Skip to main content

INDUCTION REGULATORS

An induction regulator is essentially a constant voltage transformer, one winding of which can be moved w.r.t. the other, thereby obtaining a variable secondary voltage. The primary winding is connected across the supply while the secondary winding is connected in series with the line whose voltage is to be controlled. When the position of one winding is changed w.r.t. the other, the secondary voltage injected into the line also changes. There are two types of induction regulators viz. single phase and 3-phase.

1. SINGLE-PHASE INDUCTION REGULATOR

A single phase induction regulator is illustrated in Figure1, In construction, it is similar to a single phase induction motor except that the rotor is not allowed to rotate continuously but can be adjusted in any position either manually or by a small motor. The primary winding AB is wound on the stator and is connected across the supply line. The secondary winding CD is wound on the rotor and is connected in series with the line whose voltage is to be controlled.

Figure1: Single phase induction regulator
The primary exciting current produces an alternating flux that induces an alternating voltage in the secondary winding CD. The magnitude of voltage induced in the secondary depends upon its position w.r.t. the primary winding. By adjusting the rotor to a suitable position, the secondary voltage can be varied from a maximum positive to a maximum negative value. In this way, the regulator can add or subtract from the circuit voltage according to the relative positions of the two windings. Owing to their greater flexibility, single phase regulators are frequently used for voltage control of distribution primary feeders.

2. THREE-PHASE INDUCTION REGULATOR

In construction, a 3-phase induction regulator is similar to a 3-phase induction motor with wound rotor except that the rotor is not allowed to rotate continuously but can be held in any position by means of a worm gear. The primary windings either in star or delta are wound on the stator and are connected across the supply. The secondary windings are wound on the rotor and the six terminals are brought out since these windings are to be connected in series with the line whose voltage is to be controlled.
Figure2: 3-phase induction regulator
When polyphase currents flow through the primary windings, a rotating field is set up which induces an EMF in each phase of rotor winding. As the rotor is turned, the magnitude of the rotating flux is not changed; hence the rotor EMF per phase remains constant. However, the variation of the position of the rotor will affect the phase of the rotor EMF w.r.t. the applied voltage as shown in Figure3. The input primary voltage per phase is Vp and the boost introduced by the regulator is Vr. The output voltage V is the vector sum of Vp and Vr. Three phase induction regulators are used to regulate the voltage of feeders and in connection with high voltage oil testing transformers.

Comments

Post a Comment

Popular posts from this blog

ADVANTAGES AND DISADVANTAGES OF CORONA

Corona has many advantages and disadvantages. In the correct design of a high voltage overhead line, a balance should be struck between the advantages and disadvantages. ADVANTAGES (i) Due to corona formation, the air surrounding the conductor becomes conducting and hence virtual diameter of the conductor is increased. The increased diameter reduces the electrostatic stresses between the conductors. (ii) Corona reduces the effects of transients produced by surges. DIS-ADVANTAGES (i) Corona is accompanied by a loss of energy. This affects the transmission efficiency of the line. (ii) Ozone is produced by corona and may cause corrosion of the conductor due to chemical action. (iii) The current drawn by the line due to corona is non-sinusoidal and hence non-sinusoidal voltage drop occurs in the line. This may cause inductive interference with neighboring communication lines.
Read more

ADVANTAGES OF PER UNIT SYSTEM

PER UNIT SYSTEM The per-unit system expressed the voltages, currents, powers, impedances, and other electrical quantities basis by the equation: Quantity per unit (pu) = Actual value/ Base value of quantity ADVANTAGES OF PER UNIT SYSTEM While performing calculations, referring quantities from one side of the transformer to the other side serious errors may be committed. This can be avoided by using per unit system. Voltages, currents and impedances expressed in per unit do not change when they are referred from one side of transformer to the other side. This is a great advantage. Per unit impedances of electrical equipment of similar type usually lie within a narrow range, when the equipment ratings are used as base values. Transformer connections do not affect the per unit values. Manufacturers usually specify the impedances of machines and transformers in per unit or percent of name plate ratings. Transformers can be replaced by their equivalent series impedances. ...
1 comment
Read more

ABSOLUTE AND SECONDARY INSTRUMENTS

The various electrical instruments may, in a very broad sense, be divided into (i) Absolute Instruments (ii) Secondary Instruments. Absolute Instruments are those which give the value of the quantity to be measured, in terms of the constants of the instrument and their deflection only. No previous calibration or comparison is necessary in their case. The example of such an instrument is tangent galvanometer, which gives the value of current, in terms of the tangent of deflection produced by the current, the radius and number of turns of wire used and the horizontal component of earth’s field.  Secondary Instruments  are those, in which the value of electrical quantity to be measured can be determined from the deflection of the instruments, only when they have been pre-calibrated by comparison with an absolute instrument. Without calibration, the deflection of such instruments is meaningless. It is the secondary instruments, which are most generally used in ev...
Post a Comment
Read more