Wednesday, 23 October 2013

MATLAB program to compute the back EMF and armature current of a DC Motor


clc; clear all; P = input('Number of poles are: '); Phi = input('Flux per pole in Wb is: '); Z = input('Total number of armature conductors are: '); N = input('Armature speed in rpm is: '); V = input('Supply voltage in volts is: '); Ra = input('Armature resistance in Ohms is: '); W = input('1 for lap wining and 2 for wave winding: '); if W == 1 Eb = (Phi * N * Z) / 60; end if W == 2 Eb = (P * Phi * N * Z)/120; end Ia = (V - Eb)/ Ra; disp('Back EMF developed in the motor in volts is:'), Eb disp('Armature current in A is: '); Ia

Sunday, 20 October 2013

Response of RL and RC circuits plot


% To plot response of RL and RC circuits % R = 10, L = 20e-3 H for RL circuit V = 100; % Volts R = 10; % Ohms L = 20e-3; % Henry Im = V/R; to = L/R; t = 0:10e-6:0.02; i = Im*(1-exp(-t/to)); figure(1) plot(t,i) title('Response of R-L circuit') xlabel('T (sec)'), ylabel('i(t)') % R = 100, C = 20e-6 F for RC circuit R = 100; C = 200e-4; Vm = V; to = 1/(R*C) t = 0:10e-6:6; v = Vm*(1-exp(-t/to)); figure(2) plot(t,v) title('Response of R-C circuit') xlabel('T (sec)'), ylabel('v(t)')

Series and parallel resonance response


% This program plot a graph of frequency vs impedance in case of series % resonance clc; clear all; f = 100:1:400; L = 6.34e-3; C = 100e-6; R = 100; XL = 2*pi*f*L; XC = 1./(2*pi*f*C); Z = (R^2 + (XL - XC).^2).^0.5; figure(1) plot(f,Z) title('\bf Impedance vs frequency plot for series resonance'); xlabel('\bf Supply frequency in Hz'); ylabel('\bf Impedance in Ohms'); Z = 1./(1./XL+1./XC); figure(2) plot(f,Z) title('\bf Impedance vs frequency plot for parallel resonance'); xlabel('\bf Supply frequency in Hz'); ylabel('\bf Impedance in Ohms');

Wednesday, 2 October 2013

Design of Seven step multi level inverter


The concept of utilizing multiple small voltage levels to perform power conversion was patented by an MIT researcher over twenty years ago. Advantages of this multilevel approach include good power quality, good electromagnetic compatibility (EMC), low switching losses, and high voltage capability. The main disadvantages of this technique are that a larger number of switching semiconductors are required for lower-voltage systems and the small voltage steps must be supplied on the dc side either by a capacitor bank or isolated voltage sources. The first topology introduced was the series H-bridge design. This was followed by the diode clamped converter which utilized a bank of series capacitors. A later invention detailed the flying capacitor design in which the capacitors were floating rather than series-connected. Another multilevel design involves parallel connection of inverter phases through inter-phase reactors
. In this design, the semiconductors block the entire dc voltage, but share the load current. Several combinational designs have also emergedsome involving cascading the fundamental topologies. These designs can create higher power quality for a given number of semiconductor devices than the fundamental topologies alone due to a multiplying effect of the number of levels.

Monday, 2 September 2013

Design of DC power supply by diode capacitor bridge


This diode capacitor bridge is widely used for power supplies intended to function over extreme input voltage ranges. In this circuit there are only three valid configurations. When the voltage is first applied diode D1 quickly becomes ON. Assume that the initial capacitor voltages are zero. Since the capacitor voltage is initially zero diode D1 and C2 conducts and supply current to the load. Also the current flows through C1 as when D1 is ON Vin is identical to Vc1. Since the RC time constant is very slow compared to the sinusoidal changes in input supply C2 will not charge up much. As long as D1 is ON Vc1 must track Vin. This configuration will remain valid shortly after Vin has peaked.  Simulation of this configuration is carried out in MATLAB and the output load voltage and capacitors current as observed are shown in the figure. 

Rectified output for half and full wave by Matlab code