ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
AreMetal Ladders Ever OK For Electrical Work?
by HotLine1. 01/22/18 07:31 PM
Photocell
by twh. 01/22/18 05:06 PM
VDE 0100 to introduce AFCIs
by sparky. 01/20/18 05:09 PM
MRI LED lights dimmer control replacement - wow!
by Potseal. 01/19/18 08:52 PM
New in the Gallery:
Housebilding DIY wiring
SE cable question
Who's Online Now
0 registered members (), 31 guests, and 12 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 1 of 2 1 2
Phase Inverter/converter question #15253
10/11/02 06:58 PM
10/11/02 06:58 PM
A
arseegee  Offline OP
Member
Joined: Jan 2002
Posts: 324
Statesboro, GA USA
A customer of mine has a custom wood working shop at his house. I wired the shop two years ago and it has a 200A 1ph service.

He is purchasing a new moulding machine and vac system that that requires 3ph. The motors will draw a total of 142A @ 240V/3ph.

Having 3ph power from the poco is inot an option. He is miles from any three phase primaries

I have never converted 1ph to 3ph and was wondering how this conversion effects amperage on the primary. Will the draw be greater on the primary or will the secondary equal the primary.

Any one with any formulas for me?

Work Gear for Electricians and the Trades
Re: Phase Inverter/converter question #15254
10/11/02 07:25 PM
10/11/02 07:25 PM
C
caselec  Offline
Member
Joined: Apr 2002
Posts: 558
San Jose, CA
It looks like your going to be doing a service change. If the motors draw that much there is no way your 200 amp service is going to be able to supply enough power for the required size rotary phase converter. I'm guessing you will need at least 300 - 350 amps single phase just for this equipment. Do a search on Google for "rotary phase converters" and you should be able to find some sizing info.

Curt


Curt Swartz
Re: Phase Inverter/converter question #15255
10/11/02 07:50 PM
10/11/02 07:50 PM
S
scjohn  Offline
Member
Joined: Jul 2002
Posts: 74
charleston, SC, USA
Just as caselec suggested, converting single phase to three phase with a converter doesnt relieve the primary at all. The load is pretty much the same.
John

[This message has been edited by scjohn (edited 10-11-2002).]

Re: Phase Inverter/converter question #15256
10/11/02 09:19 PM
10/11/02 09:19 PM
Scott35  Offline

Broom Pusher and
Member
Joined: Oct 2000
Posts: 2,708
Anaheim, CA. USA
To add some information here, the complete picture - Power Suplying System and Load Device - will have a fixed KVA level. The load draws "X" amount of KVA and the supply must be able to deliver at least the same "X" KVA level, or the load will not be able to draw the required True Power (Wattage) it needs to develope the required Horsepower and Torque.
Results are a decrease in Rotor speed when the work exceeds the maximum HP which the Motor can develope.
This causes most Induction Motors to stall when they slip too far behind or come within a Syncronous Frequency point.

So much for the boring babble! [Linked Image]

I ran some numbers and here are the results:

<OL TYPE=1>

[*]Using the listed 142 Amp @ 240 VAC 3 Phase figure, this equals 58.96 KVA - 58,958.4 VA to be exact,

[*]58.96 KVA on the Single Phase side relates to 245.83 Amps @ 240 VAC 1 Phase.
</OL>

Just something to consider.

P.S. here's the formulas used:

KVA:

I x E / 1000 [1 ph.] I x E x 1.73 / 1000 [3 ph.]

Amperes:

KVA x 1000 / E [1 ph.] KVA x 1000 / 1.73 x E

Scott S.E.T.


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
Re: Phase Inverter/converter question #15257
10/11/02 09:39 PM
10/11/02 09:39 PM
A
arseegee  Offline OP
Member
Joined: Jan 2002
Posts: 324
Statesboro, GA USA
Scott35, Thanks. I went to my ugly book to work it out but couldn't figure out how to convert back on the line side of the converter...???? (I think I confused myself there!)

I'll have to get more info from the manufacturer on this machine. The only specs I have got is the 100 amp requirement on the moulder and a 15hp vac system.

Re: Phase Inverter/converter question #15258
10/11/02 09:46 PM
10/11/02 09:46 PM
C
caselec  Offline
Member
Joined: Apr 2002
Posts: 558
San Jose, CA
Scott35 - I agree with your math but a phase coverter is not 100% efficient.

Arseegee - try this link http://www.phaseconverter.com/rotary-converter.sizing/


Curt Swartz
Re: Phase Inverter/converter question #15259
10/11/02 10:14 PM
10/11/02 10:14 PM
A
arseegee  Offline OP
Member
Joined: Jan 2002
Posts: 324
Statesboro, GA USA
Caselec, that's what I was thinking. Thanks for the link too!

To add a note, this machine has 4 motors on it. A 2hp, 7.5hp, 10hp & 15hp. All drive different spindles. Then the dust system has another 15hp motor on it.

Guess it's gonna be a service upgrade. But who could have dreamed of a $35K planer/moulder at someones house.

Re: Phase Inverter/converter question #15260
10/12/02 12:26 AM
10/12/02 12:26 AM
B
Bjarney  Offline
Moderator
Joined: Apr 2002
Posts: 2,527
West-Southern Inner-Northeast ...
Online application info at sites like: http://www.gwm4-3phase.com/appguide.htm

Also, don't forget NEC Article 455.

Re: Phase Inverter/converter question #15261
10/12/02 06:50 AM
10/12/02 06:50 AM
S
scjohn  Offline
Member
Joined: Jul 2002
Posts: 74
charleston, SC, USA
Dohh.. didnt do the math. The load isnt "pretty much the same".
Sorry for the hasty inacurate post.
John

Re: Phase Inverter/converter question #15262
10/12/02 08:40 PM
10/12/02 08:40 PM
T
Trainwire  Offline
Member
Joined: Mar 2002
Posts: 360
Strasburg,PA,USA
Um, that is going to be one whacking great converter. something to suggest would (wood? [Linked Image]) be to replace or spec the motors to be single phase. Then you are looking at "just a service upgrade" rather than also adding a converter. Your probably into rotary converters to get any kind of efficency out of it, great amount of floor space, and noise too. the noise of the converter probably isn't an issue because a 3 spindle moulder can be heard several counties over anyway.

Just a thought.

Trainwire

Page 1 of 2 1 2

Featured:

2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
NickD
NickD
Amish Country, PA
Posts: 46
Joined: March 2013
Show All Member Profiles 
Top Posters(30 Days)
Admin 21
sparky 15
Potseal 15
Popular Topics(Views)
243,601 Are you busy
180,416 Re: Forum
170,871 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.028s Queries: 15 (0.006s) Memory: 1.0245 MB (Peak: 1.1998 MB) Zlib enabled. Server Time: 2018-01-23 19:58:14 UTC