Load Test or Back to Back Test or Sumpner’s Test of Transformer

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This article outlines the Load Test of Transformer. Load Test of Transformer is also known as Back to Back Test or Sumpner’s Test.  Load Test of a Transformer is basically carried out for determining the maximum temperature rise of the Transformer. However is not viable to conduct this test by connecting the secondary of the … Read more

Stray Load Loss and Mechanical Loss in an Electrical Machine

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Stray Load Loss: As we know that, when an electrical machine is loaded, load current flowing in the armature winding of the machine produces an mmf which distorts the space distribution of mmf produced or set up by the field winding in the air gap. This distortion of space distribution of mmf or flux density … Read more

How Space Harmonic in Rotating MMF wave Produces only Fundamental Frequency Voltage in Stator?

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It is a well known fact that, space harmonic present in the rotating mmf wave in an uniform air gap Electrical Machine (Non Salient Pole machine) produces or generates only fundamental frequency voltage in the Stator winding of the machine. In this post we will discuss the reason behind this fact. As we know that … Read more

Why Current through an Inductor lags Behind Voltage?

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For understanding the reason, why current through and Inductor lags behind Voltage across the Inductor, we will first go mathematically then we will understand the concept analytically. Let us consider a purely inductive circuit as shown in figure below. As shown in the figure above, an inductor of value L Henray is connected with an … Read more

Why DC Series Motor has High Starting Torque?

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DC Series Motors are widely used for the purposes requiring high starting torque like in Hoist, Crane, Electric Traction etc. In this post we will discuss the reason behind the high starting torque of DC Series Motor. For any DC motor, torque is directly proportional to the flux and armature current i.e. Ƭ = KaØIa  … Read more

Pick-up Current, Plug Setting Multiplier (PSM) and Time Setting Multiplier (TSM)

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Plug Setting Multiplier and Time Setting Multiplier are used only for Electromechanical Relays. These terms or parameters are not so used in Numerical Relays but they are conceptually used and incorporated in Numerical Relays too but the way of their implementation is quite different than that of Electromechanical Relays. In this post we will focus … Read more

Why Number of Stator and Rotor Poles must be Equal for Production of Electromagnetic Torque?

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This is very basic but important concept to understand Electrical Machine. It is well known fact that, the number of stator and rotor poles must be equal for the production of net Electromagnetic Torque. In this post we will discuss the reason behind this. Let us consider an Electrical machine having 2 Stator Poles and … Read more

Detrimental Effects of Armature Reaction

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As discussed in earlier post, Purpose of Interpole in DC Machine, there are two types of effect of armature mmf on the main field flux: 1)      Distortion in Main Field Flux 2)      Net reduction of Main Field Flux Due to the above two effects of armature mmf, there are many detrimental effects on the Electrical … Read more

Concept of Electrical and Mechanical Angles & Synchronous Speed

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Electrical and Mechanical angles are frequently used in the study of Electrical Machine theory and therefore it is very important to have a crystal clear concept of these two terms and the relationship between them. In this post we will also discuss about the Synchronous Speed and their relationship with Electrical and Mechanical angle. As … Read more