DESIGN AND MODELING OF DUAL CAGE ROTOR INDUCTION MOTOR (DCRIM) Ekum, A. Eyam1, Akisot, E. Etetim.2 and Akpama, E.J3 123 Department of Elect/Elect Engineering-Cross River University of Technology, Calabar/Nigeria ekumawunaeyam079@gmail.com, akisote@yahoo.com and ekoakpama2004@yahoo.com Abstract Modeling Engineering systems is becoming more interesting following the development of modeling software. Modeling with/without assumptions proves helps to validate results and reduce waste of time and resources during construction. It is on this premise that, the idea of induction machine circuit design and modeling is conceived. For sustainable engineering design and fabrication, modeling and simulation of systems become imperative. The aim of this paper therefore, is to look at the development and expected test outcomes of dual fixed rotor induction machine (DCRIM). Among different strategies, the limited components method is utilized to carry it out. The distinctive reference frames are to be utilized to dissect the presentation of the machine at different rated speeds and the comparing speed – torque qualities under its consistent (Steady) state. Models, for example, dq0 model, electrical model and the mechanical model are to be utilized. At the rated power of 15KW is the circuit modeled. Boundaries will be determined and chosen from an ideal standard induction motor with poles pairs of 2p=4. Maxwell 2D and RMxprt instruments are utilized for the simulation. The simulation result of the ordinary induction motor model and that of the double cage rotor model was compared, and these show that there is consistency between the introduced model and the selected motor parameters with respect to the results findings in the operating torque rose from 0-1860N-m and fell uniformly over the range to 1680N-m, the phase current maintained stability in rising and the dropping completely; the output power performance increased uniformly from 1KW to 15KW all through the motor running process, the RMxprt current windings decreased from 12.7A to 6.7A during the process and across phase A, B and C. Simulating induction motors especially the double cage rotor type of motor is more precise with the use of the Ansys (Analysis System) Maxwell two dimensional (2-D) and RMxprt tools due to their electromagnetic influence. Keywords: Dual cage, RMxprt, Maxwell 2-D, Induction motor, induction modeling Introduction Every industry thrives at its best affordable technology with low cost and easy maintenance but with the current failures or limitations of the ordinary (simple) induction motors in our industries, hence, the urgent need for its replacement with the double caged rotor induction motor (DCRIM) [13][17]. Thus, waste of time, money and other resources are avoided or drastically reduced while constant production and availability of machinery is actualized [17][20]. As the demand for more production is on the daily growth, hence the need for more reliable and efficient machining process [9]. Considering the Induction Machine (IM) as a very common but robust machine used in our industries, though it is very rugged and strong, hence, other circumstances like rotor breakage and flux leakage have made it most time to become inefficient, hence production and other forms of output are affected. [1] Trying to fix this problem commonly faced by the single rotor induction motor has resulted to the design and used of the Doubled caged Rotor Induction Motor (DCRIM), [2][4][12]. The design of this motor is to solve the problem or limitations inherent with the single Induction Motor (IM)[19]. The Maxwell two dimensional (2-D) and RMxprt tools are used to run this simulation [17]. The results are presented in plots. Computer modeling tools are very useful in simulation cases as this [12][17][20]. Table 1. ComputerSpecifications for simulation The computer platform or space Windows Ram Processor 8.0 Pro 2.00 GB Intel core i4 InsideTM 64 Bit operating system 1600 MHz Table 2:Mesh Elements of the Simulated Motor Standard motor used Double cage rotor motor simulated Meshed elements of the motor 47352 Simulation time in h/m/s 02:15:22 6256 04:07:11 While the second table shows the pattern with which the elements are being meshed together. The figure 1 shows an RMxprt interface indicating the stator windings of a two fold (dual rotor) induction motor with the three phase coils not being connected. Figure 1: RMxprt modeler with unconnected phase coils From figure 1, the total number of slots selected for the simulation is 36 and the modeled and simulated slots is shown in the figure 2 with its specifications. From the figure 2, the following parameters with all dimensions in millimeters (mm) represents the modeled slot. Hs0 = 2mm Bs1= 5mm Hs1 =0mm Figure 2: Modeled slot Bs0 = 1.5mm Bs2 =5mm Hs2 = 0mm Figure 3: RMxprt modeler with connected phase coils From the figure 3, the three phase A, B and C are connected systematically as described in the nested part of figure 3. Each connection showing the turns and the slots in outer and inner position. This is done to achieve flux linkages among the three phase of the motor. 2.0 Induction motor design model in Ansys and RMxprt The tools frequently used at commercial value by simulation field engineers for the electromagnetic designing and analyzing 2-D and 3-D for transformers, motors, coils, actuators etc is the Ansys (Analysis System) Maxwell software [7][17][19][20]. RMxprt is another commercial tool developed by ANSYS which is embedded with the capacity to design and simulate electrical machines. It provides fast D and 3-D, analytical calculations of machine performance. Transformation of induction machine (IM) 2-D and 3-D geometry creation for detailed finite element calculations in ANSYS Maxwell is possible [1][2][4]. Sometimes the auto transfer of 2-D to 3-D and vice versa may be very difficult but with the aid of RMxprt, this can automatically generate a complete transfer of the 3-D or 2-D geometry, including all properties, to Maxwell for indept analysis finite element calculations. Widely used are the RMxprt and Maxwell software [8][16]. This has become an industrially acceptable standard [10][2]. 2.1 Double Cage Rotor Induction Motor Design with RMxprt Dual rotor cage induction motors have found its wide application in the industry globally and commercially due to its high starting torque and low current as well as its ability to operate maximally under variable and unstable load conditions [11][14]. By using RMxprt, a frame standard by IEC 60072-1 is defined; and a 7.5kW three-phase squirrel-cage induction motor is designed[15]. The parameters of the motor is given at Table 3. Table 3. Motor Design Parameter Parameters Outer Diameter of Stator Inner Diameter of Stator Number of Slots Outer Diameter of Rotor Inner Diameter of Rotor Number of Rotor Slots Rated Voltage Length of the motor Number of poles pair Dimension 174mm 106mm 36 102mm 36mm 28 240V 144mm 4 Figure 4: Ansys Maxwell geometry interface The modeled double cage rotor induction motor Ansys(Analysis System) Maxwell geometry work interface is clearly represented in figure 4. Figure 4, shows the Ansys(Analysis System)Maxwell interface during the design, simulation and rendering of the dual rotor cage induction motor from its original ordinary induction motor form. The figure 4 shows the cross sectional area of the modeled stator, rotor and its associated windings across the three phase A, B and C respectively. Induction motors are of great value to the global industry whose function cannot be ignored. Going into details to talk about the sample induction motor will be of no value if we do not consider the fundamentals of the induction motor. One of these fundamentals is the equivalent circuit and its associated parameters. Figure 5, shows the equivalent circuit of the induction motor. πΌ1 + πΌ21 π 1 π1 π21 πΌ0 π πΌπ πΌπ π 0 − Fig. 5: An equivalent circuit of an induction motor π 21 π Where πΌ1 is Stator current, πΌ21 the Rotor current referred to stator, π1 is the Stator reactance, π 21 = Variable load output π21 = Rotor reactance referred to stator πΌπ = Initial current πΌπ = Magnetizing current πΌπ = Electromagnetic current ππ = Initial reactance π π = Initial resistance Bound measurements are possible with RMxprt. In itself, RMxprt is a tool or a template base tool, hence seconds are used as time bound measurements. Table 4 below shows the RMxprt results for the modeled double cage rotor induction motor. π Electrical supply Table 3 RMxprt machine parameters Number of Revolutions Stator Phase Current Stator Resistance Torque Total losses Efficiency Output Power 1445RPM 12.05A 10245Ohm 36.1.Nm 1024.45KW 89.11% 6,0024KW Motor Bearings STATOR ROTOR-1 ROTOR- 2 Shaft-2 Shaft-1 Figure 6: Double cage rotor induction motor (DCRIM) 3.0 Analyzing the Double Cage Rotor Induction Motor Parameters Accurate depiction of the parametric components of an induction motor can be obtained through simulation [20][17][10]. The transient and steady state of the double cage rotor induction motor behaviour are made possible by simulating the properties of that motor. Once a change in reference frame is done, computational simulation by Ansys (Analysis System) Maxwell 2D and RMxprt software becomes easy [10][15]. The authors work shared that the Ansys(Analysis System) Maxwell 2-D software has the capability of modeling and simulating induction motors up to six phase. [5]. They showed that induction machines properly modeled can even have more than six phase yet the speed, torque and other characteristics are still accurately accounted for. Modeling induction motors as a pre-requisite for industrial recommendation is a necessity [6]. The figure 6 shows a typical block diagram of a double cage rotor induction motor.From the figure (6)above, the equivalent circuit for double cage rotor induction motor can be represented in the figure 7 Rs jXls JXlr,i0 + Rr0/s Ri/s JXlr,r0 jXir, i JXm Rr/erlsjXir,ri Figure 7: Equivalent circuit for double cage rotor induction motor 3.1RMxprt graphic plots and Results with Discussions After the simulation with the RMxprt tool, the following results were obtained graphically Figure 8: Torque performance for DCRIM Figure 9: Phase current performance of DCRIM From figure 8, the torque performance graph shows how the starting torque was high and then dies down and finally maintains stability across the plots and it can be seen in practical use of the sample induction motor. This result confirms the characteristics of the sampled induction motor as being consistent with the simulated model. According to the results plotted in figure 9, the phase current ranging from phase A, phase B and phase C maintained stability after being propagated across the performance plots during the running of the machine but at a point corresponding to the parameters variation it drops down and finally diminishes. This also validates the established characteristics performance of a double cage rotor induction motor in practice. Figure 10: Output power performance of DCRIM Figure 11: RMxprt interface for the moving torque As shown in figure 10, the output performance of the sampled induction motor as presented in the plots validates the performance index of real life situation of the double cage rotor motor. The aim of designing double cage rotor induction motor (DCRIM) is to surpass the limitations of the single cage which is to yield high performance with stable but improved conditions. This gives rise to reliability and dependability of the motor in question. 4.0 RMxprt interface of the simulated parameters In this process of modeling and simulation using the Maxwell 2-D with the imbedded RMxprt tool, it is therefore necessary to have a view of the interface use for the simulation of the various parameters and the results produced. From figure 11, the moving torque becomes high at starting then drops and rises again then it finally maintain stability across the simulated plots during the running of the machine with the RMxprt tool. This is with reference to the time variation with a uniform step-size of 0.001. Figure 12: The moving torque (Nm) of DCRIM against time (S) Figure 13: RMxprt interface in flux linkages in DCRIM From the figure 14, the flux linkage for phase A, phase B and phase C of the dual rotor cage induction motor (DCRIM) with its transient set ups. The flux; were evenly distributed across the three phases with a uniform linkage. This result is in consistency with the design motor parameters as well as the performance parameters of the modeled dual rotor cage induction motor in practice. Figure 15: RMxprt interface for the current windings Figure 14: Flux linkage in phase A, B and C in DCRIM Figure 16: Current windings for DCRIM According to the figure 16, the current windings for phase A, phase B and phase C was high at the starting and began to stabilized at 10s (ten seconds) and finally maintain uniform distribution from t=25s to t=200s. These results further ascertain the facts that dual cage rotor induction motor is more reliable than the single phase motor for its operations and functions in situations where high magnitude of current is needed for a start up. CONCLUSION This research paper was made possible with simulations tools like Ansys(Analysis System) Maxwell and the RMxprt. It covers a concept, a circuit model, a construction and expected experimental results of the sampled induction machine (DCRIM). The finite elements analysis method was used to implement it. The simulation result of the ordinary induction motor model and that of the double cage rotor model was compared, and these show that there is consistency between the introduced model and the selected motor parameters with respect to the results findings in torque rising from 0-1860N-m and fell uniformly over the range to 1680N-m, the phase current maintained stability in rising and the dropping completely; the output power performance increased uniformly from 1KW to 15KW all through the motor running process, the RMxprt current windings decreased from 12.7A to 6.7A during the process and across phase A, B and C. Simulating induction motors especially the double cage rotor type of motor is more precise with the use of the Ansys (Analysis System) Maxwell two dimensional (2-D) and RMxprt tools due to their electromagnetic influence. From the available results presented, it can be certain that simulating induction motors especially the double cage rotor type of motor is more precise with the use of the Ansys(Analysis System) Maxwell and RMxprt tools due to its electromagnetic influence. This shows that all parameters of the sampled induction motor can actually be modeled, simulated and modified. 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