phase converter

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  #1  
Old 11-03-10, 07:16 PM
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phase converter

I want to run a 25 HP 3 phase motor on a band saw mill. I have a 400 amp 220 single phase service. I have been told I need a 50 HP rotary converter. I have a temco 30 HP converter now. Can I add another converter to this 30 hp converter I have and if so what kind of soft switch is needed to start these converters? Thanks Steve
 
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  #2  
Old 11-04-10, 09:07 AM
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Have you tried just the 30HP TEMCo alone? I don't think you'd really need to oversize all the way to a 50HP since a band mill should be fairly easy on the motor to start compared to something like a pump or compressor.

What kind of duty cycle do you plan for the mill? Length of time running, type of milling?

I would probably size the single-phase side of the circuit for 125A (#1 copper conductors in conduit, #6 copper ground).

** Actually which model TEMCo do you have? The AC21 or AC29?
 
  #3  
Old 11-04-10, 04:18 PM
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I might just give it a try and see what happens. The Temco I have is an older model where the control box and motor are seperate. It is a 21 KW . Thanks Steve
 
  #4  
Old 11-05-10, 08:07 AM
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Okay for the 21kW unit you probably want to go a little lower on the circuit ampacity -- something like 100A (#3 copper in conduit). Although a 125A breaker would still be within the range of what you could if there's a problem starting the motor.

Don't forget to check your phasing with the belt off when you first start the motor.
 
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Old 11-05-10, 10:54 AM
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Before you do anymore with that exsting phase converter do you have any other three phase motours in that unit beside the large 25 HP motour ??


Normally the band saw can start unloaded but how long to ramp up to the speed depending on how it set up and It may be wise idea to have VSD or soft start on there to limit the inrush current during start up especaily you have phase converter in there.

Merci.
Marc
 
  #6  
Old 11-05-10, 05:46 PM
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I have some 3 phase shop equipment I will use when not using saw mill, but nothing I use at the same time as mill. Thanks Steve
 
  #7  
Old 11-05-10, 09:40 PM
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Ok just a quick question what voltage you are running on three phase side 240 volts or 480 volts ??


The reason why due I can able come up with few quick answer to see how much current drawage on your phase converter.

Merci.
Marc
 
  #8  
Old 11-06-10, 08:29 PM
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240 volt 3 phase. Also how close to the converter should the mill be? Thanks Steve
 
  #9  
Old 11-07-10, 12:07 AM
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Originally Posted by cubdriver55 View Post
240 volt 3 phase. Also how close to the converter should the mill be? Thanks Steve
Really there is no specfic distance unless stated by manufacter requirement and the conductor { wire } sizing so let me give you a quick run down how this work and keep in your mind I will be using THHN/THWN copper conductors in the conduit unless stated otherwise.

Ok here a quick example under 50 feet you can use 25mm˛ { # 4 AWG } three conductors and 16mm˛ { # 6 AWG } for grounding conductor.{ see below about warning on connections }

The conduit size it will be minum of 1 inch but I rather keep it at 1 1/4 inch or larger.

This part above is on three phase side so on below part I will deal with single phase this part will get ya if not carefull.

I will use 30 KW @ 240 volt Single phase which it will draw 125 amps for this conductor size you will need 50mm˛ { #1 AWG } two hot conductors but you will need minum conduit size of 1.5 inches.

Now let me give you a head up and good warning with any rotary or static phase converters the single phase side is not a issue as long you use proper colour marking however this part will get you majorty of the phase converters will useally wired on Delta format and there will be one phase to ground will have oddball voltage so you will see it in a second.

Phase A and Phase C are straight connection so that is not a issue but phase B { Some models will use phase C as wild leg connection } will have wild leg connection so it mean from the line B or C depending on model to ground or netural will result voltage of 208 or 190 depending on set up and with wild leg connection you have to use the orange tape or marker { this is very important detail } the reason why you have to mark it due if you have any equiment that have any 120 volt devices in there so you can avoid this part without blow something up with wild leg which I have see it pretty often if not carefull.


And finally I did keep the voltage drop to minuim level { typealy 3.5% or less } and single phase side that will cover it up to about 50 to 60 feet after that you have to bump up the conductor size up.

If need more question just holler here one of us will help ya.

Merci,
Marc
 
  #10  
Old 11-07-10, 05:45 AM
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OK sounds great #1copper on single phase side hot legs #6 ground but what size for neutral? Thanks Steve
 
  #11  
Old 11-07-10, 04:09 PM
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Originally Posted by cubdriver55 View Post
OK sounds great #1copper on single phase side hot legs #6 ground but what size for neutral? Thanks Steve

Steve.,

Belive or not.,

None is needed if the equiment do not have any netural connection at all and majorty of equiment I dealt they useally have control transfomer installed in there { 240 - 24 volt tranfomer set up } but few case they will have 240 - 120 volt transfomer in there as well.

Merci.,
Marc
 
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