Basic Logic Gates and Boolean expressions

The goal of this module is to enable learners to apply basic logic gates and Boolean expressions to digital circuits. Objectives A learner will be able to: Explain the difference between analog and digital quantities Give examples of binary numbers and describe their structure Give examples of hexadecimal and octal …

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Number Systems in Digital Electronics

The goal of this module is to provide learners with skills and practice necessary to enable them to convert between number systems used in digital electronics. Objective The learner will be able to Explain the difference between analog and digital quantities Give examples of binary numbers describe their structure Give …

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Buck-Boost Transformer Working Principle

An isolation transformer can be wired as an autotransformer in a buck configuration

A buck-boost transformer is a type of transformer which is primarily used to adjust the voltage level applied to various electric equipment. Buck-boost transformers are utilized in in several applications such as uninterruptible power supplies (UPS) units for computers. When an existing AC electrical circuit suffers from excessive voltage drop …

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Starting Methods of Three Phase Induction Motor

Results of Y-Delta motor start

Three-phase Induction motors draw six or more times rated current when started at rated voltage. Such high currents may pose serious problems for the motor and the electrical system when large motors are started. One way to reduce the starting current is to start the motor at reduced voltage. After …

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Three Phase Induction Motor Performance

Characteristic curves of an induction motor

Using the equivalent circuit of the three-phase induction motor and some additional information about the mechanical and core loses, one could calculate the performance of the three-phase induction motor from no-load to full-load. Figure 1 shows a set of generic curves of efficiency, current, power factor, and slip for an …

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Torque Speed Characteristics of Induction Motor

Induction motor torque-speed characteristic 2

Figure 1 showed a plot of induction motor torque vs speed from zero to synchronous speed. This curve is called the torque-speed characteristic curve. We can derive an equation from the equivalent circuit that allows the calculation of the torque for a given value of slip. FIGURE 1    Induction motor …

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Three-Phase Induction Motor Efficiency

Power flow diagram for an induction motor

The equivalent circuit of the induction motor can be used to examine the losses and the efficiency of the machine. Efficiency is defined for an induction motor the same way as it is for any device: \[\begin{matrix}   \eta =\frac{Power\text{ }Out}{Power\text{ }In}=\frac{{{P}_{out}}}{{{P}_{in}}} & {} & \left( 1 \right)  \\\end{matrix}\] Defining the …

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Three Phase Induction Motor Equivalent Circuit

Per-phase induction motor equivalent circuit

The three-phase induction motor operates in some ways like a transformer. In the transformer, AC voltage is applied to the primary, which creates AC flux in the core. That flux links the secondary and induces a voltage of the same frequency, but with a voltage that depends on the transformer …

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Three Phase Induction Motor Working Principle

difference between dc motor and dc generator

The three-phase induction motor, like all electric motors, operates by means of interaction between magnetic fields. The stator magnetic field in a three-phase induction motor rotates around the air gap between the stator and the rotor. The direction of field rotation determines which way the motor turns and is controlled …

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Three Phase Induction Motor Construction

Exploded view of a three-phase induction motor

Like all motors, a three-phase induction motor contains a stator (the stationary part) and a rotor (which rotates). Each contains electrical windings that carry current and thus creates a magnetic field. The interaction of the magnetic fields creates the torque that rotates the rotor and the load. Figure 1 shows …

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Electronic Voltmeter Working and Block Diagram

Electronic Voltmeter

An analog electronic voltmeter uses an electronic amplifier to improve the performance of an electromechanical voltmeter. For example, an electronic voltmeter has a much higher input resistance than an electromechanical instrument, so voltmeter loading effect is considerably reduced. Also, voltage levels that are normally too small for measuring on an …

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Conductors and Insulators Definition and Examples

cable cross section

Conductors carry electric current. Insulators protect conductors and protect people from conductors. Whether a material is a conductor or an insulator depends on its atoms and on the relationship of each atom to its surrounding atoms. Insulators may break down if subjected to excessive voltages. Similarly, conductors may be destroyed …

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Three Phase Transformer Construction

2500 kVA power transformer.

A transformer consists of two or more electrical windings that are linked together by a magnetic field. Except for special-purpose transformers, the coupling is enhanced with a ferromagnetic core. Transformers are often drawn as shown in Figure 1, with the primary coil on one leg and the secondary coil on …

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