phase converter

Status
Not open for further replies.
R

rickl

Senior Member
hi i'm a new ec i have a client that just bought a 3 phase converter that he needs installed, he has 4 3 phase 230 volt pieces of equipment that draws 16,15,8,4 amps and the converter is rated at 9 hp, i told him that i think its to small but he was told by the salesman that this converter would handle the load.does this sound right? i've never worked with converters before.
what i would like to do is use the converter to feed a 3 phase panel then feed all 3 phase
equipment from there.one of my concerns using the manufacture wire diagram is they show L1 & L2 being tapped off feeding the phase converter through a fused disconnect and my 3 phase panel then t3 coming off the converter to the my panel to get the 3 phase my concern is what happen when the disconnect is turn off and someone start the equipment on single phase. there has to be a better design than what the manufacture idea is.
has anybody designed something like this before any help would be greatly appreciated
 
Re: phase converter

Here is an excellent site to gather information.
http://www.phaseconverter.com/
I am not reconmending the product just the site. I have used this site for the same questions you are asking. Good luck. But you have to also find out if the customer is going to be running all the equipment at on time or just on piece of equipment at a time.I feel that the converter should be at least 15 HP if he/she is going to be running everything at the same time. If not you base the size of the converter on the largest piece of equipment with a little room.
 
Re: phase converter

thanks
he says he'll only be running one piece of equipment at a time, but you know how that goes he'll be calling in a couple of months complaining that the converter burned up
 
Re: phase converter

I agree. 9HP sounds like plenty for any single (or certain combinations of) load, but underated for your 4 loads simultaneously. (per highkv's linked site).

here's a few comments beyond that...

1. this is a rotary converter, right? Static converters (if even available that large?) don't generate true 3PH, so you could get some squirrely performance starting/running mixed &/or multiple loads.

2. single-phasing a 3PH load can create non-starts, underspeed, low power out, overheating (and probably some other things depending on the device). Some of these things may be critical depending on the application.

3. about your wiring plan: I'm not sure I understand completely. If you tap L1 & L2 after a 2-line disconnect but before the converter, you won't have a 1PH to worry about when the disconn is open. A 3-line disconn and a 2-line disconn would work also, as long as you don't tap L1 & L2 before the 2-line disconn. (if I'm picturing this correctly)
 
Re: phase converter

yeah its a rotary,
the drawings i seen show L1 & L2 are tapped before the phase disconnect. basicly L1 & L2 goes from the single phase panel to the 3phase panel you install a j box to tap off L1 & L2 to feed the converter thru a disconnect, then you bring T3 from your converter to your 3 phase panel. so what i'm saying is if the phase disconnect is open L1 & L2 are still proving 240 volt single phase to the 3 phase panel.
 
Re: phase converter

something I didn't mention is that the converter is typically switched on/off when needed. that is to say you aren't setting up an always-live 3ph circuit. so, before starting your end device(s), you start the converter. likewise, after shutting down your load(s), you shut down the converter.

so, this would explain the diagram you have. (i.e. it's assumed user knows to start converter and then start load (or) stop load then stop converter, in those orders.)

to fool-proof for your 1PH concerns, the switching logic needs to eliminate the converter off/load on state.
 
Re: phase converter

It sounds to me like you have a rotary that is similar to the Arco Roto-Phase model M. That unit is designed for a total connected load of 9 hp with no single motor over 3 hp and inddeed you can run all the load at once. I freccomend starting the largest motor first and then bringimng on the smaller ones. You however have a load that is too large for the model M. You neeed a model A which is designe4d for a total connected load with no single motor over 5 hp. You seem to have 2ea5 hp motors a 3hp and a 1 hp as using the nameplate amps you have given.This la0od will run nicely on the model A as long as you start the 2 5 hp first and then add the rest of the load. The load is just slightly(1hp) over the rating of a model A but I have found over the years taht the Arco brand has more fudge factor than other brands. The one thing to re4member is that if this is a machine shop application or similar the loads will actually be variable in nature and will priobably never reach the full load amps of the motors. I used to won an electric motor business for 17 years and sold hundresd of thes units over the years. Would never sell the static type but had excellent results with the Arco and never had a call back with problems that could not be easily cured. Be absolutly certain that you size tyour wire size exactly as the instructions show. Remember you are intially dealing with single phase amps so your input wire is sized accordingly up yo your disconnect. Dont skimp on wire size as this is the most common error on install. If I can help further please contact me if you wish. Joe
 
Re: phase converter

Sorry I missed a line there. Ther model is good for no single motor over 5 with a total connected load of 15 hp. Any combination of laod as long as no single motor is over 5 hp.
 
Re: phase converter

thanks
stew i might be looking you up if i get the bid. the code say you size your single phase conductor and overload 2.5 times your 3 phase full load current. the size of the converter i agree with you, but he already bought & the saleman said it will handle the load. will see
 
Re: phase converter

rick this model has the exacgt same capacity as the arco model m. 3 hp largest motor and a total connected load of not to exceed 9 hp. Found Kay industries on line with a sizing chart etc. looks to mer like you need thier model ma-1 which is the same as arcos model r. 5 hp max with a total connected load of not to exceed 15. His is too small to handle the largest motor .

[ November 30, 2004, 11:41 PM: Message edited by: stew ]
 
Status
Not open for further replies.
Top