2) Maintain Proper Supply Voltage By Using Autotransformer Or Transformer Tap Changer. The most common use of three-phase power is for motors. These may be due to internal or external effects. 4. The table below gives the commonly encountered problems in 3 phase squirrel cage induction motors, cause of problems and what remedy to apply to bring the motor back to production. Rotor mass unbalance - this leads to air gap eccentricity. Mar 4, 2013 #6 … The prospective short-circuit current of a predictable fault can be calculated for most situations. Phase failure is a very common electrical fault experienced by three-phase motors. The various faults are: Mechanical faults: 1. An open-circuit fault occurs if a circuit is interrupted by some failure. Any value greater than 0.5 ohm indicates a motor problem. Motor current signal analysis (MCSA) is used in identification of artificially induced mechanical faults, and it is also supported with vibration signal analysis. Common motor failure and faults are: Overheating The most common mechanical faults are shaft imbalance, looseness, misalignment, and bearings. Air gap eccentricity . Further problems may need to be solved. In three-phase systems, a fault may involve one or more phases and ground, or may occur only between phases. In such case, motor may continue to rotate, but the two … Stator faults typically have a significant share amongst the common type of faults in industrial three-phase induction (asynchronous) motors. Arms. This fault is categorised as a mechanical fault. On a three-phase motor, the three resistance measurements should be nearly identical. The most common mechanical problems; mechanical unbalance, shaft misalignment, and bearing failures are investigated experimentally. Causes. 3) Reduced The Motor … It is evident from the chart that the highest contributor for failure in a three-phase induction motor is the bearing fault. and Rotor Winding Faults in Three-Phase Induction Machines. F. FrankUK. Single & 3PH motors will react to a restriction in movement by struggling to reach their optimum speed. Data collected from a 1/3 hp, 208 V three-phase squirrel cage induction motor is used in this project. A three phase induction motor is a type of AC induction motors which operates on three phase supply as compared to the single phase induction motor where single phase supply is needed to operate it. Differential protection is often provided for medium and large size motors with supply voltages of greater than about 4 kV, and electrically operated (shunt trip) circuit breakers. Loose cables. It is a type of polyphase system and is the most common method used by electrical grids worldwide to transfer power. Reactions: 5 people. Major F'rofessor: Chee-Mun Ong. The most common fault, the open-phase fault, is studied in this section. Vibration. Submerged Motor. The common failures of three-phase motor are described, the specific reasons of failure are analyzed, the treatment of common failures are illustrated, the motor repair methods are summarized, the troubleshooting process is pointed out, the developing direction of common troubleshooting is put forward. The symmetrical fault is sub-categorized into line-to-line-to-line fault and three-phase line-to-ground-fault. Figure 11 – A delta-connected motor that failed because of a single-phase condition, Line 3 is open. The connections are shown in Fig. The three phase fault clear of earth and three phase fault to earth are balanced or symmetrical short circuit faults while other remaining faults are unsymmetrical faults. 2. Richard Burns-Mentor. Three-phase motors must be connected to a nominal voltage to function properly. It provides a unique feature which is a rotating field in order to rotate the motor without the need of a starter circuit. If for any reason any of the phases that supply the motor are disconnected, the motor continues to operate … Three-phase electric power is a common method of alternating current electric power generation, transmission, and distribution. 6. markythesparky-Arms. Motor Operation. Three Phase Faults. 3 PHASE INDUCTION MOTOR FAULT LIST AND SOLUTION Problems: Like Causes: What To Do: 1) Motors Fails To Start/Accelerate 1) Connection Of Motor Is Not Proper. Often these mechanical faults are related: shaft imbalance, looseness, or misalignment left uncorrected will cause increased forces on the bearings … If all three reading are exactly the same, there would be a 0 percent resistive imbalance. Motor failures come in three basic types: electrical, mechanical and mechanical that progresses into electrical. This paper presents a motor current signature analysis (MCSA)-based diagnostics of the stator winding short circuit fault. To find the fault current at any point in the network, a sum is made of the impedances in the network between the source of supply (including the source impedance) and the point at which the fault … 2) Supply Voltage Is Low (Less Than 415 Volt In Any Of 3 Phases). Radial Bases The three phase supply current produces an electromagnetic field in the stator winding which leads to generate the torque in the rotor winding of three phase induction motor having magnetic field. faults in three phased induction motors. In simple terms, the current is being alternated during a different time. If a three-phase motor has been submerged in water but not energized, there’s a good chance it won’t need rewinding or replacing. The generator neutral is earthed through an impedance. Reaction score 235. An unloaded star-connected 3-phase alternator is shorted by a 3-phase fault. The ability of a multiphase machine managing the fault operation lies in the greater number of phases and in the greater number of independent variables that model the system. Common practice is Zs to the starter or isolator, then R1+R2 to the motor. Modern electric motors may be more efficient and reliable than their ancestors, but they can still fail sometimes. This type of fault happens due to the destruction of the turn insulation, and can be very detrimental causing motor shutdown. As one or more phases develop a high resistance the resistive imbalance increases, indicating a fault. The L – L – L fault occurs rarely, but it is the most severe type of fault which involves the largest current. This paper presents a motor current signature analysis (MCSA)-based diagnostics of the stator winding short circuit fault. Broken rotor bar- this leads to mechanical stress and thermal stress. 5. 22 March, 2018 by Sistemas Trespuntos Industrial, International 0 comments. Cleaning and baking the windings may be all that’s needed. Induction motor fault finding 03/10/2010 by Lemau 11 Comments Induction motor is common application for domestic and industrial for machinery and production equipment.We can found electric motor in every where and should have a basic knowledge about how to troubleshooting or fault finding when we facing the motor breakdown. Introduction It is well understood that squirrel-cage induction motors are rugged, reliable, cheap, and thus widely used in industrial and manufacturing processes. a. Go back to Contents Table ↑ 6. Single Phasing is the most common problem found in three phase induction motor. Stator faults typically have a significant share amongst the common type of faults in industrial three-phase induction (asynchronous) motors. Loose … 3. Three-Phase Squirrel-Cage Induction Motors Ying Xie Harbin University of Science and Technology, China 1. Esteemed. A Phase Imbalance Fault indication on a motor monitor means that the voltage and / or current in one phase winding of the motor is not the same as the other two phases by an amount that exceeds a settable maximum. Line – Line – Line Fault – Such types of faults are balanced, i.e., the system remains symmetrical even after the fault. The purpose of this work is to investigate the efficiency of existing methods for on-line fault detection when applied to three-phase induction motors, spc:cifically to test known theoretical calculations of harmonics developed by certain types of faults experimentally. Another common fault stems from mechanical rubs, which can be the result of looseness of the motor shaft and/or the motor bearings. In restricted earth fault scheme the common terminals of phase CT are connected to the secondary of Neutral CT in such a manner that secondary unbalance current of phase CT and the secondary current of Neutral CT will oppose each other. Power supply test: For three-phase motors, the expected voltage between each of the three-phase supply lines for the 230/400 V system is neutral from 230V and 400 V. Check that the multimeter is used to apply the correct voltage to the motor. How long do electric motors actually last before they break down? 2. This paper presents an artificial neural network (ANN) based technique to identify faults in a three-phase induction motor. 3) Motor Is Overloaded. The differential protection provides high speed direction and clearance of faults on the motor stator windings. The most common reason for this fault to appear is from loss of a single phase in the supply to the motor. This is accomplished due to the fact that each one of the three phases has a different offset. The objectives of this study are to develop a SVM based induction motor external faults identifier and study its performance with real-time induction motor faults data. To protect the motor from different faults conditions various protections are provided. Bearings Overheating and lack of Pressure of Lubrication Oil. Single Phasing Condition: when one of the supply fuse of a three-phase motor blows off or a terminal connection comes out, single phasing at the motor may occur. Distribution of faults in induction motor The factors responsible for failure of three-phase induction motor are highlighted in (Fig.2). Martin McGuffie explains three common causes of electric motor failure: weakened insulation, contamination and lack of maintenance. This will require more power when a restriction is in place & thus create an overload situation. In a "ground fault" or "earth fault", current flows into the earth. 5.1. Mar 4, 2013 #5 An earth fault loop impedance test is performed on a circuit before a piece of equipment, not in the equipment itself. 7. Electrical faults: 1. 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