Synchronous motor ppt

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V-Curves And Inverted V-Curves Of Synchronous Motor

Products Sold on our sister site CrystalGraphics. Title: Chapter 6 Synchronous Motors. Tags: armature chapter machine motors reaction synchronous. Latest Highest Rated. Besides, the current flow direction is reverse Since the current flow direction is reverse, the relation between the terminal and internal voltage is 6 No Transcript 7 The phasor diagram of a synchronous generator with lagging power factor load The induced torque is opposing the applied torque from prime mover 8 The phasor diagram of a synchronous motor The induced torque drives the motor rotation.

Thus, the pull-out torque is maximum induced torque. That is, d 90 degrees. When the load torque increases? The motor will slow down rotor mechanical speed The stator rotation flux still remain its constant speed stator flux speed Thus, the power angle d increases Finally, the synchronous motors will generate a large torque that is equal to the load torque.

However, if the maximum induced torque is still lower than the load torque? The power supply by the motor is Pm wtload The terminal voltage Vf supplies to the motor is constant 22 The phasor diagram increase the field current 23 What is the effect of increasing field current What is the meaning of the power factor of the motor changes from lagging to leading can support Q to the electrical system The motor is now acting like a capacitor-resistor combination load, and the magnitude of the capacitor can be changed by the field current 24 Synchronous motor V curve A plot of IA versus IF for a synchronous motor is the V curve.

Meanwhile, the harmonic content is also important reason 41 The synchronous capacitor or synchronous condenser A synchronous motor can be operated overexcited to supply reactive power Q for a power system. No real power have been drawn from the load and the shaft of the motor is removed 42 The V curve of the synchronous capacitor 43 Starting the synchronous motors How to start the synchronous motor?

What is the problem of the synchronous motor in starting? The speed of the stator magnetic field can then be increased gradually up to 60Hz Notably The stator voltage must also be reduced to prevent the over-current in stator winding. EA Kfw The power electronics can build the inverter to achieve the variable frequency and voltage drive 48 Motor starting by using damper windings The damper or amortisseur windings are special bars laid into notches carved in the face of a synchronous motors rotor, and then shorted out on each end by a large shorting ring.

Salient pole rotor and cylindrical rotor 61 Until now the result is The following result is only valid for cylindrical rotor The salient pole rotor has another reluctance torque 62 The effect of armature reaction in a salient-pole synchronous generator The rotor magnetic field and the induced voltage on the stator conductor 63 The effect of armature reaction in a salient-pole synchronous generator If a lagging load is connected to the terminals of this generator 64 The effect of armature reaction in a salient-pole synchronous generator The stator magnetic field is no more 90 degrees behind the armature current 65 No Transcript 66 The stator voltage Each component of the stator magnetic field produces a voltage in the stator winding by armature reaction.

The total voltage in the stator is thus 67 Now we may include the armature self- resistance and reactance The armature self-reactance is independent of the rotor angle 68 How to plot the phasor diagram?

The armature current IA is broken into Id and Iq by angle dq Usually, the torque angle d is unknown, and the power factor angle is q known. Without the knowledge of d, how to plot the phasor diagram? Once the angle d is known, the armature current IA can be broken into Id and Iq.

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That's all free as well!The reluctance motor is a type of synchronous machine. It has wound field coils of a DC motor for its stator windings and has no coils or magnets on its rotor. Unlike a conventional synchronous motor, both the rotor and stator of a switched reluctance motor have salient poles. A reluctance motor is a type of electric motor that induces nonpermanent magnetic poles on the ferromagnetic rotor.

Torque is. The number of phases is m and each phase is made up of concentrated coils placed on 2q stator poles. The rotor forms a magnetic circuit with the energized stator pole. The reluctance of a magnetic circuit is the magnetic equivalent to the resistance of an electric circuit. The reluctance of the magnetic circuit decreases as the rotor aligns with the stator pole.

When the rotor is inline with the stator the gap between the. When the rotor is aligned with the stator, the inductance will be very large and the slope decreases.

Apply a current to phase a with the current direction as shown in Fig. A flux is established through stator poles a and a and rotor poles r2 and r2 which tends to pull the rotor poles r2 and r2 towards the stator poles a and a, respectively. When they are aligned, the stator current of phase a is turned off and the corresponding situation is shown in Fig.

Now the stator winding b is excited, pulling r1 and. Likewise, energizing phase c winding results in the alignment of r2 and r2 with c and c, respectively. Accordingly, by switching the stator currents in such a sequence, the rotor is rotated. Similarly, the switching of current in the sequence of acb will result in the reversal of rotor rotation.

Since the movement of the rotor, hence the production of torque and power, involves a switching of currents into stator windings when there is a variation of reluctance, this variable speed motor is referred to as a switched reluctance motor SRM.

Working animation:.

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The initial classification is made on the basis of the nature of the motion i. If the magnetic field path is perpendicular to the shaft, which may also be seen as along the radius of the cylindrical stator and rotor, the SRM is classified as Radial field SRM.

Radial field SRMs is most commonly used. Radial field SRMs can be divided into shorter and longer flux paths based on how a phase coil is placed. The conventional one is the long flux path SRMs, in which the phase coil is placed in the diametrically opposite slots.

This type of SRMs is ideal for applications where the total length may be constrained, such as in a ceiling fan or in a propulsion application. These may be single-stack or. It is made up of four basic components: power converter, control logic circuit, position sensor and the switched reluctance motor. Machine construction is simple and low-cost because of the absence of rotor winding and permanent magnets. Bidirectional currents are not necessary, which facilitates the reduction of the number of power switches.

The torquespeed characteristics of the motor can be.A synchronous electric motor is an AC motor in which, at steady state[1] the rotation of the shaft is synchronized with the frequency of the supply current ; the rotation period is exactly equal to an integral number of AC cycles. Synchronous motors contain multiphase AC electromagnets on the stator of the motor that create a magnetic field which rotates in time with the oscillations of the line current.

The rotor with permanent magnets or electromagnets turns in step with the stator field at the same rate and as a result, provides the second synchronized rotating magnet field of any AC motor. A synchronous motor is termed doubly fed if it is supplied with independently excited multiphase AC electromagnets on both the rotor and stator.

The synchronous motor and induction motor are the most widely used types of AC motor. The difference between the two types is that the synchronous motor rotates at a rate locked to the line frequency since it does not rely on current induction to produce the rotor's magnetic field. By contrast, the induction motor requires slip : the rotor must rotate slightly slower than the AC alternations in order to induce current in the rotor winding.

Small synchronous motors are used in timing applications such as in synchronous clockstimers in appliances, tape recorders and precision servomechanisms in which the motor must operate at a precise speed; speed accuracy is that of the power line frequencywhich is carefully controlled in large interconnected grid systems. Synchronous motors are available in self-excited sub-fractional horsepower sizes [2] to high power industrial sizes.

These machines are commonly used in analog electric clocks, timers and other devices where correct time is required. In higher power industrial sizes, the synchronous motor provides two important functions. First, it is a highly efficient means of converting AC energy to work. Second, it can operate at leading or unity power factor and thereby provide power-factor correction.

Synchronous motors fall under the more general category of synchronous machines which also includes the synchronous generator. Generator action will be observed if the field poles are "driven ahead of the resultant air-gap flux by the forward motion of the prime mover ".

synchronous motor ppt

Motor action will be observed if the field poles are "dragged behind the resultant air-gap flux by the retarding torque of a shaft load ". There are two major types of synchronous motors depending on how the rotor is magnetized: non-excited and direct-current excited. In non-excited motors, the rotor is made of steel. At synchronous speed it rotates in step with the rotating magnetic field of the stator, so it has an almost-constant magnetic field through it.

The external stator field magnetizes the rotor, inducing the magnetic poles needed to turn it. The rotor is made of a high- retentivity steel such as cobalt steel. These are manufactured in permanent magnetreluctance and hysteresis designs: [4].

These have a rotor consisting of a solid steel casting with projecting salient toothed poles. Typically there are fewer rotor than stator poles to minimize torque ripple and to prevent the poles from all aligning simultaneously—a position that cannot generate torque.They are capable to achieve very high efficiency level and to gain the maximum efficiency class IE4 of IEC standard.

Both energy consumption as well as the environmental impact can be significantly reduced by adopting electric motors with high efficiency levels. Extended analysis of synchronous relactance machines, their control algorithms, related examples and experimental results can be found in [8] to [16].

The complex and anisotropic design of the rotor lamination generates different geometric reluctances in the d-axis and the q-axis and, if a magnetic field is applied to such anisotropic rotor, torque is produced as the rotor attempts to align the magnetically conducting direction to the stator field. In the SRM, the stator field is produced by a sinusoidally distributed winding in a slotted stator and it links the stator and rotor through a small air gap, exactly as in a traditional ACIM.

The field is rotating at synchronous speed and can be assumed to have a sinusoidal distribution. Basically the synchronous reluctance motor is a true AC rotating field machine, requiring a balanced polyphase sinusoidal supply into a distributed winding, which for all intents and purposes is identical to that of the induction machine of the same power rating.

The inherent advantages of SR motor technology over IM technology are:.

synchronous motor ppt

Just to focus on further considerations about power losses, in modern IMs with a short circuit rotor cage, the losses associated with the rotor amount to 20—35 percent of the total motor losses.

Synchronous rotation eliminates most of these associated losses. For a complete analysis, the characteristics that could be considered disadvantages are:. Thanks to such characteristics, the SynRM can be designed for the same frame size as an equivalent power IM, but achieving the latest IE4 efficiency standard rating.

You have to take into account that the majority of the losses in the synchronous reluctance machine are confined to the stator copper windings, where it is generally easier to remove heat than the rotor, which is a major challenge in the Induction Machines.

The SR motor has a rocky history in its development but has had a fraction of the attention and expenditure deserved to different motor technologies ACIM and PM in particular. SME S. SME has engineered and manufactured SR motors in a wide range of output powersuitable and available for applications in the industrial, material handling and automotive markets and will continue working on their improvement and enlarging their power range since such arising technology will be the next big jump ahead in the future for a wide range of electrical motor applications.

Your email address will not be published. Sign me up for the newsletter! SME Shanghai Co. Your Name required. Your Email required. Your Message. Just type and press 'enter'. Looking back to the history to jump ahead in the future.Facebook Twitter.

Similar to a d. If a three phase supply is given to the stator of a three-phase alternator, it can work as a motor.

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As it is driven at synchronous speedit is called Synchronous generator. So if alternator is run as a motor, it will rotate at a synchronous speed. Such a device which converts an electrical energy into a mechanical energy running at synchronous speed is called synchronous motor. The synchronous motor works only at synchronous speed and cannot work at a speed other than the synchronous speed. Its speed is constant irrespective of load, no doubt, its speed changes for an instant at the time of loading.

In this chapter, we will discuss how synchronous motor works and working principle of three-phase synchronous motor. Before beginning the study of the synchronous motor, it is necessary to study the production of the magnetic field. The rotating magnetic field RMF is very important to understand the working of a synchronous motor.

Similar to d. The synchronous motor construction is basically similar to rotating field type alternator. It consists of two parts :. This is excited by a three phase a.

Practically most of the synchronous motors use salient i. The field winding is excited by a separate d. When two unlike poles are brought near each other, if the magnets are strong, there exists a tremendous force of attraction between those two poles. In such condition, the two magnets are said to be magnetically locked. If now one of the two magnets is rotated, the other also rotates in the same direction with the same speed due to the force of attraction i. The principle is shown schematically in the below figure.Facebook Twitter.

So it is called Reluctance Motor.

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Here we will discuss construction and working principle of Reluctance Motor. The reluctance motor has basically two main parts called stator and rotor. The stampings are slotted on its periphery to carry the winding called stator winding.

synchronous motor ppt

The stator carries only one winding. This is excited by single-phase a. The laminated construction keeps iron losses to a minimum.

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The stampings are made up of material from silicon steel which minimises the hysteresis loss. The stator winding is wound for certain definite number of poles. The rotor has a particular shape. Due to its shape, the air gap between stator and rotor is not uniform. The rotor is free to rotate. The reluctance i. More the air gap, more is the reluctance and vice-versa. Due to the variable air gap between stator and rotor, when the rotor rotates, reluctance between stator and rotor also changes.

The stator and rotor are designed in such a manner that the variation of the inductance of the windings is sinusoidal with respect to the rotor position. Must Read: Principle and working of Synchronous generator or alternator. Construction of reluctance motor.

The stator consists of a Single Winding called main winding. But single winding cannot produce rotating magnetic field.

Construction & Working principle of Synchronous Motor

So for production of rotating magnetic field, there must be at least two windings separated by the certain phase angle. Hence stator consists of an additional winding called auxiliary winding which consists of a capacitor in series with it. Thus there exists a phase difference between the currents carried by the two windings and corresponding fluxes. Such two fluxes react to produce the rotating magnetic field. The technique is called split phase technique of production of the rotating magnetic field.

The speed of this field is the synchronous speed which is decided by the number of poles for which stator winding is wound. This textbook " Electrical Machinery by P. Bhimbhra " is the best in industry. Grab it now for very less price. The rotor carries the short-circuited copper or aluminium bars and it acts as a squirrel-cage rotor of an induction motor. If an iron piece is placed in a magnetic field, it aligns itself in a minimum reluctance position and gets locked magnetically.

Similarly, in the reluctance motorrotor tries to align itself with the axis of rotating magnetic field in a minimum reluctance position. But due to rotor inertia, it is not possible when the rotor is standstill. So rotor starts rotating near synchronous speed as a squirrel cage induction motor. When the rotor speed is about synchronous, stator magnetic field pulls rotor into synchronism i.

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Then rotor continues to rotate with a speed equal to synchronous speed. Such a torque exerted on the rotor is called the reluctance torque. Thus finally the reluctance motor runs as a synchronous motor. The resistance of the rotor must be very shall and the combined inertia of the rotor and the load should be small to run the motor as a synchronous motor.Synchronous motor and induction motor are the most widely used types of AC motor.

Construction of a synchronous motor is similar to an alternator AC generator. A same synchronous machine can be used as a synchronous motor or as an alternator. Synchronous motors are available in a wide range, generally rated between kW to 15MW with speeds ranging from to rpm. Construction of synchronous motor The construction of a synchronous motor with salient pole rotor is as shown in the figure at left. Just like any other motor, it consists of a stator and a rotor.

The stator core is constructed with thin silicon lamination and insulated by a surface coating, to minimize the eddy current and hysteresis losses.

The stator has axial slots inside, in which three phase stator winding is placed. The stator is wound with a three phase winding for a specific number of poles equal to the rotor poles. The rotor in synchronous motors is mostly of salient pole type. The direct current excites the rotor winding and creates electromagnetic poles.

synchronous motor ppt

In some cases permanent magnets can also be used. The figure above illustrates the construction of a synchronous motor very briefly. Working of synchronous motor The stator is wound for the similar number of poles as that of rotor, and fed with three phase AC supply. The 3 phase AC supply produces rotating magnetic field in stator. The rotor winding is fed with DC supply which magnetizes the rotor.

Consider a two pole synchronous machine as shown in figure below. Now, the stator poles are revolving with synchronous speed lets say clockwise.

Chapter 6 Synchronous Motors - PowerPoint PPT Presentation

If the rotor position is such that, N pole of the rotor is near the N pole of the stator as shown in first schematic of above figurethen the poles of the stator and rotor will repel each other, and the torque produced will be anticlockwise. The stator poles are rotating with synchronous speed, and they rotate around very fast and interchange their position. But at this very soon, rotor can not rotate with the same angle due to inertiaand the next position will be likely the second schematic in above figure.

In this case, poles of the stator will attract the poles of rotor, and the torque produced will be clockwise. Hence, the rotor will undergo to a rapidly reversing torque, and the motor will not start. But, if the rotor is rotated upto the synchronous speed of the stator by means of an external force in the direction of revolving field of the statorand the rotor field is excited near the synchronous speed, the poles of stator will keep attracting the opposite poles of the rotor as the rotor is also, now, rotating with it and the position of the poles will be similar throughout the cycle.

Now, the rotor will undergo unidirectional torque. The opposite poles of the stator and rotor will get locked with each other, and the rotor will rotate at the synchronous speed. Characteristic features of a synchronous motor Synchronous motor will run either at synchronous speed or will not run at all.

The only way to change its speed is to change its supply frequency. They need some external force to bring them near to the synchronous speed. They can operate under any power factor, lagging as well as leading.

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