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POWER FACTOR AND POWER TRIANGLE

  INTRODUCTION: The electrical energy is exclusively generated, transmitted and distributed in the form of alternating current.Therefore the question of power factor immediately comes into picture.Mot of the loads are inductive in nature and have Low Lagging power factor. Low power factor is highly undesirable as it causes an increase in current. POWER FACTOR: The cosine of angle between voltage and current in an AC circuit is known as power factor.  In AC circuits there is a phase difference  ɸ  between the voltage and current. The term  Cosɸ  is called the the power factor of the circuit. circuit is inductive, the current lags behind the voltage and the power factor is referred as lagging power factor. However in capacitive circuits, the current leads the voltage and is called as the leading power factor.                                                                                       (Figure 1.1) Consider an inductive load taking a lagging current I from the source. We can reso
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STARTING INDUCTION MOTOR USING RHEOSTAT.

  INTRODUCTION: Among several methods of induction motor starting, one and the oldest method is using Rheostat. It is a very old method and still in use  all over the world. A Rheostat is used to rise or lower the resistance of the circuit, to decrease or increase the current flowing through the circuit. We have two types of rheostats Wire wound rheostat and Liquid Rheostat . The logic behind the rheostat starting method is that we connect our rheostat in series with the rotor of the induction motor to reduce the initial torque of the motor i.e. limit the current flowing in the rotor. We will discuss both the rheostats one by one now. Wire Wound Rheostat:  It is just like a variable resistor and used to limit the current flowing through the circuit by changing its own resistance without any interruption.  (Figure 1.1) Figure 1.1 shows a wire wound rheostat used to start small slip ring induction motors. We can see that similar to potentiometers, rheostat is also a three terminal dev
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START DELTA STARTER FOR INDUCTION MOTORS

INTRODUCTION: As we discussed earlier that an induction motor needs some methodology for its starting. In this article we are going to discuss the second method of starting of an Induction motor known as START-DELTA STARER. Let us discuss that why and how this method supports to start an Induction motor.  Basic logic in Star-Delta method is that first we have to start the motor in Star connection and when the motor gains full speed at Star i.e. the change is speed becomes zero, then we have to switch the connection to Delta, then motor attains its rated r.p.m and can bear its full load. As we know that in Star connection Voltage is  under root three times less than the voltage in Delta. So as the power of the motor is constant and and voltage is less in star connection, the motor will draw less amount of current when started in star.We have to switch the connection from start to delta when the motor starts running smoothly and motor will behave normal and will bear full load. In older
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DIRECT ONLINE (DOL) MOTOR STARTING CIRCUIT

 INTRODUCTION: Induction motor is now a basic electric machine which is widely used domestically and obviously in industries all over the world. If we talk about the induction motor, we must know that all the induction motors need some methodology for their starting. For single phase motors we use capacitors for their starting to produce a phase difference between Voltage and Current. If we talk about the three phase motors, their are several methods to start them like DOL, STAR-DELTA, RHEOSTAT,SOFT STARTERS and the latest one is by using VFD . So, here we are going to discuss the simplest method of starting an Induction motor (single or three phase).  COMPONENTS: Fuses Breakers Contactor Over Load Relays Now we will discuss each component and its power rating according to the load.  Let us design a DOL circuit for a three phase 2HP motor working at 400V, so we have to calculate the ampere rating of fuses, circuit breakers and contactor. First of all we have to convert the motor ratin
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CAPACITORS

INTRODUCTION: Capacitor is a basic component of electronic circuits and basically it is used to store electrical energy for small periods of time. Capacitor is a passive component which store charge on its plates when connected to a source, and Capacitor stores the energy in the form of electric field.   The charged capacitor produces a potential difference (static voltage) across its plates just like a small rechargeable battery. CONSTRUCTION: Capacitors are of different sizes and power ratings but the basic construction of all of the capacitors it simple same. Capacitor consists of two parallel metallic plates placed close to each other but not physically/electrically connected but are separated by Dielectric. Dielectric  is some medium like air, paper, mica, ceramic or some liquid gel used in electrolytic capacitors. Because of this dielectric, capacitor blocks the DC as it doesn't gives any conducting path for the current to flow. So it could be a logical reasoning of the fact
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