Induction motor windings, number of turns per phase and per pole

  • #1
rulmismo
7
0
Hi,
I have some question regarding windings on induction motors, if anybody can help.
Reviewing some literature (*), the usual formulae to get the number of turns per phase of a induction motor winding is
  • Eph= RMS phase voltage [V]
  • Nph= number of turns of phase winding
  • f= frequency [Hz]
  • FL="involved" flux (typically set by a limit of Bmean * involved area, being Bmean about 0.7T for a typical machine) [Wb]
  • p=number of pole pairs
  • K= winding factor
Nph= Eph / (4.44 * f * FL * K )

My question is regarding the flux to be used. Most of the books and references I found talk in this equation of a "per pole" flux, but voltage in the formulae is phase voltage (and you can have several poles per phase winding), so my current understanding is:
- if p=1 (2 pole machine), Nph shall be concentrated in one winding, and flux involved is the "mean" of the whole machine
- if p=2,(4 pole machine), flux loading (Bmean) must be the same so I think:
if poles are feed in paralel (is this the usual case?), Npole=Nphase of the p=1 machine, to keep same flux loading.
if poles are feed in series, Npole=Nphase/p, to keep same flux loading (so same total turns, but distributed between the poles.)
- p=3....

I would appreciate any insight or correction, any reference to a worked example of higher pole machine design or windings could also help.

Thanks!

(*) References just in case can help anybody
ref1
ref2
ref3
 
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  • #2
Does the 4 pole motor uses single phase power? I am not sure why you would have a 4 pole motor if you have 3 phase power. If it is a single phase motor, the pole windings will have to have different reactance in order to create a phase difference between the two pole pairs. So the windings will depend on how that phase difference is achieved.

AM
 
  • #3
These are m-phase motor, in the usual case m is three, then phase windings are the same, but displaced 120º. My question is related to how many turns you would use per pole, so to keep flux within saturation limits.

A n-pole motor (with n>2) is used when you want a lower synchronous speed.
 

What determines the number of turns per phase in an induction motor?

The number of turns per phase in an induction motor is determined primarily by the voltage and current requirements of the motor, as well as the design of the magnetic core. Higher voltage applications typically require more turns per phase to adequately induce the required magnetic fields without exceeding the current density that the wire insulation can handle.

How does the number of poles affect the winding configuration in an induction motor?

The number of poles in an induction motor affects the winding configuration because it determines the frequency of the magnetic field changes needed to achieve the desired motor speed. More poles mean a lower speed at the same frequency of the power supply. This requires adjustments in the winding configuration to maintain efficiency and performance, often leading to different numbers of turns or different arrangements of the windings.

Can the number of turns per phase be adjusted after manufacturing?

Generally, the number of turns per phase in an induction motor is not adjustable after manufacturing as it is tightly integrated and sealed within the motor's construction. Altering the number of turns would require rewinding the motor, which is a complex and cost-intensive process usually not feasible outside of a professional repair or refurbishment setting.

What impact does changing the number of turns per phase have on motor performance?

Changing the number of turns per phase in an induction motor affects its impedance, which in turn influences the current draw and torque generation. Increasing the number of turns typically increases the motor's inductance and reduces its current draw, which can lead to higher efficiency but might reduce torque output. Conversely, reducing the number of turns can increase current draw and torque but decrease efficiency and potentially lead to overheating if not properly managed.

How is the optimal number of turns per phase calculated for a specific application?

The optimal number of turns per phase for a specific application is calculated based on the desired output characteristics of the motor, such as torque and speed, as well as the supply voltage and frequency. Engineers use electromagnetic theory and motor design principles, often assisted by computer simulations, to balance these factors and determine the most effective winding configuration that meets performance, efficiency, and durability targets.

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