Electromagnetics and Electric Machines Stefan Holst, CD-adapco
Overview Electric machines intro Designing electric machines with SPEED Links to STAR-CCM+ for thermal modeling Electromagnetics in STAR-CCM+
The Electrical Machine the basic definitions and function Basic definition: A motor is a machine that converts electrical energy into mechanical energy. A generator (also alternator or dynamo) is a machine that converts mechanical energy into electrical energy. This can be due to rotation or translation. A traction motor on a vehicle may perform both tasks. Electric motors and generators are commonly referred to as electric machines. Basic function: Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate an electromagnetic force.
The Electrical Machine the main parts A simple Electric motor has the following main parts: Rotor (turning part) carrying either an excitation DC winding or permanent magnets or a three phase winding or a squirrel cage or an armature winding Stator (fixed part) having a stator winding (single, 2-, 3-, n-phase) or exictation permanent magnets a commutator: a rotary mechanical switch, which reverses the current between the external circuit and the rotor along with the brushes, a shaft with bearings and bearing shields, a cooling system a housing
The Electrical Machine classification Electric machines may be classified by the source of electric power, their internal construction, their application, or the type of motion they give. They may be powered by direct current (DC), e.g., a battery powered portable device or DC source (rectified AC) or alternating current (AC) from a central electrical distribution grid or inverter.
The Electrical Machine Scale: From a few mw to several GW The smallest electric motors are mostly found on electric wristwatches. Medium-size motors of highly standardized dimensions and characteristics provide convenient mechanical power for industrial uses. The very largest electric motors are used for pipeline compressors, propulsion of ships and water pumps and of course as generators. Small watch motor vs. big hydroelectric generator mw & mm diameter Three Gorges Dam: 22,500 MW & several m dia.
SPEED What does SPEED has to do with electrical machines? SPEED is the leading design software for electric machines Detailed analytical analysis with finite-element links or finite-embedded solver for Motors, Generators and Alternators including inverters and other electronic controls Over 150 corporate accounts Over 1500 users A Worldwide CD-adapco Direct Sales Team and additional a Distributors Network including support Operating in all industrialized countries
The SPEED software programs The following machine types are available: brushless permanent magnet and wound-field AC synchronous PC-BDC induction PC-IMD switched reluctance PC-SRD direct current (PM) PC-DCM wound field and PM commutator PC-WFC
SPEED The design process 1 2 7 3 4 6 5 8
SPEED in use: Definition of the winding The winding editor
SPEED in use: The Template editor input data for calculation options, temperature, control parameters, etc.
SPEED in use: Graphical Output graphical feedback available range of
SPEED in use: Output design sheet large range of numerical values available
SPEED in use: GoFER Go to Finite-Elements and Return or use the embedded FE-solver directly (PC-BDC)
SPEED and STAR-CCM+ the combined workflow for Electrical Machines PC-FEA: Loss table calculation Reading the SPEED geometry and the loss distribution Running the final advanced thermal calculation. Initial design with SPEED Temperatures impact life time, reliability, cost & size
SPEED and STAR-CCM+ future: ELectrical MAchine Capability SPEED Development PC-FEA SPEED analytical STAR-CCM+ Development Analytical calculations Geometry templates of electrical machines Winding schemes Power electronic circuits Switch control Scripts to drive the EMAG/Thermal calculations ELMAC PC-FEA SPEED analytical STAR- CCM+ EMAG only STAR-CCM+ STAR-CCM+ 2D/3D EMAG THERMAL 2D/3D EMAG THERMAL time
STAR-CCM+ Electrical Machine Capabilities Geometry setup 2D to 3D extrusion Adding end winding Different rotor types Different machine types
STAR-CCM+ Electrical Machine Capabilities Symmetries and Periodicity
STAR-CCM+ Electrical Machine Capabilities Stator and rotor skewing Stator skewing Rotor skewing, stepped: linear, V:
STAR-CCM+ Electrical Machine Capabilities Simplified Winding for Cooling Simulations Tub end windings for Cooling Simulation for BDC Motor 20
What does low frequency EMAG mean Low frequency regime is valid for cases with t D J Displacement current t D = _t(εε) is growing with highly fluctuating fields Radar signals (low conduction current) Electric machines in contrast are driven by conduction currents STAR-CCM+ solves for potentials Formulation simplifies by using electric potential φ and magnetic vector potential A E = φ, B = curl A, and div A = 0 Transient mode, magnetostatic, and magnetostatic and motion
Solver Status v7.06 Formulation is validated for 2D simulations For transverse magnetics (current normal to simulation plane) equations reduce to solving for φ and A z In 3D simulation stability issues arise along magnetic to nonmagnetic material interfaces Proximity effect simulation in copper wire are possible Molten metal looses magnetic properties
Excitation Coils available in v8.02 Current driven simulation Magneto-static situation Current strength & orientation Modeling coil as bulk region Orientation given by contour Winding parameter Number of Turns multiplied by Electric Current defines applied current density Post processing Specific Magnetic Flux linkage FF Volume integral delivers flux linkage of region
Link to other physics model in STAR-CCM+ Electrically conducting fluids Magneto hydrodynamics Plasma simulation Mixing of molten metal STAR-CCM+ v8.02 will bring one way coupling Given magnetic field forces as momentum source for the fluid Hartmann channel validation Magnetic flux aligned to y-axis leads to secondary flow pattern For strong B-field, velocity profile looks like in turbulent flow (more mixing)
Lorentz force acting on charged particles Lorentz force currently requires field function cross($$magneticfluxdensity,$$velocity) cross($$magneticfluxdensity,$$particlevelocity) For Lagrange phases this is specified as an external force field Applications Particle tracing due to field change CRT
Coupling field and circuit simulation Electromagnetic field calculations are costly Circuit modeling helps reducing the EMAG simulation domain considerably Electric machines can for the most part be simulated in 2D in the design stage of product development Circuit modeling will deliver currents to be applied in the winding regions Field simulation provides flux linkages Applied voltages are an input parameter or stem from more complex controller models
Coupling STAR-CCM+ to Simulink /MATLAB Simulink is a block diagram environment for designing general control flow diagrams including electrical circuits Simulink handles discrete or continuous states Continuous state handling is needed for the circuit coupling Model is transferred internally into a differential algebraic equation Solution method can be auto-selected or user specified Transient STAR-CCM+ can provide individual post-processed values at every time step Supply of flux linkage Ψ I or even its time derivative ( t Ψ) I Data exchange via minimal exchange protocol, transmitted over TCP connection between programs, Allows running Simulink and STAR-CCM+ on different machines
Protocol Design Start simulation Open port Specify reports Specify input: field functions time step size Update circuit time step Macro connects to Simulink port Store list of reports Run Step Send reports
Test case
Coupling STAR-CCM+ to Simulink /MATLAB Simulink data enters STAR-CCM+ via Java Macro scripting Macro listens for input parameters Field Function,CurrentPhase1,<0.3 A> Field Function,CurrentPhase2,<0 A> Field Function,CurrentPhase3,<10.3 A> Step protocol element leads to time step with a specified size (0.1s) Step,0.1 The STAR-CCM+ representation within Simulink Level 2 Matlab functions Provides function hooks for link initialization and data update Matlab language easily interfaces with Java one language protocol implementation STAR-CCM+ provides state value X S directly in SI units Report,FluxLinkagePhase1,0.7 In Continuous state integration Simulink requires derivative at each time step Derivative is calculate with respect to last Simulink value X M as (X S X M )/dd
Coupling Summary STAR-CCM+ and Simulink communicate over sockets Offers continuous state coupling of field simulation to circuit Explicit Euler Simulink solver needed Current approach only uses scripts Soon on http://javahut.cd-adapco.com Protocol extends to any application Anything in STAR-CCM+ that can be defined as a field function can be an input Any report value can be an output to Simulink/Matlab