Many of the loads installed in present-day power systems are harmonic current generators. Combined with the impedance of the electrical system, the loads also produce harmonic voltages. The nonlinear loads may therefore be viewed as both harmonic current generators and harmonic voltage generators. Prior to the 1970s, speed control of AC motors was primarily achieved using belts and pulleys. Now, [...]
In this article we will discuss about the meaning and laws of resistance to electric current. Meaning of Resistance: Resistance may be defined as that property of a substance which opposes (or restricts) the flow of an electric current (or electrons) through it. The practical as well as mks (or SI) unit of resistance is ohm (Ω), which is defined [...]
Gustov Robert Kirchhoff derived two basic laws governing the distribution of electric currents in a network, one commonly known as first law or current law (KCL) or point law, whereas the second is called second law or voltage law (KVL) or mesh law. Law # 1. Kirchhoff's First Law or Current Law (KCL) or Point Law: According to this law [...]
In this article we will discuss about: 1. Meaning of Alternating Current 2. Generation of Alternating Emf 3. Sinusoidal Quantities (Emf, Voltage or Current) 4. Average and Effective (RMS) Values of Alternating Voltage and Current 5. Average and Effective (RMS) Values of Sinusoidal Current and Voltage 6. Form Factor and Peak Factor of Sinusoidal Wave and Other Details. Contents: Meaning [...]
In the most of the ac circuits, it is necessary to consider the combined action of several emfs or voltages acting in a series circuit and several currents flowing through the different branches of a parallel circuit. Let it be required to add two currents given by the equations: i1 = I1 max sin ωt and i2 = I2 max [...]
In this article we will discuss about: 1. Introduction to Alternating Quantities 2. Phasor Diagram Using RMS Values 3. Conventions. Introduction to Alternating Quantities: Assumed that alternating voltages and currents follow sine law and generators are designed to give emfs having sine waveform. The above said assumption makes the calculations simple. The method of representing alternating quantities by waveform or [...]
In this article we will discuss how to determine effective value of alternating current and EMF, explained with the help of a suitable graph. In a graph plot the instantaneous values of current along the ordinate and the corresponding angular displacements along the abscissa for one complete cycle or 360°. A Sine curve will be obtained as shown in figure [...]
The following devices take leading current from the supply line: 1. Static Capacitor or Condenser 2. Over-Excited Synchronous Motor 3. Phase Advancer. Device # 1. Static Capacitor or Condenser: Static capacitor takes a current which leads the applied voltage by about 90°. Thus, it acts in direct opposition to inductance, neutralizes the inductive influence of the circuit and improves the [...]
The below mentioned article provides a suitable formula for calculating capacitance of the capacitor. Two metal plates separated by an insulator constitute a capacitor or condenser, namely an arrangement which has the capacity of storing electricity as an excess of electrons on one plate and a deficiency on the other. The insulator between the plates is called dielectric. It may [...]
The below mentioned article provides a formula for calculating power factor in the A.C. circuit. The power in watt absorbed by a d.c. circuit is known when the supply pressure in volt across the circuit is multiplied by the current in ampere flowing through the circuit. But in an a.c. circuit the product of supply pressure and the circuit current [...]