Author: John Mulindi
-
Factors to consider when selecting a Motor for a particular application
When selecting a motor for a specific industrial application, there are several factors and specifications that you should consider. We look at these factors that will guide you when choosing the appropriate motor for your industrial use. The following are some of the key questions or factors that you should consider when choosing the suitable…
-
Performance Characteristics of Digital Measurement Instruments
In this article, we discuss the performance characteristics of digital instruments i.e. Resolution Accuracy Linear errors Settling time Temperature sensitivity Monotonicity Resolution This is defined as the smallest increment in voltage that can be discerned. It is the reciprocal of the number of discrete steps in the Digital to Analog (D/A) converter input. Resolution depends…
-
Pulse Width Modulation (PWM) Speed Control of a DC motor
We can control the speed of a motor using an open loop control or closed loop control strategy. The open loop control is the simplest form of motor control; here we simply set the drive voltage value and the motor characteristics and the load determines the operating speed & torque. But you will find that…
-
Root-mean-square (r.m.s.) value
We know that a current passing through a resistance has a heating effect, the magnitude of which we measure in watts, that is power is given by This shows that power (or heat) dissipated in a resistance is proportional to either square of the current or the voltage. Related: The Basics of Electric Circuits Consider…
-
The Basics of Semiconductor Physics as the Foundation of Electronics
Metals have a large number of weakly bound electrons in what is called their conduction band. When an electric field is applied to a metal such as copper, the electrons migrate freely producing a current through the metal. Because of the ease by which large currents can flow in metals, they are called conductors. In…
-
Basic Electronics – Multiple Choice Questions & Answers (MCQ1)
The Answers to these questions have been provided towards the end: Q1. A Transistor is a? A. Current controlled voltage device B. Current controlled current device C. Voltage controlled current device D. Voltage controlled voltage device Q2. The breakdown mechanism in a lightly doped p-n junction under reverse biased condition is called? A. Zener breakdown…
-
Speed Control of a DC Compound Motor
A compound motor is a combination of a series and a shunt-wound motor. The Speed-torque characteristics for a compound motor Speed Control of a DC Compound Motor Speed is controlled by variable resistors in the shunt field and armature circuit. The series winding may be arranged that it aids the shunt field (cumulative compound) or…
-
DC Shunt Motor Speed Control
In the shunt motor, the motor winding is in parallel with the armature. From the figure above, the supply current I = Ia + If . Unlike a series motor, if the load is removed from the motor, only the armature current will decrease, the field remaining at the same strength. Therefore the motor will…
-
Speed Control of a DC Series Motor
The dc series motor has its windings and armature connected in series across the supply. From the figure above, the armature current Ia also supplies the field, hence when Ia is large on starting for example, the magnetic field will be strong, and the torque will be high. As the machine accelerates, the torque, armature…
-
The Essential Components of An Electric Drive
Power electronics deals with the applications of solid-state electronics for the control and conversion of electric power. The conversion techniques require switching power semiconductor devices ON and OFF. The block diagram below shows the essential components of an electric drive controlled by a power semiconductor converter. The converter regulates the flow of power from the…