Catalog
Ⅰ What are AC motors?
AC motor, powered by alternating power, is a popular form of electric motor. AC motors provide a comparatively powerful method of extracting mechanical energy from a mere input signal, just as many efficient practical motors used in daily industrial applications (as well as hobby ventures, domestic commodities, and other professional devices and consumer products).
AC motors are differentiated by several key criteria from many other electric motor types - particularly somewhat more familiar DC motors (direct current). The most important of these is the fact that an AC motor directly relies on the alternative current flow across its circuit to achieve mechanical energy efficiency. In the following parts of this guide, we will explore this particular method a little more thoroughly.
AC motor
AC motors also differ from DC motors because most AC motors do not consist of brushes. This also ensures that the need for maintenance and replacement of parts on the AC motor is significantly reduced and as a result, most consumers usually expect a longer average life expectancy. As opposed to DC motors the speed of the AC motors for several different models is usually determined by a frequency drive control - once again, in this guide, we will briefly outline a number of possible changes to the basic AC motor model.
Due to their reliability, low production costs, general affordability, and operational ease, a variety of AC motors are often used in a diverse catalog of well-known consumer goods and industrial equipment.
Ⅱ AC motors working principle
As already mentioned, the main characteristic that distinguishes AC motors from numerous other motor types - mostly DC motors – is that they operate on alternating currents in particular. There are other variations too, but this is crucial to understanding how AC motors function precisely.
An alternating current or load - usually shortened to AC, thus an AC motor - has a flux path that flows regularly around a circuit. (The current direction switching feature often means a regular shift in the voltage on an AC circuit.) In comparison, only one way around a circuit runs a DC or direct current and hence volume stays reasonably consistent on a DC circuit.
AC motor internal structure
In order to generate this alternative charge path, the AC currents and AC motors by extension depend on a system called an alternative. An alternator is a type of electric generator that usually produces an electromagnetic field (EMF) when electricity is transported by a rotating shaft (the rotor) that turns around or within a number of static wire spools (the stator). As the rotor turns in relation to the stator, the resulting EMF changes the direction or polarity.
Due to the polarity at set points relative to statisor, an EMF generated by a charged rotor turning on a fixed axis will cause the current direction to reverse regularly and at predictable intervals in an AC motor. The alternator and current on the AC circuit usually work as if it were a piston or a paddle of water flowing through a pipe system – when the piston goes in and out, it then pushes through it.
Another major difference between AC and DC motors, as stated previously, is that AC motors have no brushes. In a traditional DC motor, the brushes are the electricity that leads directly from the power-producing part to the armature, which is why a DC motor is often referred to as a conductive motor.
In contrast, some brushless AC motors are also provided as examples for an induction motor, as electromagnetic induction is known as an alternate charge from an EMF through a rotor and stator.
Ⅲ Different types of AC motors
In today's market, there are various AC motor models, each with slightly different operating characteristics and power outputs.
Irrespective of the many peripheral data and specifics that may be covered by the manufacturer's instructions, the main difference between most specific models of the AC motors is how their rotors are built, as this often determines their range of functional skills.
The best option for each mission, like all such electric components, depends on the application's specifics and the position you need the AC motor to fulfill. In the following parts, we describe some of the most common classes and subtypes which you will probably meet when you purchase online AC motors.
1.Induction motors
As described above, an induction motor is a certain type of AC induction motor that uses an electrically locked spinning rotor to create an EMF around a stator and thus generate the critical alternating current that can then be converted from the AC motor into mechanical energy.
AC induction This kind of motor is often known as asynchronous motors since, as a general rule, the output rotor is slower than the frequency it receives elsewhere. This means that the motor rotates 'out of sync' with the supply of fuel.
This is important because the charging produced by electromagnetic induction, which is the only source of electrical "excitement" the frame receives, is another key feature of a true induction motor. If the rotor is turned precisely at the same speed as the magnetic field rotating on the stator, there would be no current induced and a more energy source would be required for the frame. This is done with a DC induction motor, which directly drives the current into the frame or a synchronous AC induction motor (see below).
2.Synchronous motors
A synchronous AC motor is a special kind, in which the output speed of the rotor is matched directly with the rate of alternating current. Whereas no current is normally induced by an AC induction or asynchronous induction motore structure, usually the synchronous AC motor has additional components, known as the slip ring, which allow current transmission from rotating to fixed components of the motor.
Slip rings are electromechanical devices that enable the transmission of electrical signals from power-generating components by electromechanical systems. With the synchronous AC motor, the rings produce the magnetic field required around the rotor to enable it to rotate at the same rate as the supplied alternating current without breaking the current flow.
To sum up, AC synchronous motors are named because the rotor speed is directly proportional to the Stator's spinning magnetic field. They seem to be a favorite choice where greater precision, for example in clocks and other schedule devices, is a significant factor in the application.
3.Squirrel cage motors
Instead of a series of wound bobbins, the Squirrel cage motors are an asynchronous AC induction motor that uses cage rotors - a simple robust design with a solid-metal roller used for the conduction of current through the rotor.
As there is no moving rotor contact inside the rotor system itself in the conductive rotor bars (these are permanently short-circuited by integrating them into end rings), the squirrel cage motors are regarded as the more stable, heavier maintenance alternative and are significantly cheaper to manufacture and purchase than the wound or ring rotor slip.
The downside is that the squirrel cage can't be connected to a circuit in series by the permanent short-circuit construction, i.e. you can't regulate the current caused in the rotor winding outside the current. In practical terms, this usually means a high starting torque is needed and the initial torque is very low up to full speed.
However, additional components such as variable speed drives (VSD) and low-voltage starters can to some degree alleviate these deficiencies. In applications where a low starting torque and lack of speed control do not present a major problem, such as pumps and air compressors, squirrel cage induction motors are often used.
4.Shaded pole motors
Shaded-polar AC motors are a subtype of a single Phase squirrel cage engine identified by the use of a copper or bar auxiliary rotor winding, known as a shading coil.
They are suitable for multiple speeds, unlike regular squirrel cage motors, but they produce a relativ small starting torque compared to their full-speed torque. Shaded-pole motors usually are economic to produce and affordable to purchase, but due to their simple robust construction they are remarkably reliable.
For all these reasons, shaded-pole motors are also a leading option for AC motor assemblies for power supply arrays and other fractional power supplies with easy start-up loads, such as:
Record players
Toys
Electric clocks
Hairdryers
Other small instruments
Ⅳ Differences to DC Motors
Historically, industrial DC motors were of the type of brush. Comparing AC motors, DC motors with brushes and commutators have some inconveniences: additional maintenance (brush replacement), narrow speed ranges, and a shorter overall life span. AC induction motors have no brushes and a long lifetime.
The DC motor speed is regulated with different armature current while the AC motor speed is controlled with a different frequency, often a variable frequency drive DC motor rate (VFD).
In recent decades, brushless DC motors have come out, largely as a result of the invention of the required semiconductor control system and the availability of high-quality permanent magnets. No brosses, no physical switch, and thus an increased service life of the brushless DC motors are required. The pace constraints of brushed models are also overcome.