INDUCTION MOTOR 2

1.)

in Simulink :

we can decide what is the rotor type in the motor.

we can put all the values of the equivalent circuit in parameters.

it consists of the following circuit:

In the equivalent circuit R₁ represents, the resistance of the stator winding and X₁ the stator leakage reactance (flux that does not link with the air gap and rotor). Magnetizing reactance required to cross the air gap is represented by X_m and core losses (hysteresis and eddy current) by R_c.

An ideal transformer of N1 and N2 turns respectively represents the air gap. For the rotor side, the induced emf is affected by the slip (as the rotor gains speed, slip reduces and less emf is induced). The rotor resistance and reactance are represented by R₂ and X₂; with X₂ being dependant on the frequency of the inductor rotor EMFs.

the final formula is:

and the nomenclature of other terms be :

2.)

3.)

%Calculating Voltage per phase 
V1 = 230/sqrt(3); 
% Number of phase 
Nph = 3; 
% Number of poles 
Poles = 4; 
%  Stator Resistance (R1)  &  Rotor Resistance (R2) 
R1 = 0.095%; 
R2  = 0.23%; 
 %  Stator Inductance (X1)  &  Rotor Inductance (X2) 
X1  = 0.680; 
X2  = 0.672; 
% Magnetising Inductance 
Xm  = 18.7; 
% Variable Frequency 
n1 =  [10:10:50]; 
for fz  = n1 
%  Calculating Ws wrt Frequency 
omegas=(4*pi*fz)/poles; 
ns =(120*fz)/poles; 
Zleq = j * Xm * (R1+j*(X1))/(R1+j*(X1+Xm)); 
Rleq = real(Zleq); 
Xleq = imag(Zleq); 
Vleq =abs(V1 * j * Xm  /  (R1+j*(X1+Xm)));  
for n=1:200 
      %  Calculating Torque – Speed 
S (n)=n/200; 
rpm(n)=ns*(1-S(n)); 
I2  = abs(Vleq/(Zleq+(1i*X2)+(R2/S(n)))); 
Tmech(n)  = nph*(I2^2)* R2 /(S(n)*omegas); 
end 


hold on 
% Plotting  Torque vs RPM 
plot(rpm,Tmech) 
title (\'Torque-Speed Characteristics of Induction Motor\') 
xlabel(\'rpm\') 
ylabel(\'Torque (N-m)\') 
legend(\'10Hz\' , \'20Hz\' , \'30Hz\' , \'40Hz\' , \'50Hz\') 
grid on  
end 

output results in :

4.)

BLDC:

Construction:

A BLDC doesn’t use brushes for commutation but rather they are electronically commutated. In conventional Brushed DC Motors, the brushes are used to transmit the power to the rotor as they turn in a fixed magnetic field.

Construction of BLDC Motor

The main design difference between a brushed and brushless motors is the replacement of a mechanical commutator with an electric switch circuit. A BLDC Motor is a type of synchronous motor in the sense that the magnetic field generated by the stator and the rotor revolve at the same frequency. Brushless Motors are available in three configurations: single-phase, two-phase and three phases. Out of these, the three-phase BLDC is the most common one

A BLDC motor consists of two main parts: a stator and a rotor.

Stator:

The structure of the stator of a BLDC motor is similar to that of an induction motor. It is made up of stacked steel laminations with axially cut slots for winding. The winding in BLDC is slightly different than that of the traditional induction motor.

Generally, most BLDC motors consist of three stator windings that are connected in star or ‘Y’ fashion (without a neutral point). Additionally, based on the coil interconnections, the stator windings are further divided into Trapezoidal and Sinusoidal Motors.

In a trapezoidal motor, both the drive current and the back EMF are in the shape of a trapezoid (sinusoidal shape in case of sinusoidal motors). Usually, 48 V (or less) rated motors are used in automotive and robotics (hybrid cars and robotic arms).

Rotor:

The rotor part of the BLDC Motor is made up of permanent magnets (usually, rare earth alloy magnets like Neodymium (Nd), Samarium Cobalt (SmCo) and alloy of Neodymium, Ferrite, and Boron (NdFeB)).

Based on the application, the number of poles can vary between two and eight with North (N) and South (S) poles placed alternately.

Position Sensors (Hall Sensors):

Since there are no brushes in a BLDC Motor, the commutation is controlled electronically. In order to rotate the motor, the windings of the stator must be energized in a sequence and the position of the rotor (i.e. the North and South poles of the rotor) must be known to precisely energize a particular set of stator windings. A Position Sensor, which is usually a Hall Sensor (that works on the principle of Hall Effect) is generally used to detect the position of the rotor and transform it into an electrical signal. Most BLDC Motors use three Hall Sensors that are embedded into the stator to sense the rotor’s position. The output of the Hall Sensor will be either HIGH or LOW depending on whether the North or South pole of the rotor passes near it. By combining the results from the three sensors, the exact sequence of energizing can be determined.

Working Principle

Consider the following setup of three windings in the stator designated A, B, and C. For the sake of understanding, let us replace the rotor with a single magnet.

When a current is applied through a coil, a magnetic field is generated and the orientation of the field lines i.e. the poles of the generated magnet will depend on the direction of the current flowing through the coil. Using this principle, if we supply current to the coil A so that it will generate a magnetic field and attract the rotor magnet. The position of the rotor magnet will shift slightly clockwise and will align with A. If we now pass current through coils B and C one after the other (in that order), the rotor magnet will rotate in a clockwise direction. To increase efficiency, we can wind the opposite coils using a single coil so that we get double attraction. Further increasing the efficiency, we can energize two coils at the same time so that one coil will attract the magnet and the other coil will repel it. During this time, the third will be idle.

For a complete 3600 rotation of the rotor magnet, six possible combinations of the coils A, B, and C are applicable and are shown in the following timing diagram.

At any time, one phase is positive, one phase is negative, and the third phase is idle (or floating). So, based on the inputs from the Hall Sensors, we have two switches the phases as per the above diagram.