Types of DC Motor

A direct current motor ( DC Motor) is a machine that converts direct electrical energy into mechanical energy by varying winding and magnetic field configurations to achieve desired operating characteristics. 

There are four major type of DC Motor

• Series DC Motor
• Shunt DC Motor
• Compund DC Motor
• Parmanenet Magnet DC Motor

Classification of DC Motor

Based on types of construction and electrical connections, DC motors can be categorized below:

• Permanent Magnet DC Motor
• Shunt Motor
• Serioes Motor
• Compund Motor
• Short Shunt Motor
• Long Shunt Motor
• Differentially Compound
• Cumulatice compound

Permananetr Magnet DC motor

Permanent Magnet A DC motor uses a strong magnet attached to the yoke to maintain a constant magnetic flux. These are used in automobile starters, wipers, air conditioners, and more. To generate more power, these DC motors frequently use powerful magnets made of rare earth alloys such as neodymium. 

Shunt DC Motor

The field is connected to the armature winding in parallel, also known as a shunt. The shunt field can be excited separately from the armature windings, allowing for more precise speed regulation and simple reverse control.

Series DC Motor

A large wire carrying the entire armature current winds the field in a few turns. These are not the best choice for variable-speed applications. This is useful for applications that require large starting loads, such as traction, cranes, and other heavy machinery. These motors generate a lot of starting torque, but their speed cannot be controlled. If they are run without any load, they may sustain damage.  A series motor's speed is proportional to its load, so as the total current flowing through the circuit decreases, the speed increases.

Compund DC Motor

These have a shunt field that is evidently excited. A compound DC motor has two sets of field winding on each magnetic pole, one in series and the other to the armature winding. They have a good starting torque but may have issues in variable-speed applications. 

Compund DC motors are dividing into two types

• Short Shunt Compund DC Motor
• Long Shunt Compound DC Motor

Short Shunt DC Motor

The shunt field winding is only connected to the armature winding, and too in parallel. The field coil, which is in series, is completely exposed to current before being separated into the armature. 

Long Shunt DC Motor

The shunt field winding is connected in parallel with both the series field coil and the armature, which are then connected in series. 

Differentially Compound DC Motor

In a DC compounded motor, the shunt field winding is designed to reduce the effect of the main series winding flux. 

Cumulative compund DC Motor

The flux produced by the shunt field winding amplifies the effect of the main field flux produced by the series winding. 

Related Article:

1. Part of DC Motor

Parts of a DC Motor

A direct current motor (DC motor) is an electrical device that converts electrical energy to mechanical energy. A DC motor's input electrical energy is direct current, which is converted into mechanical rotation. In this session, we'll learn about DC motors and their different parts and applications.

Different parts of DC Motor

Following are the main parts of DC motors:

Stator 

The stator is the stationary part of the DC motor, and its primary function is to generate the magnetic field. The stator consists of two or more magnetic poles. The stator established two poles, north and south poles, which interact with the rotor to produce torque. These poles are made up of either permanent magnets or electromagnets. The stator consists of field winding. The field windings are wound around the stator poles. When current flows through these windings, it generates a strong magnetic field that interacts with the rotor, causing movments. Field windings are connected in series or parallel with the motors. 

Rotor

The rotor is the dynamic portion of the DC motor that is also called an armature. It consists of a cylindrical core made up of laminated steel. In this motor, different slots are made at the core of the rotor to accommodate the windings.  These windings are made of copper wire and are wound into the slots of the rotor's core. When current flows through these windings, it generates a magnetic field around the rotors, which interacts with the stator and causes rotational movement. 

Commutator

The communtator is another imrptoatn part of the DC motor. It is made up of hard drawn copper segments that have been mica insulated. The priamry function of commutaor is to deliver electrical current to the aramature windiing. It is a split ring device that is connected to the aramature windiing ad rotates with them. When the armature crosses a magnetic pole, the current throungh the windiing are reverses ad the motors torwue is maintained. This reversal of the current keep force applied to the rotor in the same direrction, ensuring smooth rotation.

Brushes

DC motor brushes are made of graphite and carbon and serve to transfer current from an external power source to the commutators. Brushes are mounted on the motor housing and make sliding contact with the commutator. As a result, we conclude that the commutator and brushes are responsible for transmitting power from the static current to the mechanically rotating region or rotor. Brushes wear out over time due to friction with the commutator and must be replaced frequenlty. It also generates noise and causes power losses. Regular inspection for wear and tear as well as clening to remove debris or dust build up  can have a significant impct on the motor's effiecinecy. 

Armature

When examining a DC motor, the armature is a critical component that converts electrical energy into mechanical motion. Armature construction is a critical aspect that directly impacts the motor's efficiency and performance. Typically armatures have a core made of thin, insulated metal sheets that are stacked to form the armature's body. This construction allows for the creation of a magnetic field essential for the motor's operations. 

The torque, speed, and overall functionality of a motor are heavily influenced by its armature's winding techniques. The winding process involves wrapping copper wire around the armature core to form multiple coils that strengthen the magnetic field. The number of windings, wire gauge, and winding pattern all have a significant influence on the motor's charcteristics. Engineers can tailors the motor to specific requirements by carefully selecting the appropriate winding technique, resulting in optimal performance in a variety of applications. 

Applications of DC motors

Shunt DC Motors

• Centrifugal and reciprocating pumps
• Lathe machines
• Blowers and fans
• Drills
• Fans
• Windscreen wiper drives
• Machine tools
• Milling machines

Series DC Motors

• cranes
• Conveyors
• Hoist
• Elevators
• Power tool
• Hair dryers
• Winching systems
• Electric locomotives

Compound DC Motors

Rolling mills

Presses

Heavy planner

stamping machines

Conveyers

Compressors

Related Articles:

1. Types of DC Motor

Universal motor | Characteristics | Constriction | Applications |

The universal motor is a special type of motor that is created to operate with almost the same features as AC as well as DC power. Commutator machines are used in universal motors.

• Universal motors powered by single-phase alternating current work at speeds ranging from 3000 to 2500 rpm and have a power rating of up to 1200 watts.
• Their speed rotation is only limited by the mechanical strength of the rotor and bearings as well as the usable brush lifespan.
• Universal motors are used in portable tools and different types of equipment.
• The structure of the universal motor is similar to the exactly to the DC motor. 

Characteristic of universal motor

• The universal motor is much less expensive.
• The universal motor has a high changeable speed.
• A universal motor's speed is low at full load and very high at no load. The motor is operational.
• This motor has a high changeable speed.
• It is a single-phase series motor.
• These motors are very portable.
• The motor generates a lot of transmitting torque.
• This motor is a type of commutation motor.
• Universal motor work with high efficiency in DC supply.
• The universal motor produces a unique wiring sound when operational.
• It runs at a lower speed when using an AC supply due to a voltage drop in reactance.
• A universal motor at full load about 90% of the power factor

This unique characteristic of the universal motor of being able to operate at all types of voltage makes it universal.

Speed/load characteristics of universal motor

Speed/load characteristics of the universal moor are similar to that DC series motor. The speed of a universal motor is low at full load and the highest at no load. Gear trains are made use of to get the required speed at the required load. The speed/load characteristics for both AC as well as DC supply are shown in the figure below.

Speed/load Characteristics 

Construction of universal motor

The construction of a universal motor is very similar to the construction of a DC machine. A stator is mounted on which field poles are attached. Field coils are would on the field poles. Still, the whole magnetic ath is laminated. when operating on AC, lamination is required to minimize eddy current.

Stator

A stator is a part that does not move. It is a stationary part, which contains the following components

• Field coils
• Laminated case
• Wiring from source
• Brushes

Rotor

The rotor is a rotating part, it consists of the following main part

• Shaft
• Commutator
• Rotor windings

Commutator

Commuters work like a reverse the direction of current in the rotor and external circuit. So we make sure that the current flowing through the rotor winding is always in the same direction.

Brushes

These are the components of the stator that help in the passage of current to the rotor, or moving section, of the universal motor. Brushes are often produced from graphite.

Frame

the frame is built of steel or rolled iron shells. It is in charge of keeping the magnetic field and motor body laminations in good condition.

Working of universal motor

A universal motor can be powered by a direct current (DC) or a single-phase alternating current(AC) source. When a DC supply is connected to the universal motor, it operates as a DC series motor. An electromagnetic field is created when electricity travels through the field winding. The same current runs through the armature conductor as well. When a current-carrying conductor is placed in an electromagnetic field, it experiences a mechanical force. As a result of this mechanical force, or torque, the rotor begins to rotate. The direction of this force is determined by the burning left-hand rule.

When creates unidirectional torque powered by an alternating current supply. Because the armature and field windings are linked in series, they are in the same phase. As a result as the polarity of AC changes regularly, the reaction of current in the armature and field winding reverses at the same time.

As a result the direction of the magnetic field and the direction of armature current reverse, while the direction of force experienced by armature conductors stays constant. Thus, regardless of whether the power source in AC or DC universal motors operates on the same principles as DC series motors.

Application of universal motor

• Universal motors are found in portable drills, blenders, and other similar devices.
• They are commonly seen in portable drill machines.
• Polishers, blowers, food mixers, vacuum cleaners, and kitchen equipment all use them.
• Table fans, hairdryers, and grinders all employ universal motors.

Advantages of Universal motor

• The cost of the motor is higher than ordinary brushed and quite less than brushless.
• The main advantage of a universal motor is it is lightweight.
• It is simple design and cheap.
• It is very high speed.
• It is easy to construct and inexpensive.
• It is smaller in size allows it to be used in the smallest device.
• In universal motors, the main parts are quite durable.
• They are capable of generating a high number of revolutions.
• The universal motor is ideal for small appliances that require high power.
• The cost of a universal motor is a little higher than an ordinary brushed one and quite less than a brushless one.

Disadvantages of Universal motor

• Speed control is lousy.
• It is not easy to reverse the motor.
• The efficiency range of 55-80% and it depends on source type.
• The universal motor has a high maintenance cost and short life commutator.
• When working with voltages up to 100 V.s, the efficiency drops dramatically.
• Universal motors produce more noise and vibration than induction motors.
• This motor is in direct contact with the brushes with the collector, they require periodic replacement or repair.

Summary

In this article, you will understand the details of the universal motor and its characteristics, construction, working principles, Speed, load characteristics, advantages, disadvantages, and applications. So we all understand that universal motors run at very high speeds at no load, which is quite dangerous. Also this article we also discuss that this type of motor is unique its power is dependent on both AC and DC.

Explore more information:

1. Synchronous motor
2. Why are induction motors widely used in the industry
3. Difference between synchronous and asynchronous motor
4. Difference between induction motor and synchronous moto

Synchronous motor

As an electrical, the electrical motor is an electro-mechanical device that converts electrical energy into mechanical energy.  

What is a synchronous motor?

The definition of the synchronous motor states that, An AC motor in which at steady state, rotation of the shaft is in sync with the frequency of the applied current. The synchronous motor works as an AC motor but here the total number of rotation made by the shaft is equal to the interference multiple of the frequency of the applied current.

Working principle of synchronous motor

• The synchronous motor will work on the basic principle of magnetic locking.
• When two unlike strong unlike magnets poles are brought together in the motor. There exists a tremendous force of extraction between those two poles. In such a condition, the two magnets said to be magnetically locked. 
• The stator and the rotor are two main parts of the synchronous motor. The stator is the stationary part of the motor while the rotor is their rotating part. The stator excited by the three-phase supply, and the rotor is excited by the DC supply. 
• The term excitation means the magnetic field induces in the stator and rotor both of the motor. The main aim of the excitation is to convert the stator and rotor both into an electromagnet.

The three-phase supply induces both the north and south pole on the stator. The three-phase supply is sinusoidal. The polarity of their wave changes after every half cycle and because of this reason the north and south pole also varies. Thus the rotating magnetic filed develop on the stator.

The magnetic field develops on the rotor because of we have to apply DC supply. The polarity of the DC supply becomes fixed and no change in polarity, and thus the stationary magnetic field develops on the rotor. The term stationary means their north and south pole remain fixed.

 Synchronous Motor

The speed at which the rotating magnetic field that rotates is known as the synchronous speed. The synchronous speed of the motor  N depends on the frequency of f the supply and the number of poles of P  the motor. 

Nₛ =  120f/P

f =  The supply frequency in Hz

P = The number of poles

N = synchronous speed in RPM

When the opposite pole of the stator and rotor face with each other, the force of attraction occurs between them. The attraction force develops the torque in the clockwise direction. The torque is the kind of force that moves the object in the rotation. Thus the poles of the rotor dragged towards the pole of the stator.

After every half cycle, the pole on the stator is reversed direction. The position of the rotor will remain the same because of some inertia. The inertia is the tendency of an object to remain fixed in one direction. When the pole of the stator and rotary face each other, the force of repulsion occurs between them and the torque develops in the clockwise direction.

Main features of synchronous motor:

• Synchronous motor is inherently not self-starting. They require some external means to bring their speed close to synchronous speed before they are synchronized.
• In constant supply frequency, they behave as constant speed motor irrespective of load condition.
• This motor has the unique characteristics of operating under any electrical power factor. This makes it is used in electrical power factor improvement.
  

Application of synchronous motor:

• Power factor correction 
• Reciprocating pump
• rolling mills
• Voltage regulation
• Constant speed
• Constant load drives.

• Explore more information:

1. Working principle of synchronous motor
2. Universal Motor
3. Types of synchronous motor
4. Why are induction motors widely used in the industry
5. Difference between synchronous and asynchronous motor
6. Difference between induction motor and synchronous motor