This is a comprehensive study on the DC shunt motor and I will share its functions and other features.
Electric motors have offered us practically every contemporary convenience by allowing us to transfer electrical power into physical motion. These machines have assisted us in creating marvels such as automobiles, computers, and air conditioning, to mention a few. It is all due to the diversity of electric motors accessible in the industry. The DC motor is one of our oldest and most extensively used designs.
This essay will focus on one specific DC motor, the DC shunt motor. The DC motor was one of the first electric motors developed to transfer direct current electrical energy to mechanical energy. It is one of the finest gadgets ever made by humanity, and it has completely transformed our lives since then. There are numerous different types of this rotating electrical machine, all of which have almost identical parts that work together depending on whether an electronic or electromechanical mechanism is in charge of changing the direction of current in the motor.
What exactly is a DC motor, and how does it work?
Because the shunt DC motor is essentially a brushed DC motor, it is necessary first to explain the fundamental concepts that apply to all of these designs.
Figure 1:
All DC motors have two major components: a stator (external housing with stator field) and a rotor (spinning component) (the rotating component connected to the DC power source). The stator field can be constructed of natural permanent magnets or a wire winding (or “field winding,” as seen in Figure 1), creating a steady magnetic field across the rotor assembly. The armature, armature windings, output shaft, commutates, and brushes make up the rotor. The armature winding is the coil of wire that wraps around the output shaft and is guided by the armature itself or metal lamination.
These armature windings finish at the commutator rings, which are mechanically isolated from the DC power supply (they “hover” over the output shaft, waiting to be pushed by the brushes). By latching onto the commutator rings when the motor is turned on, the bushes complete the circuit shown in Figure 1 and enable current to flow via the brushes, commutator rings, and armature windings. When this happens, the armature generates an electromagnetic field that resists the permanent stator field. Because the rotor is free to rotate, the interplay of these two fields results in the rotation of the output shaft and, as a result, usable speed/torque.
DC Shunt Motors: Functions of DC Shunt Motor
Now that we’ve covered the fundamental concepts that apply to all DC motors, let’s look at the specific configuration found in the shunt DC motor, as illustrated in Figure 2:
The field winding, which generates the constant magnetic field in the stator, is connected to the armature windings in parallel or shunt in shunt DC motors. The armature and field windings are both powered by the same power source, and the total current is split into two “parallel” channels.
In shunt DC motors, the field winding is constructed up of multiple windings of thin wire to both strengthen the magnetic field and restrict the current through the coil. As a result, the wind is lowered via the field coil while increasing in the armature (remember, the draft is shared when in parallel). Back EMF – an electromotive force created by the armature’s magnetic field rotating through the stator field – is produced by the higher current in the armature and lessens the draft through the armature winding.
This back EMF increases when the motor speed increases (since it is related to speed) and drops if the armature rotation slows, owing to increased stress on the shaft. DC Shunt motors can self-regulate their speed, particularly when a more significant load is applied to the post. This is why they are commonly known as constant-speed motors. Hence, shunt motors have low beginning torque but consistent speed; this is the converse of series DC motors, which have excellent starting torque but almost no speed regulation (review our article about series wound DC motors for more information). They are also reversible by simply switching the polarity of the armature or field coils.
Specs for DC Shunt Motors:
Understanding what values to look for when selecting a shunt DC motor is helpful. This article will go through some typical specs to check for but remember that most spec sheets contain considerably more information than what is offered here.
Field Voltage/Armature Voltage:
Parallel connection of the armature and field windings results in a dual voltage supply for each part (not across the complete circuit, though; remember, they share the same power source). Because of this, shunt DC motor specifications often provide two rated voltages, one for each coil. For instance, a shunt motor may have an armature voltage of 440 V with a maximum of 600 V and a field voltage of 220 V with a maximum of 500 V. These values are affected by the frame size and motor construction. Additionally, a DC motor should only be used with a power supply of at least its rated voltage since this affects performance and might cause overheating.
Basic Speed & Power:
Because these motors are considered constant speed, the spec sheet typically includes a base speed and a corresponding power (in HP or kW). These characteristics describe what the motor is capable of moving and how quickly it is capable of doing so; nevertheless, DC shunt motors have the ability to adjust speed even when the load changes (within safe tolerances).
Dimensions of the frame:
NEMA has established standard frame sizes to facilitate customer replacement between motor suppliers. However, the motor’s dimensions are always provided if not standardized. The frame size gives the specifier an indication of the engine’s potential power and potential for utilization in a particular application (though size can be misleading with electric motors, so use caution).
The Life of a Brush:
Brushes deteriorate naturally with time in shunt DC motors because they link the power supply to the spinning armature. Most DC motors provide a brush life that is in hours, so operators can track how long the brushes have been used and when they need replacement. Therefore, it is critical to maintaining these motors by replacing the meetings as required. Otherwise, they will become damaged or ineffective.
Criteria for Application and Selection:
Because of their feedback architecture, shunt DC motors outperform series DC motors in constant-speed applications. They can maintain a precise RPM and torque even under variable load situations, making them suitable for woodworking tools, grinders, or any other rotating power tool where a user pushes against rotation. However, because these motors have a limited beginning torque, they cannot be coupled to a substantial load at startup and must be utilized at rated speed. They also endure a minor decrease in speed when highly loaded, as no electric motor operates under perfect conditions and all experience losses.
Different types of DC shunt motor
We examined what a DC motor accomplishes and why it was created in the previous section. Subsequently, we briefly touched on its general operation. As previously mentioned, several subcategories of this type of motor are the most frequently utilized: series, shunt, permanent magnet, brushless, and compound DC motors—considering that we covered each of these categories of DC motors in a separate post. Therefore, we shall only briefly mention them for recollection in the following paragraphs.
Magnet permanent motors:
PMDC motors, sometimes referred to as permanent magnet motors, are a type of DC motor that creates a field flux using a permanent magnet. This class of DC motors has excellent speed management and starting torque. Appliances with low horsepower often employ permanent magnet motors because of their restricted torque.
Switch Motors:
The armature windings are linked in parallel with the field of shunt motors. The ability to excite the shunt field independently of the armature windings allows for excellent speed regulation with this type of motor. Shunt motors also offer streamlined controls for reversing.
Sets of Motors:
A field coil with a few rounds of wire that carries the armature current makes up a series motor. Series motors provide significant beginning torque, much like permanent magnet motors do. Series motors, however, cannot control speed as permanent magnet motors can. In addition, running series motors without a load can be pretty dangerous. Due to these constraints, series motors are inappropriate for applications requiring variable-speed drives.
Motor Compounds:
Compound motors feature a shunt field energized independently, like shunt DC motors. Compound DC motors have some issues with speed regulation in variable-speed drive applications, but they are similar to permanent and series motors in terms of providing a decent beginning torque.
An Explanation of the Operating Principle of DC Motors:
It will be simpler to comprehend the foundation and principles on which these motors operate now that we are familiar with the function and the most common varieties of DC motors. DC motors operate on the electromagnetic theory that Faraday initially proposed. According to Faraday’s principle of electromagnetism, a current-carrying conductor experiences a force when it is exposed to a magnetic field+. But, on the other hand, the conductor always moves perpendicular to the current and magnetic field, as Fleming’s Left-Hand Rule states.
These motors are relatively simple to install and can function with speed controls. They are commonly found in power above tool uses and automotive windshield wipers, car windows, computer fans, and other similar applications. DC Shunt motors do not falter when creating mechanical output, offering users control over the raw output power, but not being as robust as their series-wound counterparts.
We must be aware of every aspect of the structure if we want to comprehend the operation of a DC motor. The stator is the stationary component of the permanent electromagnet that interacts with the spinning armature’s magnetic field. The armature is the part of the magnet that spins between the north and south poles. The DC supply is linked to the armature coil, which includes brushes and a commutator. The brushes transfer this current from the spinning portion of the motor to the external load, which is stationary, after the commutator converts the AC induced in the armature into DC.
Advantages and Disadvantages of DC Shunt Motors:
DC motors are available in a variety of diameters and sizes to meet a variety of requirements. Smaller ones may be found in toys, tools, and household appliances. In comparison, bigger ones can be found in elevators and hoists, as well as in the propulsion of electric vehicles and industrial equipment.
Although AC motors have reduced the selling quantity of DC motors due to easy generation and transmission with lower losses over long distances, requiring less maintenance, and being able to work in explosive atmospheres, DC’s are still employed when AC’s cannot meet the demands. This is because DC motors have distinct characteristics and applications that compensate for many of the benefits AC motors have over them.
Advantages of DC Shunt Motor:
- The DC motor’s power supply is, in any case, inexpensive.
- The shunt motor would be able to run at a predetermined speed.
- A DC shunt motor’s speed is sufficiently constant.
- Direct current machines are suitable for heavy industrial applications with a wide range of torque and acceleration.
Disadvantages of DC shunt motor:
- Dc motors are unreliable at low rates.
- Dc motors are more significant than alternate current motors.
- DC machine installation is more costly than other forms of machine installation.
- Shunt motors are constant-speed motors, which have drawbacks when variable-speed operation is required.
- Its beginning torque is lower than that of a DC series motor for the same current input.
Conclusion:
We have provided you with essential and detailed information on the operational principles of DC motors. First, we discussed the development and construction of DC motors, their functions, and the overarching goal for which they were initially conceived. In addition, we presented some fundamental bits of knowledge about the various types of DC motors to facilitate a deeper level of comprehension. Eventually, we got to the part where we discussed the operation principle and the functions this kind of motor may perform. After this article, we summarized some of this type of motor’s benefits, drawbacks, and drawbacks. Finally, we also discussed the typical applications for this type of motor.
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FAQs:
What applications do DC shunt motors work best for?
Applications where a consistent speed and high torque are necessary include paper production facilities, lathe machines, centrifugal pumps, fans, lifts, spinning machines, blowers, conveyors, and others.
What factors affect a DC shunt motor?
The speed of a DC. Shunt motor is solely reliant on induced e.m.f. Flux and armature current are related.
What will occur if the DC shunt motor field is opened?
The armature current will again rise if the shunt field opens while there is no load. The engine would keep speeding up since relatively little torque is required to overcome the windage and friction.