Permanent magnet motors are similar to conventional DC motors except the use of permanent magnet to produce flux instead of field winding. The use of high energy permanent magnet in the motors which advances in the field for the purpose of simplicity and low initial cost has led to the formation of new class of […]
What is Permanent Magnet DC Motor (PMDC Motor)? Construction, Diagram & Applications Read More »
Swinburne’s test is the simplest indirect method to determine the efficiency of D.C machine. In this test the no- load losses are measured separately and from their knowledge, efficiency at any desired load can be predetermined in advance. Figure 1: Arrangement of Swinburne’s test.
What is Swinburne’s Test of DC Motor? Theory & Diagram Read More »
Retardation Test is used for finding the efficiency of shunt wound DC machines. In this test, the rotational losses or stray losses are measured and from their knowledge efficiency at any desired load can be determined. Figure 1: Arrangement of Retardation Test.
What is Retardation Test (or Running Down Test) of DC Motor? Theory & Circuit Diagram Read More »
Figure 1: Arrangement of Brake Test. Brake test is a direct testing method used to find the efficiency of a DC motor. The arrangement for performing brake test on a DC motor is shown in figure (1).
What is Brake Test of DC Machine? Theory, Circuit Diagram & Advantages Read More »
The different methods of speed control of DC shunt motor are, Armature control method Field control method Ward-Leonard method. Armature Control Method
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A four point starter is a protective device used in shunt and compound DC motors to limit the high starting current in the absence of back e.m.f. The construction of four point starter is similar to three point starter except the connection of NVC (No-volt coil).
What is a 4 Point Starter? Working Principle, Construction & Diagram Read More »
Speed-Torque Characteristics of DC Shunt Motor The speed-torque characteristics of DC shunt motor are also known as mechanical characteristics. They can be obtained from torque-current and speed-current characteristics of DC shunt motor.
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Torque Production in DC Motor Consider a DC motor with stator and rotor. When the stator coils are energized, a stator magnetic flux is set up and follows the path as shown in figure (a) with no current in the rotor conductor.
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Figure 1: Interpoles. Interpoles are small poles placed in between the main poles of a D.C generator as shown in figure (1). Interpoles are also known as commutating poles or com poles. In generators, the polarity of the inter pole is same as the main pole which is ahead of it in the direction of
What are Interpoles in DC Machines? Theory, Connection Diagram & Uses Read More »