static converter

[a.bisnath]

presently ,at short notice trying to build a 220 volt single phase to 220volt 3phase supply by making a static converter, I have arranged the contactors for start and run transition, the motor is 1 horse power,is there any way to try to determine the capacitor values for start and run beside trial and error?

 

[norcal]

Why not use a VFD? They are cheap & no need cobble anything together....


Edit: 1 HP drives are avail. w/ 120V or 240V 1? input.

 

[jminer99er]

Contact Jreaf on here he knows rpc. If I remember correctly its about 80-100 MF per hp.

There is also a forum dedicated to vfd, rpc, and xfmrs at practical machinist. You could probably use the search function there and you will get plenty of info from theads about building static and rpc.

I do know with a static converters, you only get 2/3 your horsepower rating.

 

[kwired]

Contact Jreaf on here he knows rpc. If I remember correctly its about 80-100 MF per hp.

There is also a forum dedicated to vfd, rpc, and xfmrs at practical machinist. You could probably use the search function there and you will get plenty of info from theads about building static and rpc.

I do know with a static converters, you only get 2/3 your horsepower rating.

2/3 of what horsepower rating? Are you saying that for a 2000 watt output you need to input 3000 watts? Or are you talking about amperage on the input line vs what the amperage for a true three phase supply would read? You have to remember 1 hp is 1.73 times more current for single phase than three phase at the same voltage but volt amps is the same.

I'm sure there is some ineffeciency. A VFD especially on that small of a motor is easy to use and is efficient.

 

[stew]

the 2/3 hp rating is due to the fact that you do not actually have a true 3 phase waveform to work with. The motor regardless of what you do with a static converter will only give you 2/3 of the rated hp of any motor (if that). some are even lower than 2/3.

 

[a.bisnath]

static converter

o.k. I agree a vfd may be the simplest answer or a electronic phase converter which will convert 1 phase to 3 phase
but the customer a small machine shop owner cannot afford one at the moment,and I am trying to see what can be done with simpler,cheaper and more readily available components that can be quickly interchanged if there is a problem,I guess l also I came from a time where it was important to understand how the components worked,the underlying principles and build it from scratch equations and all .I do admit I am a little rusty now

 

[LarryFine]

... the customer a small machine shop owner cannot afford one at the moment,and I am trying to see what can be done with simpler,cheaper and more readily available components that can be quickly interchanged if there is a problem ...

Keep the cost of burned-out motors in mind when comparing costs. Just in case you do some learning on his nickel..

 

[norcal]

o.k. I agree a vfd may be the simplest answer or a electronic phase converter which will convert 1 phase to 3 phase
but the customer a small machine shop owner cannot afford one at the moment,and I am trying to see what can be done with simpler,cheaper and more readily available components that can be quickly interchanged .........

If one wants to play, one has to pay. A 1 HP drive can be had pretty cheap, labor costs will eat up your saving rather just buy & install a drive then program it.

For those who use a VFD for phase conversion, Teco drives seem to be well regarded.

 

[jminer99er]

The nice thing about a RPC is that you can run multiple motors, unlike a static or vfd. I made one from a 10hp idler and it runs two mills and a lathe and some 3ph grinders.

 

[jminer99er]

I made this for my dad and gave it to him at Christmas, with a big red bow

My dad being without his mills for five years said "I was going to sell these because I didnt know how to get them running, nor did I have the money to." "This is the best xmas gift I have ever got!... Having my mills working again is better then sex!" lol

He used a small static converter, and when he would run his BP, the motor would "chatter/knock" (his description) and he thought it was bearings.

 

[hurk27]

The problem with static converters is imbalance, this can kill a motor very fast from over heating, and the % of imbalance will ex-potentially reduce the available HP you can safely use the motor at, unless using it for very short duration periods, such as for saws, drilling and such, you must lower the load you put on the motor, or the motor will get too hot, I second the use of VFD's as having the best balanced output along with being the most efficient, second would be RPC, but only for short duration loads do I ever use a static.

Constant loads that have the motor already sized for the load such as fans, Blowers, and pumps, will always get a VFD.

Here is a good site that does give allot of info on converters, as long as you keep in mind they are in the business of selling converters, but its still good reading that will bring some understanding to what you want to do.

Don't forget to click on the other links at the top of the page for more subjects about converters:

http://www.phaseconverterinfo.com/phaseconverter_voltagebalance.htm

 

[Rick Christopherson]

There is lots of misinformation about static converters, even for this normally well informed website. Anyone that tells you that the greatest detraction to a static converter is the "2/3 power loss" doesn't understand what a static converter really is.

A store-bought static converter is nothing more than a motor starter! Once the motor is up to speed, the converter disconnects, and the motor is left to run from single-phase power. We all know how bad that is.

Installing balancing capacitors will change this, and store-bought converters can be upgraded to make them balanced converters. Any static converter that has a multi-HP range is not balanced. (However, RPC's will be effective over a range.)

As was mentioned, for the low cost of small VFDs, static converters are not a good choice, even if you upgrade them to a Balanced Static Converter.

 

[kwired]

I made this for my dad and gave it to him at Christmas, with a big red bow

My dad being without his mills for five years said "I was going to sell these because I didnt know how to get them running, nor did I have the money to." "This is the best xmas gift I have ever got!... Having my mills working again is better then sex!" lol

He used a small static converter, and when he would run his BP, the motor would "chatter/knock" (his description) and he thought it was bearings.

How much did the size 3 starter cost in comparison to a VFD? Plus all the other stuff if it were new. Looks like a stainless enclosure also.

 

[Open Neutral]

Looks like a stainless enclosure also.

That set off my $$$ detector ASAP.

 

[stew]

Take a look at the arco rotophase units. I have used these for many years for mutimotor operation and have had superior success with them. never a motor failure and no overheating.A very fine multimotor unit IMHO

 

[a.bisnath]

open delta transformer

open delta transformer

do appreciate the ideas and opinuions, may I ask you thoughts on a small tansformer in open delta connection which will also give a 3 phase supply from the 220 volt single phase

 

[LarryFine]

... may I ask you thoughts on a small tansformer in open delta connection which will also give a 3 phase supply from the 220 volt single phase

Read this: http://forums.mikeholt.com/showthread.php/134550-Transformer-Question