Author: workhouse123
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AC CIRCUIT CONTAINING PURE INDUCTANCE ONLY
The circuit containing a pure inductance of L Henry is shown in Figure 7.3. Fig. 7.3 Circuit containing pure inductance only Let the alternating voltage applied across the circuit be given by the equation; ν = Vm sin ω t (7.4) As a result, an AC i flows through the inductance that induces an emf in it, given by the relation; This induced emf is equal…
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AC CIRCUIT CONTAINING RESISTANCE ONLY
The circuit containing a pure resistance of R Ω is shown in Figure 7.1. Let the alternating voltage applied across the circuit be given by the equation; Fig. 7.1 Circuit containing resistance only ν = Vm sin ω t (7.1) Then, the instantaneous value of current flowing through the resistor will be; The value of current will be maximum when ω t = 90° or sin ω t = 1 Im = Vm/R…
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INTRODUCTION
Alternating supply is invariably used for domestic and industrial applications. The path for the flow of alternating current is called an AC circuit. In DC circuits, the opposition to the flow of current is only the resistance of the circuit. While in AC circuits, the opposition to the flow of current is due to resistance (R),…
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APPLICATIONS AND SELECTION OF DC MOTORS
As per the characteristics of DC motors, different types of DC motors are applied for different jobs as follows:
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CHARACTERISTICS OF COMPOUND MOTORS
There are two types of compound-wound DC motors, namely cumulative compound motors and differential compound motors. Cumulative compound motors are most common. The characteristics of these motors lie between the shunt and the series motors. The N − Ia characteristics, T − Ia characteristics, and N − T characteristics are shown in Figure 11.53(a), (b), and (c), respectively. Fig. 11.53 (a) N−Ia, (b) T−Ia and (c) N−T characteristics of shunt…
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CHARACTERISTICS OF SHUNT MOTORS
The conventional diagram of this motor is shown in Figure 11.45. In these motors, the shunt field current Ish = V/Rsh remains constant since the supply voltage V is constant. Hence, the flux in DC shunt motors is practically constant (although at heavy loads, somewhat flux decreases due to armature reaction). Fig. 11.45 Conventional diagram of a DC shunt motor 11.23 CHARACTERISTICS OF SERIES…
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CHARACTERISTICS OF DC MOTORS
The performance of a DC motor can be easily judged from its characteristic curves known as motor characteristics. The characteristics of a motor are those curves that show relation between the two quantities. On the basis of these quantities, the following characteristics can be obtained: The following important relations must be kept in mind while…
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COMPARISON OF GENERATOR AND MOTOR ACTION
It has been seen that the same machine can be used as a DC generator or as a DC motor. When it converts mechanical energy (or power) into electrical energy (or power), it is called a DC generator and when it is used for reversed operation, it is called a DC motor. Table 11.1 gives the comparison…
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Brake Horse Power
In the case of motors, the mechanical power (H.P.) available at the shaft is known as brake horse power (BHP). If Tsh is the shaft torque in Nm and N is speed in rpm, then useful output power = ωTsh = 2π NTsh/60 W
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SHAFT TORQUE
In DC motors, whole of the electromagnetic torque (Te) developed in the armature is not available at the shaft. A part of it is lost to overcome the iron and mechanical (friction and windage) losses. Therefore, shaft torque (Tsh) is somewhat less than the torque developed in the armature. Thus, in the case of DC…