Three Phase AC Question

Not enough info to be certain, but off the top of my head, the capacitance required will vary with the load applied.As load changes, the phases will become more unbalanced.

Google rotary phase converters for more info.

Also, a schematic of your idea would be helpful for more feedback.

How about getting a single phase motor and connecting it to a 3 phase motor so that when the single phase motor is powered up it spins the 3 phase motor generating 3 phase electricity!

Sorry, that is not a simple done thing.....

You can generate 3 phase from a 3 phase motor, but you need a lot of know how and engineering skills as well....

he should look here:-

http://en.wikipedia.org/wiki/Variable-frequency_drive

Most industrial locations in the U.S. are 3-phase.

If you have only 1-phase at your location, there are adjustable frequency drives that can produce 3-phase output from 1-phase input. Grainger has them up to 3 hp, 208-240 vac.

You can find frequency drives on eBay for a lot less $$. There are even ones made that have 120 volt single-phase input and 240 3-phase output over a frequency range from .1 hz to 600 hz.

Have a look at this one on ebay to get an idea of what's available.

http://cgi.ebay.com/Motortronics-ME2-2P5M-1-2HP-AC-Variable-Frequency-Drive-/250565739169?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item3a56e1c2a1

rotary phase converter

Dear Stepen

Actually Stephen, all North American and most if not all utilities world wide already produce electrical energy in three phase form at the source of generation be it through hydro electric, thermo nuclear, gas turbine, coal fired or geo thermo plants. This power generated is sent from these plants by transmision tower to various locations in three phase form or in some cases rectified to high voltage DC for transmission. The later is becoming more and more popular to reduce loses.

It is only at the local utilities that generally take this three phase energy and distribute in single phase form for residential and some small business use.

Regards James Archer

Hello Stephen,

From your letter I understood that you need a capacitor equipped phase converter in order to supply a three phase motor through a single phase supply. As a sophisticated project it can be a microprocessor controlled CYCLOCONVERTER. Apparently you don't want to spend that much funds. You rather prefer some simple capacitor system to achieve this phase conversion. I do have some info for 50Hz/220-380V system. This method may be feasible for small 3 phase motors. The info I want to pass you contains two simple drawings (I can describe the drawings rather than trying to pass images) and a chart for voltage-power versus cap values.

If motor windings are Y connected, you have to isolate one of phase windings and to connect a capacitor "C" in series, so you will have two branches to connect to one phase supply. One branch has two phase windings in series, and other branch has one "C" and one phase winding in series. Those two branches have to get connected parallel to supply (two wires).

If motor windings are DELTA connected, you have to open the connection between two phase windings, and to insert a "C" capacitor there. Now you have two terminals untouched and one terminal which you opened and a "C" capacitor inserted. Supply wires are going to be connected to those UNTUCHED terminals.

Now, you need THE CHART. I will give the chart as text in same sequence. The first COLUMN is power(Hp), the second COLUMN is "C" value for 220 volts, the third COLUMN is "C" value for 380 volts. Capacitor values as microfarads.

First column--- 0.1 Hp- 0.25 Hp- 0.50 Hp- 0.75 Hp- 1 Hp

Second column- 7.5-----12------27------42 ------60 uF (for 220V/50Hz)

Third column ---2.5 ------4------8.5 -----14------18 uF (for 380V/50 Hz)

You will need some calculations and experimenting regarding frequency and voltage changes. For the capacitors you can try to round to those values in the market, or connect in parallel to achieve the right value.