What is a salient pole rotor?

Salient pole rotor includes a large number of exposed poles mounted on a magnetic wheel. The construction of a bright pole is as shown in the image on the left. The proposed poles are made of metal laminations. The rotor winding is provided on these poles and is supported by pole shoes.

Pole rotors have a wide width and short axial length. They are usually used in low-speed electric machines, say 100 revolutions per minute (RPM) to 1500 RPM. As the rotor speed is low, a large number of poles are needed to obtain the required frequency. On average, the number of sharp pole generators is between 4 and 60.

Flux distribution is poor compared to a non-uniform salient pole rotor, which is why the manufactured emf (electromotive force) waveform is not as good as a cylindrical rotor. Pole rotors usually require winding dampers to prevent rotation of the rotor during operation.

Working principle of salient pole rotor

In a three-phase input machine, the alternating current supplied to the stator windings empowers it to create a rotating magnetic flow. The flux produces a magnetic field in the air space between the stator and the rotor and introduces a voltage that generates current energy through the rotor bars. The rotor circuit is short and current flows to the rotor conductors. The action of rotating flux and steel generating power generate torque to start the engine.

The alternator rotor is made of a wire coil covered with a metal core. The magnetic part of the rotor is made of stainless steel to help seal the driver's spaces to a specific shape and size. As the currents travel through the wire coil, a magnetic field is created around the core, called the current field. The current strength of the field controls the energy level of the magnetic field. Direct current (DC) drives the current field in one direction and is delivered to the telephone coil with a set of brushes and smoothing rings. Like any magnet, the magnetic field produced by the pole is north and south. The normal direction of the clock powered by a rotor-powered engine can be adjusted by using magnets and magnetic fields embedded in the construction of the rotor, allowing the engine to run backward or counterclockwise.

Salient pole synchronous generator

The salient pole synchronous generator is separated by a circular saw blade with the construction features of the field poles operating through a large interpolar wind gap. This type of construction is commonly used in machines associated with low-speed hydraulic power engines so that the salient pole synchronous generator has multiple pairs of different poles in machines connected to high-speed steam engines (3,000/1,500 rpm) and two or four-pole structures. Analysis of the salient pole synchronous generator is performed with the two reaction responses.

In a circular rotor machine, the armature current in the phase with an extended field or quadrature (90°) to force produces the same flux connection per ampere as the air gap is the same so that the armature reaction is given in the category or quadrature current is the same. In a pole machine, the air gap is not the same as the rotor periphery. It is very small near the axis of the main poles (called the vertical axis) and the largest near the interpolar region axis (called the quadrature axis). Armature current in the quadrature with a force that produces fluctuations near the vertical axis and doubts of flow (due to a small air gap), produces greater flux contact per ampere, and hence, the machine produces a larger armature reaction called direct axial length reactance (X_d) in the quadrature Id phase flow of armature current I_a .

On the other hand, the armature current in phase with the force produces fluctuations near the axis of the quadrature and fluctuations of the flux path to the surface (due to the large interpolar air gap), producing small flux connections per ampere. Hence, the machine produces a small arms reaction, X_q reaction (quadrature axial length reactance <X_d) in the flow of the phase of armature current (I_a).

Operating salient pole synchronous generator

Since the key beam machine provides a different reaction to the movement of the parts of the current arm, the circuit model cannot be designed. When choosing a large generator, in addition to the limited mega-volt ampere and power factor, the most suitable stator and rotor currents should be considered as it influences mechanical stress and temperature rise. Such restrictions on employment are set by the worksheet or worksheet.

For ease of analysis, the effects of space-filling, durability, saliency, and resistance are ignored and an incomplete number of concurrent responses are considered. Salient pole synchronous generators such as turbines are widely used in power plants.

Synchronous machines

The synchronous machine integrates both compatible motors and compatible generators. The alternating current (AC) system has some advantages over the DC system. Therefore, the AC system is only used to generate, transmit, and distribute electricity. A machine that converts mechanical energy into AC power is called a synchronous generator or alternator. However, if the same machine can work as a car, it is known as a synchronous motor.

If the synchronization device fails, and if the connections are short-circuited, the motor will fail to maintain a moderate speed, also the machine will not develop enough torque to maintain its rotation and will stop. The engine is then removed from the step.

In the case where the synchronization machine operates as a generator, you must operate at a constant speed called synchronous speed to generate power at a specific frequency. In some countries, the frequency range is 50 hertz.

A synchronous machine is an electromechanical transducer that converts mechanical power into electrical energy or vice-versa. The basic thing or law that makes this change happen is known as the Electricity Importation law and the Interaction law.

Context and Applications

This topic is important for professional exams in both graduate and postgraduate studies and in particular:

• Bachelors in Electrical Engineering
• Masters in Electrical Engineering

Practice Problems

Q1. In which of the following the separate damper winding is used?

Answer: Option b

Explanation: Separate damper winding is used in salient pole-type rotors.

Q2. In salient pole machines which of the following is least at the center and increases while moving away from the center?

Answer: Option c

Explanation: In salient pole machines, the air gap is least at the center and increases while moving away from the center.

Q3. Which of the following is used as prime movers to drive projected pole-type alternators?

Answer: Option c

Explanation: Internal combustion engines are used as prime movers to drive projected pole-type alternators.

Q4. From which of the following the poles are projected out from the surface of the rotor?

Answer: Option a

Explanation: Salient pole-type rotors have poles that are projected out from the surface of the rotor.

Q5. What amount of rotation should be provided to the resultant flux for half cycle of fluxes in a synchronous motor?

Answer: Option d

Explanation:  For a half cycle of fluxes in a synchronous motor, 180 degrees should be provided to the resultant flux.