Seismic qualification of Heat exchanger

heat-exchanger1ProSIM is an approved engineering consultant with DAE (Department of Atomic energy) entities in India such as NPCIL, IGCAR, BARC, BHAVINI working along with their major EPCs and their vendors. Internationally, ProSIM is a part of ITER-IO projects via ITER-IN/EPC contractor.

ProSIM has worked on design evaluation of various systems/components in a nuclear power plant (Seismic Design Verification) as per various codes (ASME, RCCMR, API, BP, ANSI etc).

heatexchanger2ProSIM has developed macros/ scripts for the Seismic Design Verification of all safety and seismic classes, including NINS of nuclear equipment (active/passive). ProSIM has experience in both OBE (Operating Basis Earthquake) and SSE (Safe-Shutdown Earthquake) methods for Seismic Design Verification, based on requirement – either FRS (Floor response spectra) or equivalent static methods using FEA based software.

ProSIM expertise includes Seismic evaluation (seismic structural integrity) as per ASME codes (Section III, Subsection NB, NC, ND, NF etc), IS1893 or similar codes; seismic design optimization to enable the design pass the seismic evaluation, modify the design to suit the site conditions, generate reports as per requirements of operators (such as NPCIL or ITER or BHAVINI); provide clarifications to regulatory agencies (such as AERB) for design documents.

ProSIM has worked on several packages of nuclear power plants (nuclear structural integrity assessment) including BOTIP, STG, Turbine, CS, PPP, Switchyard, C&I, IDCT, NDCT etc. ProSIM has worked on several hundreds of projects in various systems and subsystems and equipment.

Gravity analysis

heatexchanger3The gravity analysis is performed to know the behaviour of the heat exchanger for its own weight. This is a part of the seismic evaluation. The response of the heat exchanger for gravity load is done by static analysis.

Design Pressure analysis

The design pressure analysis is performed to capture the effect of the maximum pressure exerted by the fluid. The static analysis is carried out to know the response of the heat exchanger. This load case is combined dead weight and seismic loads to perform the Seismic Design Verification.

Seismic analysis

Seismic analysis is performed to capture the behaviour of a heat exchanger for earthquake load. Both operational basis earthquake (OBE) and Safe shutdown earthquake (SSE) will be considered for seismic design verification.

The first natural frequency is more than the cut-off frequency, the floor response spectra analysis will be ruled out and equivalent static analysis will be performed. The load combinations are done for various service levels. The stress value is compared with the allowable limits and henceforth the seismic qualification is done.

Thermal analysis

The fluid inside side heat exchanger will be carrying some amount of temperature. The stresses and displacement developed by the temperature are captured by thermal analysis.

Seismic Qualification

The respective loads are combined with seismic loads and seismic qualification is done. The heat exchanger has several components. Each component is qualified for seismic load combinations.

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Iron Losses Prediction in BLDC Motor

Demand for higher efficiency, low volume, low cost, noiseless and smaller size in motors has grown from the need to incorporate in their designs. In order to meet this demand, motors have to improve their output density and reduce their losses. One type of loss commonly found in motors is an iron loss, which increases drastically at high rotation speeds and high magnetic flux densities. This increase can lead to a rise in temperature and a reduction in efficiency. Consequently, it is more important to predict an iron loss at the motor design stage itself.

Unfortunately, it is not possible to obtain iron losses accurately in studies that use the magnetic circuit method or thumb rules. In order to obtain them accurately, one needs to find the distribution and time variations of the magnetic flux density in each part of the motor after accounting for a fine geometry and the material’s nonlinear magnetic properties. Using the finite element method (FEM) is essential in order to carry out this kind of a detailed analysis.

To know about detailed FEA modelling of BLDC motor to predict the material saturation and accurate iron loss prediction, please attend the BLDC motors and Controllers workshop.

BLDC Motors and Controllers (Design Verification & Validation – FEM analysis – Optimisation)

Date: 8th & 9th November 2017

VENUE: Bhaskara Seminar Hall, AICTE HQ, Nelson Mandela Road, Vasant Kunj, New-Delhi

For more details contact:    

Soumya: 9900067486 / soumya.k@pro-sim.com,
Ashwini: 9972304448 / ashwini.j@pro-sim.com,
Suma     : 080-23323020 /41277792 (ext: 109) / suma.k@pro-sim.com

Posted in JMAG Tagged with: , , , ,

Seismic qualification of Cable Tray Support Structure

seismic-cabletray1ProSIM is an approved engineering consultant with DAE (Department of Atomic energy) entities in India such as NPCIL, IGCAR, BARC, BHAVINI working along with their major EPCs and their vendors. Internationally, ProSIM is a part of ITER-IO projects via ITER-IN/EPC contractor.

ProSIM has worked on design evaluation of various systems/components in a nuclear power plant (Seismic Design Verification) as per various codes (ASME, RCCMR, API, BP, ANSI etc).

seismic-cabletray2ProSIM has developed macros/ scripts for the Seismic Design Verification of all safety and seismic classes, including NINS of nuclear equipment (active/passive). ProSIM has experience in both OBE (Operating Basis Earthquake) and SSE (Safe-Shutdown Earthquake) methods for Seismic Design Verification, based on requirement – either FRS (Floor response spectra) or equivalent static methods using FEA based software.

ProSIM expertise includes Seismic evaluation (seismic structural integrity) as per ASME codes (Section III, Subsection NB, NC, ND, NF etc), IS1893 or similar codes; seismic design optimization to enable the seismic evaluation, modify the design (seismic design optimization) to suit the site conditions, generate reports as per requirements of operators (such as NPCIL or ITER or BHAVINI); provide clarifications to regulatory agencies (such as AERB) for design documents.

ProSIM has worked on several packages of nuclear power plants (nuclear structural integrity assessment) including BOTIP, STG, Turbine, CS, PPP, Switchyard, C&I, IDCT, NDCT etc. ProSIM has worked on several hundreds of projects in various systems and subsystems and equipment (Nuclear power plant active and passive types of equipment).

ProSIM has the ability to qualify Cable tray support structure for all types of application, Seismic Design, shape, size and MOC. It also includes cable tray support system of all safety class (Class 1 to NINS).

FEA tools like ANSYS & Abaqus are used to analyse the response of the cable tray support structure for various individual static and dynamic loads (floor response spectra). These loads are combined as per prescribed service levels and checked against the prescribed factor of allowable.

This document gives a description of Seismic evaluation of the cable tray support system.

Dead Weight analysis

The dead weight analysis is performed to capture the behaviour of the support structure for own weight. The static analysis is used to capture the behaviour of self-weight. This analysis is used to combine with seismic loads.

Live Load analysis

The live load analysis is performed to capture the behaviour of the support structure for own weight with the weight of the cable. The static analysis is used to capture the behaviour of live load analysis. These live loads are combined with dead weight and seismic loads and the seismic evaluation is done.

Seismic Load analysis

Seismic analysis is performed to capture the behaviour of a cable tray support structure for earthquake load. Both operational basis earthquake (OBE) and Safe shutdown earthquake (SSE) will be considered. The FRS ( floor response spectra) is given as input for seismic excitation. The first natural frequency is more than the cut-off frequency, the FRS analysis will be ruled out and equivalent static analysis will be performed. The load combinations are done for various service levels.

The stress value is compared with the allowable limits of ASME section 3 division 1subsection NF and henceforth the seismic qualification is done. For the support structure, buckling effect will be considered. The nuclear structural integrity assessment is done as per the mentioned codes. The respective customised sheets will be used to perform seismic qualification.

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Evaluation of Performance Characteristics of BLDC motors

BLDC motors are used in hybrid and electric vehicle drives, home appliances, and a host of industrial applications. BLDC motors are high-performance motors, providing high toques at a wide range of speeds, and running at high efficiency.   BLDC motors become natural choice of designers when the application calls for high reliability, high efficiency and high power-to-volume ratio.

Performance characteristics of motors depict the relationship between torque, speed, efficiency, current, power, all of which are interconnected.

A permanent magnet synchronous motor’s characteristics are highly susceptible to saturation effects in the motor’s magnetic circuit. Using finite element analysis (FEA) tools such as JMAG, saturation effects can be considered in the magnetic analysis. This helps to predict accurately the torque-current behaviour of the BLDC motors. As seen in the figure below, the torque- current relation is linear up to the certain level of current. After a certain level, the magnetic saturation effects start dominating, and the torque starts to drop off till the torque-current curve becomes nearly asymptotic.  Using JMAG express, all the performance characteristics can be quickly evaluated for a given design of the motor. Design parameters can be varied to achieve desired results.

Once the desired performance is realised, the ‘shortlisted’ design can be taken up for more detailed and rigorous design verification by simulation. Further, such a procedure will also lead to design optimisation. All these exercises are conducted in a virtual environment and hence no cost on physical prototyping and physical testing is involved.   Typically, a design is evaluated and optimised with a matter of few days to a couple of weeks.

bldcmotors-1

bldcmotors-2

More details of the design of BLDC motors are covered in the workshop on
BLDC Motors and Controllers (Design – Verification & Validation – FEM analysis – Optimisation)

Date: 8-9 Nov 2017,
VENUE: Bhaskara Seminar Hall, AICTE HQ, Nelson Mandela Road, Vasant Kunj, New Delhi

Contact for more details:
Ashwini: 9972304448 | ashwini.j@pro-sim.com
Suma : 080-23323020 /41277792 (ext: 109) suma.k@pro-sim.com

Visit our web pages for additional information:

Posted in JMAG, Motors Tagged with:

Simulating The Effect Of Chemical Composition & Pouring Temperature Variations On Casting Quality

ProSIM has supported Casting companies to convert casting component from Conceptual design stage to market stage

  • To develop methods/gating systems in a faster and economical manner.
  • To increase yield and reduce rejections.
  • To improve the quality of the component.
  • To improve the productivity of process and other resources
  • To develop process control maps by sensitivity analysis.
  • To assimilate casting simulation technology in their design and development practice.

Design of Experiment (DOE) is a formal mathematical method for systematically planning and conducting scientific studies that change experimental variables together in order to determine their effect on a given response.

In this case study, we have conducted sensitivity analysis. Here, we are able to study the soundness of the casting by studying the process parameters and material properties, by varying the pouring temperature. Thus getting a clear insight on how to obtain a sound casting.

  • The case study was carried out by varying the pouring temperature.
  • ADSTEFAN users are trained to conduct sensitivity analysis, to determine optimum process window.
  • Objective of this study is to predict soundness of casting due to change in Pouring Temperature (5 cases)

Approach for casting simulation as follows

  • Converting the CAD model to mesh
  • Setting casting conditions in simulation model (pre-processing)
  • Specification of material grade for component and moulds
  • Specification of in-gate velocity
  • Specification of casting temperature, mould temperature
  • Melt flow simulation (mould cavity filling).
  • Solidification simulation.

casting-1

Below mentioned are the details of input provided for carrying out the analysis for the given component.

Process

Sand Casting

Pre-processing inputs

3D CAD (STL) Model

Casting material – FCD 500 (SG iron)

casting-2

FLUID FLOW ANALYSIS Temperature Distribution:

casting-3

Inference: Images show the temperature distribution for Case1, Case 2, Case 3, and Case 4 & Case 5.

From the images, it can be inferred that the temperature drop observed is still above the solidus.

Fluid Flow Analysis (Air Entrapment)

casting-4

Solidification Analysis (Progressive Solidification)

casting-5

Inference: – The picture shows the final stage of solidification. There are few discontinuities observed in the casting during solidification process as highlighted in the image and these regions may lead to shrinkage porosity defects.

Solidification Analysis (Shrinkage porosity)

casting-6

Inference: Possibility of shrinkage related defects as highlighted in the above figure.

Results and discussions

Casting simulations software is used to study the effect of pouring temperature variation and its effect on the quality of the casting is studied. Each temperature case has its own characteristic results and the parameters are needs to be optimized according to the foundry operational conditions.

 

Posted in Casting Tagged with: , , , , ,

Stray Capacitance Analysis of an IPM motor using FEM

Abstract

An Interior permanent magnet (IPM) motor is a combination of a Permanent magnet synchronous motor and switched reluctance motor. The permanent magnets (PM’s) are buried inside the rotor. These motors are highly suitable for a wide verity of industrial applications such as Robotics, Automotive etc. In these applications, demand for motor higher efficiency, reliability and long life is increasing. One of the factors that affect this parameter is stray capacitance. In this article, it is explained how to obtain the Stray Capacitance between the stator core and stator coil, stator core and rotor core, inner and outer ring of the bearing using Finite Element Analysis.

Introduction:

In 1950, ferrite magnets and rare earth magnets have been invented and these magnets having the stronger magnetic force and it became commercialized. The significantly improved in motor drives for controlling the speed of the permanent magnet motors and brought them to be high-performance with better efficiency motors. In recent decade huge improvement in control technologies supported the development of the IPM motor. This type of IPM motor is highly efficient and provides variable-speed operation for a wide range of applications. Figure 1 shows the 4 pole IPM motor considered for finite element analysis. The IPM motor has two main parts, Stator part and rotor part. The stator consists of stator core and coils. The rotor consists of the rotor core and permanent magnets.

stray-capacitance1

Figure 1. Interior Permanent Magnet Motor

Bearing: The most commonly-used ball bearing called a deep groove ball bearing is employed. A deep groove ball bearing generates little friction torque and is suitable for a fast-rotating part or for an application that requires low noise and vibration. Figure 2 shows the structure of bearing.

stray-capacitance2

Figure 2. Bearing

What is Stray Capacitance?

Stray capacitance is unpremeditated and unwanted capacitance exists between surfaces. Capacitance doesn’t exist only within capacitors but it can occur between the parts, that is proximity to each other. Stray capacitance results in a disturbance of normal current flow within the surface.

Methodology

Electrostatic Analysis is carried out for 4 poles 12 slot IPM motor to obtain the stray capacitance between different parts of the motor.

For the analysis, 3D model is imported to the JMAG Designer. Further preprocessing is done in JMAG designer (assigning materials, boundary conditions such as electric potential boundary to specify electric potential between parts, surface charge to obtain the charge on a specified boundary and mesh modelling). In this FEM analysis, 1 Volts is applied between the two parts for which surface charge Q is induced on the surface of each part and finally obtained the stray capacitance.

Analysis Results:

Figure 1 shows the contour plot of electric field distribution between the stator core and stator coil. Figure 2 shows Electric field distribution between stator and rotor core and figure 3 shows the Electric field distribution between inner and outer rings of bearing. From these contour plots, it is observed that large electric field is induced in the air (I.e. gap between the parts) .

stray-capacitance3

Figure 3 Electric field distribution between Coil and Stator core

stray-capacitance4

       Figure 4 Electric field distribution between Rotor core and Stator core

stray-capacitance5

Figure 5 Electric field distribution between Inner and Outer rings of the Bearing

Stray capacitance:

The Stray capacitance between the motor’s coil and the stator core, between the motor’s rotor core and stator core and between inner and outer rings of the bearings is indicated in table 1. In this article, Stray Capacitance is calculated using the formula C=Q/V.

stray-capacitance6

Conclusion

The electrostatic analysis is carried out to obtain stray capacitance in IPM motor using JMAG software. Stray capacitance can be calculated manually but it difficult to get accurate results and also increases the number of prototyping, time and cost. JMAG provides accurate results and gives the clear visualization of electric field distribution between the parts of the motor as shown in contour plots. From the results, it is concluded that electric field distribution is high at the gap between surfaces of the two parts. The results are shown for applying 1 volt but in JMAG multiple cases can be simulated by varying the voltage which reduces the number or prototyping, cost and time. These multiple cases give one best solution that can be practically implemented.

ProSIM has vast experience in using JMAG simulation software to analyze all type of electrical machines (AC or DC machines). JMAG has the capacity to understand the complex internal physical phenomena of equipment while performing high speed of analysis. JMAG applies the latest techniques to accurately model complex geometries, thermal and structural phenomena associated with electromagnetic fields.

Posted in JMAG, Motors Tagged with: ,

Seismic qualification of Diesel Generator Set

seismic-diesel1ProSIM is an approved engineering consultant with DAE (Department of Atomic energy) entities in India such as NPCIL, IGCAR, BARC, BHAVINI working along with their major EPCs and their vendors. Internationally, ProSIM is a part of ITER-IO projects via ITER-IN/EPC contractor.

ProSIM has worked on design evaluation of various systems/components in a nuclear power plant (Seismic Design Verification) as per various codes (ASME, RCCMR, API, BP, ANSI etc).

seismic-diesel2ProSIM has developed macros/ scripts for the Seismic Design Verification of all safety and seismic classes, including NINS of nuclear equipment (active/passive). ProSIM has experience in both OBE (Operating Basis Earthquake) and SSE (Safe-Shutdown Earthquake) methods for Seismic Design Verification, based on requirement – either FRS (Floor response spectra) or equivalent static methods using FEA based software.

seismic-diesel3ProSIM expertise includes Seismic evaluation (seismic structural integrity) as per ASME codes (Section III, Subsection NB, NC, ND, NF etc), IS1893 or similar codes; seismic design optimization to enable the seismic evaluation, modify the design (seismic design optimization) to suit the site conditions, generate reports as per requirements of operators (such as NPCIL or ITER or BHAVINI); provide clarifications to regulatory agencies (such as AERB) for design documents.

seismic-diesel4ProSIM has worked on several packages of nuclear power plants (nuclear structural integrity assessment) including BOTIP, STG, Turbine, CS, PPP, Switchyard, C&I, IDCT, NDCT etc. ProSIM has worked on several hundreds of projects in various systems and subsystems and equipment (Nuclear power plant active and passive types of equipment).

ProSIM has the ability to do seismic qualification of Diesel Generator set for all types of application, Seismic Design, shape, size and MOC. It also includes Diesel Generator set of all safety class (Class 1 to NINS).

FEA tools like ANSYS & Abaqus are used to analyse the response of the Diesel Generator set for various individual static and dynamic loads (floor response spectra). These loads are combined as per prescribed service levels and checked against the prescribed factor of allowable.

This document gives a description of Seismic evaluation of the Diesel Generator set.

The DG set consists of four major assemblies;

  1. Diesel Engine
  2. Flywheel and coupling assembly
  3. Alternator
  4. Base Frame

The parts which have modelled for FE analysis are;

  1. Base Frame (Skid)
  2. Engine crankcase
  3. Alternator assembly
  4. Turbocharger
  5. Turbocharger support
  6. Crankshaft
  7. Bearing assembly
  8. Flywheel and coupling
  9. Oil Sump

The beams, mass, shell and solid elements are used to FE model of the Diesel Generator set. The Diesel Generator set is qualified for seismic design verification, both static and dynamic loads (Seismic loads) and the respective load combinations.

The various loads for the qualification of DG set are;

  • Dead weight
  • Engine dynamic loads
  • Alternator normal torque
  • Short circuit load
  • Earthquake Load
    1. Operational basis earthquake
    2. Safe shutdown earthquake

Based on the service levels, the load combination is done and the seismic qualification is done as per French standards RCC-M.

Functional Operability

Functional operability is performed to check the misalignment between stator and rotor. The checking of the gap between the rotor and stator part of alternator, engine crankshaft is done. The obtained value is checked against the allowable. This is a part of seismic structural integrity.

Bearing Stiffness Calculation

Bearing stiffness evaluation data is taken from Jeumont Electric lateral analysis -REINK bearings document No. 6SC26617, Rev B. The calculation is done with respect to, prescribed formulae. The bearing stiffness is calculated for the alternator and engine thrust bearing.

Seismic analysis

The response of the DG Set to the earthquake loading is captured by seismic analysis (Floor Response Spectra). The analysis is done for both operational basis earthquake (OBE) and safe shutdown earthquake (SSE), for the given floor response spectra as input to Seismic Excitation. The seismic loads added/subtracted to the other loads like dead weight, design pressure, engine dynamic forces etc., to know the response of the exhaust system and the Seismic qualification is done. The respective customised sheets are used for the seismic qualification which reduces error, time consumption and manpower.

Posted in Energy Tagged with: , ,

Seismic Qualification of Piping Support System

piping-system1ProSIM is an approved engineering consultant with DAE (Department of Atomic energy) entities in India such as NPCIL, IGCAR, BARC, BHAVINI working along with their major EPCs and their vendors. Internationally, ProSIM is a part of ITER-IO projects via ITER-IN/EPC contractor.

ProSIM has worked on design evaluation of various systems/components in a nuclear power plant (Seismic Design Verification) as per various codes (ASME, RCCMR, API, BP, ANSI etc).

ProSIM has developed macros/ scripts for the Seismic Design Verification of all safety and seismic classes, including NINS of nuclear equipment (active/passive). ProSIM has experience in both OBE (Operating Basis Earthquake) and SSE (Safe-Shutdown Earthquake) methods for Seismic Design Verification, based on requirement – either FRS (Floor response spectra) or equivalent static methods using FEA based software.

piping-system2ProSIM expertise includes Seismic evaluation (seismic structural integrity) as per ASME codes (Section III, Subsection NB, NC, ND, NF etc), IS1893 or similar codes; seismic design optimization to enable the design pass the seismic evaluation, modify the design to suit the site conditions, generate reports as per requirements of operators (such as NPCIL or ITER or BHAVINI); provide clarifications to regulatory agencies (such as AERB) for design documents.

ProSIM has worked on several packages of nuclear power plants (nuclear structural integrity assessment) including BOTIP, STG, Turbine, CS, PPP, Switchyard, C&I, IDCT, NDCT etc. ProSIM has worked on several hundreds of projects in various systems and subsystems and equipment.

ProSIM has the ability to qualify piping support systems of all types, application, design, shape, size and MOC. It also includes piping support systems of all safety class (Class 1 to NINS).

FEA tools like ANSYS, Abaqus & STAAD Pro are used to analyse. The response of the piping support system for various individual static and dynamic loads (floor response spectra). These loads are combined as per prescribed service levels and checked against the prescribed factor of allowable.

This document gives a description of the seismic evaluation of the piping support system.

Dead Weight analysis

The dead weight analysis is performed to capture the behaviour of the piping support structure under self-weight. This is one of the individual load case for the Seismic Design Verification. The mass of the pipe is also considered. The static analysis is used to observe the response of the support structure under dead load.

Live Load analysis

The support structure, along with dead load should also sustain other loads like snow, dust, sodium loads, any things kept on the support structure. These loads are known as live loads. The combination of dead load and live loads is used for Seismic evaluation. A static analysis is used to capture the effect of live load on the structure. Live loads will be applied on the platforms as joint loads on the supporting members. These imposed loads are calculated based on the provisions of IS 875 (part II)-1987 and IS 6533 Part 2 1987.

Wind Load analysis

Since the lattice tower is exposed to the environment, the blowing of wind will affect the structure. The response of the support structure for the wind load will be captured by wind load analysis. This analysis is a part of seismic structural integrity. All structures will be designed for strength and serviceability for this level of wind. The wind load is calculated by using GEF method as per IS 875 (Part 3) Clause 8.

 Seismic analysis

Seismic analysis is performed to capture the behaviour of support system for earthquake load. Both Operational Basis Earthquake (OBE) and Safe Shutdown Earthquake (SSE) will be considered for Seismic Design Verification. Response spectrum analysis (floor response spectra) is given as input for seismic excitation.

Deflection and stress for the structure is captured for load combinations as per various service levels. The stress value is compared with the allowable limits and Seismic Design Verification is done.

Seismic Qualification

The load combination (dead load, live load, wind load and seismic loads) is done as prescribed by the service levels. Various load factors is considered for service levels for worst loading conditions. The obtained stress value is compared with the allowable values of IS 800-1984 clause 5.1.1 and AERB/SS/CSE-2.

Posted in Energy Tagged with: , , ,

Shrinkage Defect in Casting

Shrinkage defects can occur when standard feed metal is not available to compensate for shrinkage as the thick metal solidifies. Closed shrinkage defects, also known as shrinkage porosity, The Isolated pools of liquid from inside solidified metal, which is called hot spots. The shrinkage defect usually forms at the top of the hot spots. They require a nucleation point, so impurities and dissolved gas can induce closed shrinkage defects.

The defects are broken up into macroporosity and microporosity (or micro shrinkage), where macro shrinkage can be seen by the naked eye and micro shrinkage cannot.

Shrinkage defects can be split into two different types: open shrinkage defects and closed shrinkage defects.

Open shrinkage defects are open to the atmosphere, therefore as the shrinkage cavity forms air compensates. There are two types of open-air defects: pipes and caved surfaces. Pipes form at the surface of the casting and burrow into the casting, while caved surfaces are shallow cavities that form across the surface of the casting.

Types of Casting Shrinkage

There are four types of shrinkage that can occur in metal castings: cavity, sponge, filamentary, and dendritic shrinkage.

• Cavity shrinkage: This defect occurs when two different sources of molten material are joined to create a common front while solidification is already taking place. A lack of additional feed material to fill in the accumulating gaps can further exacerbate the cavity shrinkage problem.

  • Sponge shrinkage: This usually arises in the thicker mid-section of the casting product and causes a thin lattice texture similar to filament or dendrites to develop.
  • Filamentary shrinkage: This results in a network of continuous cracks of various dimensions and densities, usually under a thick section of the material. It can be difficult to detect, and the fracture lines tend to be interconnected.
  • Dendritic shrinkage: Dendritic fractures are narrow, randomly distributed lines or cavities that are often unconnected. They are typically thinner and less dense than filamentary cracks.

How Macro porosity (shrinkage defect) occurs? What are the reasons?

  • Insufficient metal available to feed the hot spot in the casting
  • Inadequate gate & riser
  • Improper directional solidification.

casting1

casting2

Image: 2 (Macro Shrinkage defect)

How can Macro porosity (shrinkage defect) be eliminated?

  • Provide sufficient gate, riser near hot spot region
  • Provide chills, coatings
  • Use proper inoculants

Use Exothermic/Insulating sleeve to increase riser effectiveness

How Microporosity (shrinkage defect) occurs? What are the reasons?

  • Network of the small voids distributed through the casting due to local solidification in dendrite structure
  • Long freezing range of the alloy
  • Mold or casting temperature is low.
  • Long freezing range of alloy
  • Low-temperature gradient

casting4

                             Image: 3 (Micro porosity)

How can Macro porosity (shrinkage defect) be eliminated?

  • Preheat the die to 180 -250 Deg
  • Preheat the sand mould to 60 Deg.

Adstefan (Casting Simulation Software)

  • Adstefan can predict shrinkage along with size and volume can be identified.
  • Riser dimensions modified to feed the shrinkage porosity volume shown in adstefan.
  • Predict these defects. This will help the designer to eliminate the microporosity by reducing the cooling rate.

Shrinkage Porosity analysis : 

The image 2 & 3 shows the shrinkage present in the component. These shrinkages are due to lack of molten metal in the riser to feed the casting during solidification. The shrinkages are present all along the component surface as shown. Shrinkages present in red are of considerable volume.

Posted in Casting Tagged with: , ,

Static performance analysis of Switched Reluctance (SR) Motor using Finite Element Analysis

Abstract

Currently, Switched Reluctance motors are mainly used in the field of electric traction and other industrial areas due to its various advantages like high power density and better efficiency for higher speed, high reliability, high starting capabilities, simple and robust construction because rotor has no windings, no slip rings and no brushes which leads to less maintenance and it can be operated at high temperature. The main objective of this article is to evaluate the effect on inductance and torque for each rotor position and flux linkage by varying the flow of current in the circuit.

Introduction

motor-1

Figure 1: Switched Reluctance Motor Model

SR Motor has a simple structure that greatly simplifies the mechanical design since there is no need to supply power to the rotor. As shown in above figure1 SR motor has two main parts; one is stator part and rotor part. It has a stator with the power supply windings and the rotor core is composed of soft magnetic materials such as laminated steel. This type of construction has different working functions for different operating modes as explained below.

Working

A Switched reluctance motor works on the principle of magnetic reluctance i.e. the resistance offered by a material for a magnetic field. In this motor the rotation produced depends on the reluctance offered by the rotor to the stator magnetic field.

The stator of a switched reluctance motor has wound field coils and it also has a salient pole (projecting pole) type rotor with no magnets but soft magnetic materials like laminated steel. When the stator of the SRM is energized the magnetic reluctance of the rotor produces a force that helps in aligning rotor to the nearest stator pole. In order to maintain this rotation, a control circuit is used to switch in between the windings of the stator poles, so as to maintain the stator magnetic field leading the rotor poles and pulling them forward.

The switching or control circuit makes use of a rotor position sensor (electronic) in order to enable accurate switching in between the stator poles based on the rotor position, producing a smooth rotating motion. The rotor position sensors can also be used for accurate stepping actions.

The power to the stator windings can be given through a number of ways but the most commonly used approach is the use of an asymmetric bridge converter. The three phases of an asymmetric bridge converter are actuated according to the required phase sequence of an SRM.

Finite Element Analysis of Switch Reluctance Motor

Electromagnetic analysis has been carried out for 4 pole, 6 plots SR motor using JMAG software.

Figure 1 shows the 2D model of SR motor considered for the analysis. 2D cad model is imported from cad editor to perform the analysis. The suitable material has been assigned to each part of the motor. Boundary conditions such as motion condition (to specify rotating parts), torque condition (to obtain torque), and fem coil condition (to apply coil connection) is assigned. Model meshes before the analysis are shown in figure 2.

motor-2

Figure 2: 2D model of SR Motor

motor-3

Figure 3: Mesh Model

Meshing is a discrete representation of a model using partial differential equation. The finite element mesh is used to subdivide the model into smaller domains called elements over which a set of equations are solved. JMAG defiantly consider the triangular type of mesh element.

Results

  • Magnetic Flux Density Distribution for different current

motor-4

Figure 4: Magnetic flux density distribution for different current

From the contour plot, it is observed that the variation in the magnetic flux density by changing the current from 2 amps to 10 amps.

Flux Linkage

From the below figure we can understand that when the angle is in the range of 45 degrees the tooth is facing to each other and the magnetic flux linkage will be increased which increases the current.

motor-5

Figure 2: Flux Linkage Waveform

Inductance Waveform

  • From the below figure we can understand that when the current value increases, that is when the value of angle increases the value of inductance is been reduced.

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Figure 3: Inductance Waveform                                         

Torque

  • From the below figure we can understand the approximate average torque for each current value.

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Figure 4: Torque Waveform           

Advantages and Disadvantages of SR motor

Advantages:

  • SRM is simple in construction and highly suitable for high-speed applications.
  • Does not involve any permanent magnets hence economic and no deterioration in magnetic properties
  • The absence of commutator reduces complexity in construction which reduces the friction loses and sparking in the rotor.
  • The variable frequency drives employed in an SRM are less complex than conventional ones.

Disadvantages:

  • The operation of an SRM is noisy and not suitable for low-speed operations.
  • SR motor torque has ripple
  • It requires a switching and control circuits which are complex.

Conclusion

Static performance analysis of Switched reluctance motor is carried out in the software called JMAG. JMAG is an FEA software Finite element method accurately calculates physical phenomena of electromagnetic devices. Electromagnetic analysis has been simulated for different cases of current varying from 2 amps to 10 amps. The results for different cases have been observed when the rotor is rotating in the range of 0 deg to 45 deg, the tooth of the stator and rotor face each other. From the results, it is observed the effect of inductance and torque for change in each rotor position and flux density by varying the current. Instead of using the linear equation for actual calculation which increases the time and complexity, virtual testing can be done by JMAG software which gives a clear picture of magnetic flux density distribution, flux linkage, torque and inductance easily within a short duration. It also reduces the number of prototyping and also provides accurate results.

ProSIM has vast experience in using JMAG simulation software to analyze all type of electrical machines (AC or DC machines). JMAG has the capacity to understand the complex internal physical phenomena of equipment’s while performing high speed of analysis.

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