Can Capacitors Create Specific Phase Shifts in DIY Three-Phase AC Systems?

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    Ac Phase Three phase
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Discussion Overview

The discussion revolves around the creation of a three-phase AC system using capacitors and single-phase AC lines, specifically in the context of DIY projects involving a rotating magnetic field. Participants explore the feasibility of achieving specific phase shifts and the necessary parameters for constructing a stator.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant, Stephen, inquires about using capacitors to achieve a 120-degree phase shift for the second leg and a 240-degree phase shift for the third leg in a three-phase system derived from single-phase AC lines.
  • Another participant asserts that it is not possible to create three-phase power using three individual single-phase AC lines and capacitors.
  • A different participant mentions the historical use of 'shaded pole' motors to convert single-phase supply into two phases and suggests that a combination of resistors, inductors, and capacitors can produce any desired phase shift, albeit with potential power dissipation issues.
  • Stephen also asks whether using two AC lines with one having a capacitor in series would create a rotating magnetic field and seeks clarification on the proper method for layering coil turns in the construction of the stator.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of using capacitors to create specific phase shifts in a three-phase system. There is no consensus on the methods proposed, and the discussion remains unresolved regarding the best approach to achieve the desired outcomes.

Contextual Notes

Participants have not fully explored the implications of power ratings, coil configurations, or the specific electrical characteristics required for achieving the desired magnetic field strength. The discussion includes assumptions about the effectiveness of various methods without detailed mathematical analysis.

Who May Find This Useful

This discussion may be of interest to hobbyists and engineers involved in DIY electrical projects, particularly those focused on AC systems, magnetic fields, and motor design.

StephenD420
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Hello everyone

I am trying to make a small three phase ac stator so a rotating magnetic field will be produced. I can use a ring with an outer diameter of 3 inches and an inner diameter of 1.5 inches with each of the six poles being 1 inch with about 100 turns of 24 magnet wire or a ring with an outer diameter of 8 inches and an inner diameter of 6 inches with each of the six poles being 2 inches with about 200 turns of 24 magnet wire. Since I live in the US we only have single phase ac, not three phase. I bought a variable frequency drive that produces three phase ac from single phase ac but it is only 4 amps and since I would like to make my magnetic field about .5 to 1 Tesla I do not know if that will be enough? Is it enough? Will this be enough turns to get the .5 to 1 Tesla?

The most important question I have regarding the three phase power is that I know you can use 3 individual single phase ac lines and use a capacitor to make two of the three legs 90 degrees apart. Is there a way to use capacitors to make the second leg 120 degrees out of phase from the first leg and the third leg 240 degrees out of phase from the first leg?

Thank you so much for your help.
Stephen
 
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oh the small ring is about 1/8 inch in depth with 1/8 inch depth coil forms(iron or steel) and the larger ring is about 1/8 inch in depth with 1/2 inch depth coil forms(iron or steel)

Thanks
Stephen
 
StephenD420 said:
The most important question I have regarding the three phase power is that I know you can use 3 individual single phase ac lines and use a capacitor to make two of the three legs 90 degrees apart. Is there a way to use capacitors to make the second leg 120 degrees out of phase from the first leg and the third leg 240 degrees out of phase from the first leg?

Thank you so much for your help.
Stephen

No, you cannot make 3 phase power using 3 individual single phase ac lines and capacitors.
 
It was common to use a 'shaded pole' in order to get an induction motor to work by turning a single phase supply into two phases. All old tape recorders and record players used this cheap arrangement.

Using the right combination of R, L and C and a transformer (to get a phase reversal), you can produce any phase shift you want but it can involve dissipating a lot of power in your resistor (likewise, a shaded pole motor runs hot, although it only delivers very low mechanical power).
 
How about just using two ac lines with one haivng a capacitor in series? Would that create a rotating magnetic field or would it be pulsing, as I want it to rotate counterclockwise in space around the inside of the stator ring?

Also, how do you layer coil turns for a coil? Do you just start at the top of the coil form and then coil over the top of the previous coil in the same direction and then just twist the two endings together for the leads at the top and bottom of the coil?

Thanks.
Stephen
 

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