AC Compensated Series Motor
It is a specialized variation of an AC series motor featuring an extra winding referred to as a compensating winding. This component is inserted in conjunction with the current field and armature windings to counteract the transformer effect present in an unadjusted series motor.
The compensating winding is an additional component placed in the stator, alongside the field windings. It is carefully connected, as demonstrated in the accompanying diagram, to effectively address and reduce the occurrence of arcing issues.
Repulsion Motor
The Repulsion motor, known as an AC single phase motor, functions with the AC input directed solely to the field or stator windings. On the other hand, the armature windings are linked to the commutator and abruptly shorted by utilizing a pair of brushes. Notably, there exists no electrical linkage between the field windings and the armature windings, distinguishing its operational mechanism. The rotor current generation is facilitated through induction, showcasing its unique design and functionality.
The brushes are strategically designed to be easily adjustable, allowing for seamless changes in angle relative to an imaginary stator axis. This pivotal feature empowers users to effortlessly halt, initiate, and reverse the motor simply by modifying the brush angle. Moreover, adjusting the angle of the brushes enables users to conveniently control the motor's speed as desired.
As the rotor is shorted using the brushes to form a loop, a current is induced when alternating current flows in the field winding. This induced current owing in the rotor’s windings generates its own magnetic field. The direction of the magnetic field depends on the brushes' angle, determining the interaction with the stator's field. By adjusting the brushes to different angles, like 90°, 180°, or 0°, the motor can be stopped or set in motion. Rotating the brushes slightly at 20° in either direction causes the motor to rotate accordingly. The variation in the angle alters the repulsion between the stator and rotor's magnetic fields, consequently adjusting the rotor's speed.
The starting torque of this motor can also be adjusted by changing the angle of brushes to achieve peak starting torque at 45°. Initially employed for traction because of its excellent speed control, this motor has now been replaced by more advanced traction motor models.
Repulsion-Start Induction-Run Motor
The Repulsion Induction motor, also referred to as a repulsion-start induction-run motor, is a specialized adaptation of the standard squirrel cage induction motor. This motor capitalizes on the high starting torque characteristic of a repulsion motor while operating under normal conditions as a squirrel cage induction motor.
There is a special mechanism in place for the initiation and operation of the motor. At the beginning of the motor startup process, a set of shorted brushes is linked to the commutator at a specific angle, akin to the setup in a repulsion motor. As the motor gains momentum and reaches its operational speed, the mechanism raises the brushes and joins the bar together by shorting the commutator, creating a squirrel cage rotor configuration. Subsequently, the motor continues to function as an induction motor.
The benefit of the repulsion start is significant, providing 5-6 times higher starting torque compared to other induction motors. Additionally, the brushes enjoy an extended lifespan since they are solely utilized for initiating the motor. Consequently, these electric motors boast a prolonged mechanical life and demand minimal maintenance.
DC Motor
The DC motor is recognized as one of the primary types of electrical motors designed to operate solely on Direct Current (DC). Unlike AC motors, DC motors operate without phases and rely on only two wires for functionality. Being among the earliest motor innovations, DC motors boast ease of speed regulation through voltage adjustment. They feature uncomplicated mechanisms for starting, stopping, accelerating, and reversing. While the initial installation expense of a DC motor is economical, ongoing maintenance costs escalate with motor size and power amplification.
The basic working principle of DC motors is based on the Fleming’s left hand rule, which states that a current-carrying conductor inside a magnetic field experiences a force of thrust that is mutually perpendicular to each other. This fundamental concept is crucial in understanding how DC motors operate. Furthermore, DC motors can be classified into various types based on their specific characteristics and applications.
- Brushed DC Motor
- Brushless DC Motor
- Coreless or Ironless DC Motors
Brushed DC Motor
As the name suggests, direct current (DC) electric motors are equipped with brushes and commutators. These components play a crucial role in connecting a stationary circuit with a rotating circuit within the motor. In this setup, the rotor winding is energized by conductive brushes. It's important to note that brushed motors, while relatively simple and cost-effective, require regular maintenance because of the constant sliding between the brushes and the sparks they generate.
The brushed DC electric motors are further classified into
- Separately Excited Motor
- Self-Excited DC Motor
- Permanent Magnet DC Motor
Separately Excited DC Motor
This specific category of DC motors is characterized by having independent excitation. Excitation involves supplying power to the field windings, also referred to as the stator's windings. The field windings and the armature's windings are each linked to their individual power sources, ensuring distinct power supplies for both components.
In this specific setup, we have the ability to enhance the magnetic field on its own by amplifying the DC excitation level while keeping the armature current unchanged. This unique characteristic is highlighted by the fact that the armature current does not flow through the field winding.
Self-Excited DC Motor
Such type of brushed DC motors is known for their self-exciting field windings, which are directly connected to the armature windings. With a single power source energizing both windings, there is no need for a separate excitation source. Additionally, the field windings can be arranged in series, parallel, or a partly series configuration with the armature windings, resulting in various classifications of self-excited DC motors.
- Series Wound
- Shunt Wound
- Compound Wound
Series Wound DC Motor
In a series wound DC motor, the field winding is connected in series with the armature windings, creating a setup where the current passing through the field windings precisely aligns with the current flowing through the armature windings. This configuration allows for a direct relationship between the two sets of windings, resulting in synchronized current flow throughout the motor system.
The speed of electric motors fluctuates in response to changes in the connected load, showcasing the adaptability of these devices.
Shunt Wound DC Motor
Such direct current (DC) motors are designed with the field winding, also referred to as the shunt field winding, connected in parallel with the armature winding. This configuration ensures that the field winding receives the full terminal voltage, maintaining equal voltage across both windings. Consequently, the supplied current is split into field current and armature current, enabling efficient operation of the motor.
Such electric motors are preferred for applications requiring a consistent speed as they are able to maintain a steady speed even when subjected to various connected loads. The shunt winding, which consists of windings connected in parallel, plays a crucial role in achieving this functionality.
Compound Wound DC Motor
The compound wound DC motor is designed to harness the advantages of both series wound and shunt wound DC motors by merging the characteristics of parallel and series winding configurations in both the field and armature windings. This unique combination allows for the classification of compound wound motors into two distinct types based on the specific winding structures they employ.
- Cumulative compound
- Differentially compound
Cumulative Compound
When the shunt field and the series field windings generate flux in the same direction, the shunt field’s flux aids in boosting the main series field flux. This configuration characterizes a cumulative compound wound motor, where the total flux produced is consistently higher than the initial flux.
Differentially Compound
When the shunt field and the series field windings generate flux in opposite directions in a differentially compound DC motor, their effects cancel out, resulting in reduced overall flux. This type of motor is not commonly used in industrial applications due to its limited practicality. Short shunt and long shunt DC motors are variations of compound motors, distinguished by the arrangement of their windings. More details on short shunt and long shunt DC motors are provided below for a better understanding.
Short Shunt DC Motor
A motor is classified as a short shunt DC motor when the shunt field windings are connected in parallel to the armature windings while being in series with the field windings. This configuration, illustrated in the figure below, is alternatively referred to as a compound wound motor.
Long Shunt DC Motor
A DC motor is classified as a long shunt motor when the shunt field windings are connected in parallel to both the armature winding and the field winding in the motor setup.
Comments
Post a Comment