Plugging is the simplest type of braking which involves re-connection of motor to supply in such a way that motor develops torque in opposite direction to the movement of rotor system, speed will decrease till zero speed is reached where mechanical brakes are applied and then it will accelerate in opposite direction. This method is […]
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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.
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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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The armature control method works on the principle that the speed of the DC motor could be varied by varying the back emf. Fig. 1: Armature Control Method of DC Motor.
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A smooth variation of speed from zero to above normal with inherent stability of speed at all loads is achieved through an adjustable voltage system of speed control called Ward-Leonard Method of speed control. Fig. 1: Ward Leonard Method of Speed Control.
What is Ward Leonard Method of Speed Control? Working Principle, Diagram & Applications Read More »