Single phase motor working theory

Single Phase Induction motor:-

》The single phase induction motor operation can be described by two methods double revolving field theory and cross field theory 113 is perhaps the easier of the two explanation to understand so we will discuss the double revolving theory only

Double revolving field theory:-

》》A single phase AC current supplies the man winding that produce a pulsating magnetic field 》》Mathematically Rakul setting friend would be divided into two field which are rotating in opposite direction
》》 the interaction between the field and current induced in the road Charbagh generates opposing torque

Starting torque:-

》》Single phase motor starting torque is zero  of the pulsating  single phase magnetic flux
》》 the starting of the motor requires the generation of a rotating magnetic flux similar to the rotating flux in three phase motor
》》 two perpendicular coil That Give current 90° out of phase can generate the necessary rotating magnetic field which start the motor
》》There are single phase Motors are built with  two perpendicular winding

》 the best gift is achieved by connecting
• A  resistance
• An inductance or
• A capacitor in series with the starting winding.

》 Most frequently used is a capacitor to generate the starting torque

》 Single phase induction motor are classified and name according to the method employed to make them self starting

(I).  split phase induction motor:- started by phase motor section through the use of auxiliary for starting winding
(II). Capacitor Motors:- standard 5 phase motor connection through the use of an auxilliary  and capacitor these are 

classified as:-
(a). Capacitor start induction run motor
(b). Capacitor run induction motor
(c). capacitor start capacitor run induction motor
(III). Shaded pole induction motor:- started by the motion of the magnetic field produced by means of shading coil around

☆ split phase induction motor☆

In this motor having two winding main winding and auxiliary winding ,hence these winding are 90° electrically each other and same 90° phase angle in these  winding. there are main winding having low resistance and high reactance and auxiliary winding have high resistance and low reactance .switch motor when attain 75% of its rated speed.
  》Working:-

Is lags by V because low reactance and high resistance and Im lag V by very large due to high reactance hence its starting torque proportional to sign thita . it disconnect after attain 75% speed from rated .

Centrifugal switch operation:-
                                                        It is connected in series with the head salary winding and mounted on the rotor shaft when the motor started and reaches 75% of synchronous speed centrifugal switch is mechanically  opened and in running condition auxiliary  winding remains  cut out from the circuit
Therefore motor run only with main winding

Characteristics:-

a.) Starting torque 1.5 times to 2 times the full load torque
b.) Starting current 6 to 8 time the full load current
c.) Low operating power factor 0.55 to .65
d.) Low efficiency 60 to 65%
e.) Power rating 1/20 to 1/2 kW
f.) Speed range 2875rpm to 700 rpm

Applications :-
                            It has low starting current and moderate starting torque. It is used for easily started load and typical applications  including fan, saw, washing machine, blower, centrifugal
pumps. etc.

Capacitor induction motor:-
1.) Capacitor start motor
2.) Capacitor run motor
3.) Capacitor start capacitor run motor

Capacitor start motor :-

                                           In this motor electrolytic capacitor used for starting the motor .in this  motor 90° phase angle for starting purpose the motor . Im' and Is' Im lags V' due to high reactance of main winding in there Is'lead V' due to capacitor  Im'and Is' angle is 90° . this motor having high starting torque .it is used in Lathes , drilling , fan, etc.

Cheracteristcs :-
a.) Starting torque 3.5 to 4.5 times the full load torque
b.) ∝30° to 80° from starting torque can be improved
c.) power factor very from 0.65 to 0 .75.
d.)Power rating 1/10 to 3/4 kW

Requirement of capacitor
》 Electrolytic capacitor are used as  starting capacitor value around 50 microfarad to a few hundred micro farad
》 Capacitor designed for extremely short time duty service and is guaranteed for not more then 29 period of operation / hr each period not axceed 3 seconds

Applications :-
This motor has high starting torque and therefore is used for hard start load such as pumps compressor refrigerator units machine tools etc.

Capacitor start capacitor run 

characteristics 

a ) starting torque 3 to 3.5 time the full load
b.) 60% efficiency opprox.
c.) Power factor .09
d.) Power rating 1/8 to 3/4 HP
e.) Pull out torque up to 260% of rated torque

Applications :-
》It combines the advantage of capacitor start and permanent capacitors and used for hard to start loads such compressor ,pump conveyors etc.
》 These motors are often employed requiring a quite operating motor such as in hospitals and  studios

Shadded pole motor theory of operations :-

 Small motor requiring only small starting torque may be made self starting by using low resistance copper bands called shadding bands. The emf induced in the shadding band cause a current to flow in the band . This current oppose the change of flux to which it is due and thus there is a time lag between the fluxes in the shadded and unshadded portion of the pole . The flux in the shadded portion of tge pole lags the flux in the rottor portion . the result is like a rotating field moving in the direction from the unshadded to the shadded portion of the pole and a starting torque is produced

characteristics :-
a.) Low starting torque 0.4 to 0.8 times the full load torque
b.) Efficiency 35% approximate
c.) Power factor 0.45 approx.
d.) Pull out torque 15% of full load torque
e.) Power rating 1/300 to 20HP ( 2.5 W to 40W)

Applications :- Because their poor starting torque low power factor and poor efficiency such motor are only suitable for low power applications such as for toys, portable fan, electric clock, hair drier, humidifier , photocopy machine etc.