Inductive loads are induction furnace, single induction phase motor, three-phase motor etc. Resistive loads are water heater, room heater etc. AC Motor Loads ( Alternating current) :ĪC loads consist of resistive loads, inductive loads.
THREE PHASE MOTOR WINDING MACHINE FULL
Hence, Operating a machine below full load current increases the life span of the electrical equipment. Due to the excess current flow, the machine produces additional heat (Because of P=I 2 * R)., This may lead to damages to the insulation or winding of the electrical equipment. The input current to the machine exceeds the full load current means, the electrical machine may get damage. What is Full Load Current:įull Load Current is nothing but a maximum allowable current. The full load current is used to design the protection system for the electrical equipment. Cylindrical-rotor synchronous generators are called turbo-alternators or turbo-generators.Full Load current calculation of AC and DC machine: Steam or gas turbines drive Cylindrical-rotor machines. Thus, the cylindrical rotors are useful in high-speed machines. Such construction limits the centrifugal forces. These machines have a small diameter and long axial length. The unslotted portion of the rotor forms two pole faces. The d.c field windings are connected in these slots. In about two-thirds of the rotor periphery, slots are cut at regular intervals and parallel to the shaft. These rotors are made up from solid forgings of high-grade nickel-chrome-molybdenum steel. It has no physical poles as in the salient-pole construction. The construction of the rotor is such that it forms a smooth cylinder. Cylindrical RotorĬylindrical-rotor machines are also known as non-salient pole rotor machine. Salient-pole alternators that are driven by water turbines are called hydro-alternators or hydro generators. The salient-pole generators have a large number of poles and lower operating speed. The end of the field windings is connected to a d.c winding by the brushes on the slip-rings. To give the alternate north and south polarities, the individual field-pole windings are connected in series. This will help the machine to generate sinusoidal e.m.f. The pole faces are so shaped that the radical air gap length increases from the pole center to the pole tips so that the flux distribution in the air gap is sinusoidal. The air gap is minimum under the pole centers, and it is maximum in between the poles. A non-uniform air gap accompanies a salient-pole synchronous machine. Salient-pole rotors have faces to damp out the rotor oscillations during a sudden change in load conditions. After the field coil is placed around each pole body, these poles are fitted by a dove-tail joint to a steel spider keyed to the shaft. Identical dimensions poles are assembled by stacking laminations to the required length and then riveted together.
The rotor is subjected to changing magnetic fields that is why it is made of steel laminations to reduce the eddy current losses. These are used for the rotors for four or more poles. A salient-pole consists of poles that are projected out from the surface of the rotor core. When current flows in a distributed winding it produces an essentially sinusoidal space distribution of e.m.f. The winding is star connected and is distributed over several slots. A 3-phase winding is put in the slots cut on the inner periphery of the stator. To reduce the hysteresis and eddy current losses, the stator core is assembled with high-grade silicon content steel laminations. The frame of the stator is made up of cast iron for a small-size machine, and welded steel for large size machines. The parts of the stator are the frame, stator core, stator windings, and cooling arrangement.
The rotor of the machine produces the main flux. The stator carries the armature winding in which the voltage is generated, and the output is taken from it.
The stator is the stationary part of the machine, and the rotor is the rotating part of the machine. Next → ← prev Construction of three phase synchronous machinesĪn alternator consists of two parts, the stator, and the rotor.
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