According to the Faraday’s law of electromagnetic induction, emf gets induced in the rotor. When we apply a single phase AC supply to the stator winding, the magnetic field gets produced, and the motor rotates at speed slightly less than the synchronous speed Ns. The rotor is cylindrical and has slots all over its periphery. Synchronous speed Ns is given by It can also occur on account of causes within the motor itself like badly soldered winding connections or an ‘open’ within the winding. How to Identify starting and running winding in a single-phase motor If you open the single-phase motor, you will find out that your motor has two types of winding of which one is made from thick wire gauge and one thin. Each of these components will rotate in the opposite direction, with the synchronous speed, Ns. Three phase induction motor (self starting in nature) Single phase induction motor (not self starting) Other Squirrel-cage induction motor Slip ring induction motor 18. Current will flow through two phases only. Also, both of these components of flux are equal in magnitude. In the case of a ‘delta/star’ transformer, the heavily loaded line carries, twice the normal current. The stator of the single-phase induction motor has laminated stamping to reduce eddy current losses on its periphery. Permanent split capacitor motor or single value capacitor motor. (ii) Capacitor motors-started by two-phase motor action through the use of an auxiliary winding and a capacitor. For example, Zhou has used this method to study three-phase and single-phase induction motors [4]. We use the single-phase power system more widely than three phase system for domestic purposes, commercial purposes and some extent in industrial uses. ThreeIV. From the above topic, we can easily conclude that the single-phase induction motors are not self-starting because the produced stator flux is alternating in nature and at the starting, the two components of this flux cancel each other and hence there is no net torque. Faraday’s law of electromagnetic induction, SCADA System: What is it? Let us call these two components of flux as forwarding component of flux, φf and the backward component of flux, φb. 2. NPTEL provides E-learning through online Web and Video courses various streams. SSC JE 3-Phase Induction Motor Solved Question (2018-2009) Ques.1. Except for shaded pole motor, the asynchronous motor has two stator windings namely the main winding and the auxiliary winding. In the range of 40 – 60% load, protection by overload relays will be provided if their setting corresponds to the load on the motor. The single phase motors are simple in construction, cheap in cost, reliable and easy to repair and maintain. -phase Induction Machines Dr. Suad Ibrahim Shahl 14 Example 1: A 480V, 60 Hz, 6-pole, three-phase, delta-connected induction motor has the following parameters:τ ω) then the airgap power is positive. As its name indicates stator is a stationary part of induction motor. Now for producing this rotating magnetic field, we require two alternating flux, having some phase difference angle between them. Single phase synchronous motors. Induction Motor Problems - Solutions Q #1 A 2-pole, 3-phase induction motor, fed by a 60 Hz source, The Equivalent circuit of a Single Phase Induction Motor can be obtained by two methods named as the Double Revolving Field Theory and Cross Field Theory. If single-phasing occurs when the motor is not working, the motor will fail to start. The difference between the stator synchronous speed and rotor speed is called (SSC-2018 Set-1) Leading speed Lagging speed Slip Speed Slow But in case of a single phase induction motor, the stator has two windings instead of one three-phase winding in three phase induction motor. a loose or poor connection in the switch or starter. Consequence of that, motor protection is an emerging area of research. per phase (iii) the rotor reactance per phase at full load (iv) the rotor current and full load power factor. Current drawn by it under this condition will be 87% of the starting current under the normal condition. NOTE: We know that for the working of any electrical motor whether its AC or DC motor, we require two fluxes as the interaction of these two fluxes produced the required torque. •The starting of the motor requires the generation of a rotating magnetic flux similar to the rotating flux in a three-phase motor. Brauer and his colleagues also used a similar … Before jumping into the equivalent circuit, a few concepts are useful. Home >> Category >> Electrical Engineering (MCQ) questions and answers >> 3 - Phase Induction Motors 1) The frequency of the induced emf in an induction motor is a. P = No. Required fields are marked *. Like any other electrical motor asynchronous motor also have two main parts namely rotor and stator. • The starting of the motor requires the generation of a rotating magnetic flux similar to the rotating flux in a three-phase motor. 3-Phase induction machine construction • 3 stator windings (uniformly distributed as in a synchronous generator) • Two types of rotor: –Squirrel cageThe rotating magnetic field • The basic idea of an electric motor is to generate two Electrical4U is dedicated to the teaching and sharing of all things related to electrical and electronics engineering. Each of these components rotates in the opposite direction i. e if one φm/2 is rotating in a clockwise direction then the other φm / 2 rotates in an anticlockwise direction. If the motor is delta connected, current distribution will be as shown in Figure. less noisy). For loads above 60% of the rated load, the rise in the line current is such that the overload relay can take notice of the over-current even if the relay is set for 100% current. This main flux also links with the rotor conductors and hence cut the rotor conductors. In case of single phase induction motors, the stator winding produces an alternating magnetic field having maximum magnitude of Φ 1m. The use of re-wirable type fuses is not recommended for motor circuits because of their unreliable operation. 34.5 (a) 34.5. The motor will continue to run under the influence of the main flux only. Performance estimation was performed by considering the effect of core saturation, supply f = supply voltage frequency, View Homework Help - Induction Motor Solutions.pdf from EE 4701 at University of Minnesota, Morris. Since this flux is produced due to the induction principle so, the motor working on this principle got its name as an induction motor. To provide mechanical strength, these rotor conductors are braced to the end ring and hence form a complete closed circuit resembling a cage and hence got its name as squirrel cage induction motor. Induction Motor 1247 Fig. In actual practice, the current distribution may be somewhat different in some cases. Where motors above 15 KW may have to work for long periods on part loads of 40 – 60%, additional protection by single-phase preventers, which trip the starter on any serious imbalance in the currents of three-phases will be necessary. This rotor current produces its flux called rotor flux. We use cookies to ensure that we give you the best experience on our website. These two windings are placed in space quadrature to each other. Single-phase induction motor with embedded stator coils Single-phase induction motors may have coils embedded into the stator for larger size motors. The rotor in the single-phase induction motor is of squirrel cage rotor type. Single phase induction motors sizes vary from 1/400 kw to 1/25 kw are used in toys, hair dryers, vending machines etc. According to double field revolving theory, we can resolve any alternating quantity into two components. The rotor is wound for as many poles as the . Firstly, the single-phase induction motors are mostly provided with concentric coils. This current is called the rotor current. Single-Phase Induction Motor – Construction, Operation & Types of 1-Phase Induction Motors The single-phase motors are more preferred over a three-phase induction motor for domestic, commercial applications. If you continue to use this site we will assume that you are happy with it. The starting torque is also low for asynchronous motors/single phase induction motor. Single phase induction motors are simple, robust, reliable and cheaper for small ratings. The motor then operates as a single-phase induction motor and continues to accelerate till it reaches the normal speed. Full disclaimer here. Single-phase induction motors are the simple motors which operate on single -phase A.C. and in which torque is produced due to induction of electricity caused by the alternating magnetic fields. The single phasing of induction motor can occur because of causes external to the motor which are. In the case of a ‘delta/delta’ or ‘star/star’ transformer, the effect of blowing of a fuse on the primary side is the same as the opening of the secondary circuit. For example – a flux, φ can be resolved into two components No Load Test & Blocked Rotor Test of 3 phase induction motors - Duration: 15:03. i.e. These relays provide adequate protection to motors if the setting of relays is related to the load conditions because in that case, the relays can sense the overload and isolate the motor before any damage to the insulation can occur as a result of overheating. Current distribution during single-phase operation, if the motor continues to deliver the same power, will be as below: If the motor is star connected, line and phase current will be √3 I, where ‘I’ is the current under 3-phase balanced operation. If the capacitor of a single-phase motor is short circuited (a) the motor will not start (b) the motor will run (c) the motor will run in reverse direction (d) the motor will run in … Current will flow through two phases only. Greater than the supply frequency b. Single phase induction motors are of different types based … The squirrel cage rotor consists of aluminum, brass or copper bars. Current distribution during single-phase operation, if the motor continues to deliver the same power, will be as below:   If the motor is star connected, line and phase current will be √3I, where ‘I’ is the current under 3-phase balanced operation. In other cases, protection by thermal relays is more than adequate. the powe r is This alternating current produces an alternating flux called main flux. Single Phasing is the most common problem found in three phase induction motor. The equivalent circuit of any machine shows the various parameter of the machine such as its Ohmic losses and also other losses. Soln: (i) Ns = 120f/p = 120 x 50 /4 = 1500 rpm; slip = (Ns – N) / Ns = (1500 – 1460)/ 1500 = 0.0266 Percentage slip = 2 Three-Phase Induction Motor: Construction, Operation & Types of 3-Phase Induction Motors. The efficiency of single phase induction motors is less compared to that of three phase induction motors. The construction of single phase induction motor is almost similar to the squirrel cage three-phase induction motor. The single phase AC motors are further classified as: Single phase induction motors or asynchronous motors. The slots are provided on its stamping to carry stator or main winding. So, the single phase induction motors are not self-starting motors. We can easily adjust the number of turns per coil can with the help of concentric coils. This resultant flux is rotating in nature and rotates in space in one particular direction only. Now there are two fluxes one is main flux, and another is called rotor flux. A capacitor-start single phase induction motor is switched on to supply with its capacitor replaced by an inductor of equivalent reactance value. two-speed, condenser, single-phase axial flux induction motor with adjustable air gap is introduced (Nasiri-Ghedari and Lesani, 2013b). Though, the smaller sizes use less complex to build concentrated windings with salient poles. Hence the net torque experienced by the motor then operates as a induction. B. three-phase induction motor is switched on to supply with its capacitor replaced by an inductor of reactance... The mechanical load through the use of re-wirable type fuses is not recommended for motor circuits because causes. Sharing of all things related to electrical and electronics engineering produces its called. ( ii ) capacitor motors-started by two phase motor action through the use of re-wirable type fuses is not,! Distributed winding consisting of coils as used in toys, hair dryers vending... 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And cheaper for small ratings circuits because of their unreliable Operation kitchen equipment ensure that we give the! In portable tools, vacuum cleaners & kitchen equipment s law of electromagnetic induction, SCADA system What! Parameter of the starting torque is also low for asynchronous motors/single phase induction motors any instant time. Motors or asynchronous motors re-wirable type fuses is not recommended for motor circuits because of causes to. The backward component of flux are equal in magnitude resistance is taken into account provided on its to...

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