IMHO, whatever!) the main issue is that problem of full-load starts with a lift. Saying "well I'd just never do that" is not meaningful to them as they will think "Some day he, or someone else, will do just that..."

Personally, I like the idea of converting it to single phase (new motor) and perhaps you could post a picture of the motor so those who know them could suggest how to replace it.

 

[sthojlft]

yes...I have a 220v circuit in my garage...sorry I left this out.

My confusion...
1) The rpc sellers recommend a 10 hp motor- [my issue is the person on the other end of the phone is not an expert but a sales person who is referencing a generic chart that I too could reference and they are CYA for the worst case. In addition, this person has never built one in their garage...]

2) There are references to having too big of rpc for ones application...in these forums +

3) A local shop will build me one and the person was adamant that all I need for a 3hp motor is a 3 hp rpc and this person also stated (#2) that one can have too big of a rpc...

go figure...appreciate the help.....

 

[sthojlft]

++
To replace the 3 phase motor with a 1 phase motor would I not need a bigger hp single phase motor since the 3 phase motor is most efficient..???

 

[A_Pmech]

It's not possible to have "too big" of an RPC. Larger than necessary, yes, but not "too big". A converter that is larger than necessary will have a higher than full load generated leg voltage and will use a bit more electricity at idle due to the larger frame size.

FWIW, switching out the motor is certainly another option, but you'll have to replace the size 0 starter with a size 1 starter. The control circuit should not require any modifications beyond reconnecting the control transformer.

Hopefully, your pump uses a common C-mount motor with a keyed shaft rather than a tang-drive. Tang drive motors are application specific and tend to be hard to locate.

 

[rsanter]

look at the rating on the converter
a converter that is a 3hp one will power a 1-3hp motor from that
a converter that is a 10 hp will power up to a 10hp motor but is better used on more like a range of 5-10hp motors
short answer is dont get the 10 unless you plan on adding other 3ph equipment

another note
I dont think you need a rotary converter
a static converter or better yet a VFD I think is the better option
look on ebay, I would think you could get a VFD for your application for $200 to $300 and be set

bob

 

[sthojlft]

[rsanter]

can u be a little more specific...

Your saying---
-If I get a rpc all I need is a 3hp for my 3hp "hard start" motor?

-I thought static inverters, after start, dropped to an output of 1/3 less?... so what size static inverter do I need?

-could u give me a little more info on a VFD?

THX

 

[rsanter]

[rsanter]

can u be a little more specific...

Your saying---
-If I get a rpc all I need is a 3hp for my 3hp "hard start" motor?

-I thought static inverters, after start, dropped to an output of 1/3 less?... so what size static inverter do I need?

-could u give me a little more info on a VFD?

THX

static and rotary are not the same thing
a static converter is a set of capacitors (sized properly) and a few other things that will power 2 legs of the motor and kind of shunt power to the 3rd leg. once the motor is running the magnetic field will hely to 'self gen' the third leg. the big deal is to get a 3ph motor going on only 2 legs (so to speak)

this is the reasoning behind the 'you loose up to 1/3 of the motors rated HP'
and yes it is true you will not get full power out of a motor using a static converter

a rotary ph converter is a 3ph motor that has a static converter stuck to the side of it. the RPC motor is the one that will be adsorbing the losses so the motor you are using will have 'full rated HP'
so to make a RPC they take a say 6hp motor and stick the right capacitors and stuff on it and then tell you 'this is a 4hp RPC' which means that you can start up a 4hp 3ph motor using it. for a hard start motor contact the company that made it and ask them as I am sure they have specs on what you will need but I am not confident that you need a 10hp unit

if your unit has a 3hp 3ph motor on it I could have bought into then telling you that you need a 5hp or even 7.5hp unit but the 10 to me sounds a little like what he has on his shelf or that he dosent know what he is talking about so he is over selling you because it only your money.
hey what do I know, Im just giving an opinion from my gut that I think you need to talk to someone that knows more and do a little more research before plunking down the money

bob

 

[Charles (in GA)]

While a lift does start with a load (in the air and want to go higher), it isn't that much more. This must be a huge lift, designed for heavy vehicles. My Challenger 9K lb lift has a 2 hp motor on it (single phase) and it doesn't grunt or groan (though I haven't had anything heavy on it, a Ranger PU isn't heavy, but I agree with rsanter that I too could have bought into them telling you a 5 hp or a 7.5, but using a 10 hp to run a 3 hp motor is kinda outlandish. Yes, you can, and if you ever get any three phase machinery (or a compressor I suppose, though it seems kinda crazy to keep a RPC idling just to run a compressor when it cycles on and off) you might appreciate the extra size.

Me, I'd go with a 5 hp and call it good. You will have more than enough power.

What kind of lift is it?

Does the power pack look anything like this? This is the Exact same power pack that is on my 9,000 lb Challenger two post lift. $450 plus shipping.

http://www.surpluscenter.com/item.asp?item=9-7139&catname=hydraulic

Charles

 

[sthojlft]

to be clear my lift is ALL electric...there are NO hydraulics...thus [IMO] the bigger motor.

Its a 20 year old Stenhoj Maestro lift. Its a "low profile" with the max post height of 8.5 feet.

http://www.stenhoj.dk/Autolift/forside/menu/lift.htm

Its the one on the lower right of this link but my older one has a chain and chain housing across the bottom.

 

[sthojlft]

here is the motor

 

[nehog]

Humm, that's exactly what I pictured... Not sure why others were thinking hydraulic!

I think you'd be cheaper with a VFD (go to eBay and search, ton of them there) but if you wanted a single phase motor would probably fit there as well. But a new motor would be much more than the VFD...

 

[rsanter]

quality motors are expensive
a RPC is a motor with a static converter attached

I would compair price between the replacement motor 220v single
and the RPC
converting that over to a single ph motor will be eatier than one with the hydrolics

bob

 

[sthojlft]

nehog-

so is a VFD the same as a digital solid state phase converter?

What is the down side to a VFD?

What size do I need ...a 3hp is ~ $338 on ebay.

Do I need to purchase an additional 3 phase motor for the VFD?

THX

 

[rsanter]

A VFD will take AC electricity in (single or 3 ph) and then turn it to DC.
it will then turn it back to AC digitally/electonically

the purpose is that it will allow you to vary the frequency in order to change RPM of the motor

for you use you will just be using it to convert single ph to 3ph but will also allow you to slow the rate of life if you wanted. not sure why you would want but you could

disadvantage
the VFD will 'soft start' in that it will start at a low RPM and wind up slowly whick is better for control or motor life in most instances.
you can go in and reprogram a faster ramp up speed.
also, when you turn it off it will ramp down the RPM slowly (but you can change that too) so it wont be like a flip the switch and instant stop where you want.
you can get use to that and will learn to estimate when to hit the switch when you are close to where you want

a 3hp VFD will be for 3ph in and out. there will be another rating for using single ph in and 3ph out.
look the specs up online or call the manufacturer.
generally you will need to get a 4-5hp rated VFD

benifits
the VFD will give you very close to clean and true 3ph power so you will get 96-98% of the rated HP of that motor its on

bob

 

[Cap-n-Cray]

I am converting a 3 phase mill to run on single phase 220V. I got a Teco FM50 VFD for a 3 HP motor from FactoryMation for less than $200. Might check them out.

Cary

 

[Falcon67]

Get the VFD. As for the "soft start" - well, that is programmable and you can ramp it up quick. You can also control spin down, e-stop and other motor operations. A VFD is a good thing. I bought a mill with a 3 phase motor just because I could buy a VFD and convert the mill controls to run the VFD. Makes for a much nicer machine IMHO than a 220V single phase machine.

>so it wont be like a flip the switch and instant stop where you want.
I can stop my mill motor real quick. I can also instant reverse. Just program the appropriate input. I have a normal soft stop 2 second spin down and 3 second spin up with e-stop set to .2. When I hit e-stop, that motor stops. Now.

 

[Charles (in GA)]

Humm, that's exactly what I pictured... Not sure why others were thinking hydraulic! ...

Considering that direct electro-mechanical lifts are as rare as they come, why would you expect anything other than hydraulic? This is German made, so its not your ordinary garden variety lift. Virtually all lifts are hydraulic, have been for years.

Charles

 

[Norcal]

That motor is a metric frame motor, may be expensive to replace, a NEMA frame motor not likely to just bolt in, and a 3 HP & smaller VFD is low cost, above that the prices start shooting up.

 

[sthojlft]

If I were to build a RPC can anyone help me locate a 5 - 7.5 hp 3 ph surplus motor in Georgia?

Thanks

 

[landydoni]

I just bought the same lift for my shop (got a crazy deal on it too) and am in the same boat, what did you end up doing? Going with a new single phase motor or a phase converter? If you went with the converter which type did you go with and did you build or buy it? Thanks for the info.