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Single Phasing in Polyphase Electrical Motors

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Single Phasing in Electrical Motors In a polyphase machine when one phase gets disconnected from the machine, this condition is known as single phasing. In an induction motor, single phasing causes the motor to slow down and increased amount of current flows in the winding of the 2 phases of the motor which may cause the motor windings to burn and eventually the motor will be disconnected from the supply. Effect of Single Phasing The following are the effects of single phasing: 1) Due to single phasing the current in the remaining two phases increases. 2) Single Phasing reduces the speed of the motor. 3) The motor becomes noisy and starts vibrating due to uneven torque produced in the motor. 4) If the motor is arranged for standby and automatic starting then the motor will not start, and if the overload relay provided fails to function then the motor may burn. 5) The windings will melt due to overheating and can give a fatal shock to the personnel. 6) It m
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HIGH TORQUE CAGE MOTORS

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HIGH TORQUE CAGE MOTORS The rotor of of an induction motor can be designed in two types : a: Squirrel cage rotor b: Slip ring rotor For both of them the stator part connection is same, no change. At squirrel cage rotor we can not add external resistance which means speed and torque cannot be controlled. But in slip ring type of rotor we are able to add external resistance and we have a full control over the speed and torque of induction motor. So deep bar and double rotor is only applicable in squirrel cage induction motors. The starting torque of a squirrel cage induction motor is only 1.5 times of full load torque, and the current drawn is very hight it's 5 to 7 times of full load current, this is because the rotor resistance is very low. So deep bar and double cage rotor are used to provide more rotor resistance and to decrease the current. The motive is to provide efficient starting torque and effective starting current drawn. 1. Deep Bar Cage Motor
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Thermal Power Plant part-1

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Thermal power plant   Thermal power plant converts the chemical energy of the fossil fuel into electrical energy Thermal :- Thermal is a movement of rising warm air. It is taken from Greek word 'Therme'  which means heat. In thermal power plant we derive heat by burning coal so we refer it as a thermal power plant. Why thermal power plant is also called as steam power plant ? Because in this power plant we use steam of water of high pressure to drive the steam turbine which rotates the alternator. Alternator is also known as synchronous generator which is used in thermal power plant due to its synchronous speed that is constant speed at varying input. Sometimes thermal power plant is also referred as coal power plant, why ? Because in this Thermal power plant we use coal as a fuel to convert water into steam and hence we refer it as coal power plant also. Site selection of a thermal power plant Availability of raw material   Nature of land   Cost of land 
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Location: Unnamed Road, Kamta, Lucknow, Uttar Pradesh 226028, India
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Salient Pole Rotor Vs. Non-Salient or cylindrical Pole Rotor

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Salient Pole Rotor Vs. Non-Salient Pole Rotor In salient pole type of rotor consist of large number of projected poles (salient poles) mounted on a magnetic wheel. Construction of a salient pole rotor is as shown in the figure at left. The projected poles are made up from laminations of steel. The rotor winding is provided on these poles and it is supported by pole shoes. Salient pole rotors have large diameter and shorter axial length. They are generally used in lower speed electrical machines, say 100 RPM to 1500 RPM. As the rotor speed is lower, more number of poles are required to attain the required frequency. (Ns = 120f / P   therefore, f = Ns*p/120   i.e. frequency is proportional to number of poles). Typically number of salient poles is between 4 to 60. Flux distribution is relatively poor than non-salient pole rotor, hence the generated emf waveform is not as good as cylindrical rotor. Salient pole rotors generally need damper windings to preven
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Slip Ring vs Squirrel Cage Induction Motor

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Slip Ring & Squirrel Cage Induction Motor The squirrel cage induction motor is the most popular type of AC motor. It is very commonly used in industries because it is very cheap, robust, efficient, and reliable. The slip ring motor has very little application in industries. Rarely 5% – 10% slip ring motors are used in industries because it has several disadvantages like it required frequent maintenance, having a high copper loss, etc. One of the major difference between the slip ring and the squirrel cage motor is that the slip ring motor has an external resistance circuit for controlling the speed of the motor. Whereas in squirrel cage motor, it is not possible to add any external circuit because the bar of the motor is permanently shorted at the end of the ring. Some other differences between them are explained below in the comparison chart. Key Differences Between Slip Ring & Squirrel Cage Induction Motor The motor whose rotor is wound type such type
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DIFFERENT TYPES OF ELECTRICAL MOTORS AND THEIR APPLICATIONS

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DIFFERENT TYPES OF ELECTRICAL MOTORS AND THEIR APPLICATIONS all modern industrial and commercial undertakings employ electric drive in preference to mechanical drive because it possesses the following advantages : It is simple in construction and has less maintenance cost.  speed control is easy and smooth It is neat, clean and free from any smoke or flue gases. It can be installed at any desired convenient place thus affording more flexibility in the layout. It can be remotely controlled. Being compact, it requires less space. It can be started immediately without any loss of time. It has comparatively longer life. 1. DC Series Motor Since it has high starting torque and variable speed, it is used for heavy duty applications such as electric locomotives, steel rolling mills, hoists, lifts and cranes. 2. DC Shunt Motor It has medium starting torque and a nearly constant speed. DC shunt motor is used for driving constant speed line shafts, lathes, vacuum cleaners, wood
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Location: 101 Sheng Dao, Tiane Xian, Hechi Shi, Guangxi Zhuangzuzizhiqu, China
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Effect of Harmonics on Performance of 3-phase Induction Motor

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Effect of Harmonics on Performance of 3-phase Induction Motor The induction motor performance is affected by the harmonics in the time variation of the impressed voltage. But its effect on the performance of the motor is not predominant hence it is not considered here. The torque-slip characteristics as shown in Fig is obtained when the space distribution of flux wave along the air gap periphery is sinusoidal. But the air gap flux is not purely sinusoidal as it contains odd harmonics (5 th , 7 th , 11 th  etc). Hence at low speeds, the torque-slip characteristic is not smooth. The distribution of stator winding and variation of air gap reluctance due to stator and rotor slots are main causes of air gap flux harmonics.        The harmonics caused due to variation of air gap reluctance are called tooth or slot harmonics . Due to these harmonics produced in air gap flux, unwanted torque are developed along with vibration and noise. Each space harmonic can be considered
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