DC Machines

This guide covers DC Servo Motor and Stepper Motor Working Principle, Block Diagrams, and their Applications. Further, it also covers Brushless DC Motor Operating Principle and its Applications. DC Servo Motor Working A DC servo motor is usually defined as any motor that can be remotely controlled by providing negative …

This guide covers armature reaction in DC Machine (Generator and Motor) and how to correct it using Brush Shift, Compensating Winding, and Interpoles. An armature, when rotating in its magnetic field, can have varying values of current flowing in its coils. The current can vary from zero at no load …

This guide covers efficiency and losses of DC Machines (Motor and Generator) which include Copper, Core, Brush, Mechanical (Friction and Windage), and Stray losses. Losses in DC machines (motor and generator) include friction, windage and electrical losses. Friction is present in all rotating machinery. Windage is present because of air …

The voltage induced in a single coil of a DC generator is alternating. A commutator is therefore necessary to ensure that the current in the external circuit always flows in the one direction. During the brief interval when a coil is short-circuited by a brush, the current in the coil …

This article mainly covers DC Motor Construction and its Parts with labelled diagrams. Furthermore, a cutaway view of the DC Motor is presented and discussed in detail.    The main parts of a typical DC motor are: field frame or yoke end-shields and bearings field poles field coils armature and …

When a conductor is moved through a magnetic field, a voltage is induced across the conductor by electromagnetic induction. Electromagnetic induction is the fundamental principle underlying electrical generators. A DC generator is one of the simplest generators to understand, so it is introduced first. Classification of DC Generators Several types …

This article covers various types of starters for the DC motors including: Manual Starters Automatic Starters Definite Time Starters Counter EMF Starter Current-Limit Starter Each type of starter along with its circuit diagram is described in detail in this section. Manual Starters Recalling the equivalent circuit of a DC motor, …

The major advantage of DC motors has been the ability to control the speed-torque characteristic over a fairly wide range of speeds for a given torque. Variable-speed AC drives now make it possible to use induction motors to perform tasks that previously could only be done by DC motors. However, …

DC Motor Speed Characteristics When a load torque is applied to a motor, the motor will slow down due to the load opposing the machine’s rotation. Eventually, the machine’s electromagnetic torque will equal the load torque and a new steady-state speed will be reached. How the speed changes depends on …

The losses in a DC machine affect its cost, rating, and performance. The efficiency of a rotating machine is frequently determined by measuring the losses, using techniques that are precisely defined by ANSI, IEEE, and NEMA measurement standards. The efficiency is defined the same way as it is for transformers …

The magnetization curve produced when the machine is separately excited still applies in the case of self-excited DC generator. That is, a given value of field current will produce a specific value of the generated voltage at a given speed, regardless of how the field winding is connected. However, there …

As shown by equation 1, the terminal voltage of the separately excited DC generator would be expected to decrease in a linear manner due to the voltage drop across the armature circuit resistance. $\begin{matrix}   {{V}_{t}}={{E}_{a}}-{{I}_{a}}{{R}_{a}} & {} & \left( 1 \right)  \\\end{matrix}$ Figure 1 shows the linear decrease that would …

When operated as a generator, the armature of the DC machine is driven by a prime mover. As the armature coils move through the flux created by the stator field, a voltage is induced in them. To understand the operation of the DC generator we need a specific relationship for …

The voltage source inverter is a somewhat older design and less expensive to implement. Various implementations of the VSI are also known as six-step, twelve-step, or even eighteen-step inverters. Voltage Source Inverters Operation  In the VSI, the switches are turned on and off at regular intervals to deliver rectangular pulses …

The induction motor is basically a constant-speed motor, as it operates within 3% of the synchronous speed, which is determined by the frequency and number of poles in the machine: \[\begin{matrix}   {{n}_{s}}=\frac{120\times f}{P} & {} & \left( 1 \right)  \\\end{matrix}\] Although torque at a given slip is proportional to the …