class: center, middle # EE-564 Design of Electrical Machines ## Ozan Keysan [ozan.keysan.me](http://ozan.keysan.me) Office: C-113 <span class="meta">•</span> Tel: 210 7586 --- ### What do you need to know to design an electric machine? -- - ### Machine Type and type of construction -- - ### Rated Power (and power factor) -- - ### Rated Speed -- - ### Rated frequency/Number of Phases -- - ### Duty Cycle -- - ### Enclosure Class -- - ### Economics/Efficiency Requirement/Expected Life --- # Duty Cycle (Detailed info: texbook, pg.346) [Operating Graphs](http://myelectrical.com/Portals/0/Images/PostImages/IEC60034DutyCycle.gif) -- ### S1: Continuous running duty -- ### S2: Short-time duty (e.g. S2 10-90 min) -- ### S3: Intermittent periodic duty (eg. S3 25%) -- ### S4: Intermittent periodic duty with starting --- # Duty Cycle ### S5: Intermittent periodic duty with Electric Braking -- ### S6: Continuous operation periodic duty -- ### S7: Continous Operation Periodic duty with electric braking -- ### S8: Continuous Operation Periodic Duty with Related Load/Speed Changes --- --- # Dimensions to Choose? -- ### Diameter (Outer-Airgap) -- ### Airgap clearance -- ### Stator Stack Length -- ### Number of Stator/Rotor Slots -- ### Slot-Teeth Dimensions -- ### Winding Schematic --- # Where to start? --- # Where is the torque generated? -- ### Maxwell Stress Tensor (textbook pg. 33) ## \\(\sigma_F = \dfrac{1}{2}\mu_0 H^2\\) or ## \\(\sigma_F = \dfrac{1}{2\mu_0} B^2\\) --- # Where is the torque generated? ## Which direction does it rotate? -- <img src="./images/ee564/maxwell_tensor.png" alt="Drawing" style="width: 750px;"> --- # Shear Stress [More info](http://www.eleceng.adelaide.edu.au/research/power/pebn/pebn009%20sizing%20of%20electrical%20machines.pdf) -- ## Average Shear Stress Values -- - ### Industrial Motor (<1 kW): 0.7 to 2 kPa -- - ### Industrial Motor (>1 kW): 4 to 15 kPa -- - ### High Performance Industrial Servo: 10 to 20 kPa -- - ### Liquid Cooled Machines: 20 to 100 kPa --- # Electric- Magnetic Loading [More info](http://www.eleceng.adelaide.edu.au/research/power/pebn/pebn009%20sizing%20of%20electrical%20machines.pdf) -- ## Specific Magnetic Loading (T) -- ### i.e. average airgap flux density over a pole -- ## \\(\bar{B} = \dfrac{p \Phi_p}{\pi D_i L}\\) --- # Typical Flux Density Values <img src="https://raw.githubusercontent.com/ozank/ozank.github.io/master/presentations/images/magnetic_loading.png" alt="Drawing" style="width: 750px;"/> --- # Specific Electric Loading (kA/m) -- ## RMS ampere turns per unit lenght of the airgap -- ## \\(\bar{A} = \dfrac{ N\_{turn,slot} I Q}{\pi D\_i}\\) -- ### \\(N\_{turn,slot}\\): Number of turns per slot ### \\(Q\\): Number of slots ### \\(I\\): RMS current for wire --- # Typical Electric Loading Values <img src="https://raw.githubusercontent.com/ozank/ozank.github.io/master/presentations/images/electric_loading.png" alt="Drawing" style="width: 750px;"/> --- # Typical Tangential Stress Values <img src="https://raw.githubusercontent.com/ozank/ozank.github.io/master/presentations/images/tangential_stress.png" alt="Drawing" style="width: 750px;"/> --- ## Electrical & Magnetic Loading vs Stress -- ## Local tangential stress -- ## \\(\sigma\_{tan}(x) = A(x) B(x) \\) -- ## Average Stress ### \\(\sigma\_{tan}(x) = \dfrac{\hat{A} \hat{B} cos (\phi)}{2} \\) -- \\(= \dfrac{A\_{rms} \hat{B} cos (\phi)}{\sqrt{2}} \\) --- ## Torque vs Stress -- ## Torque = \\( \sigma\_{tan} r\_r S\_r\\) -- ## \\( T = \sigma\_{tan} r\_r (2 \pi r\_r l')\\) -- ## \\( T = \sigma\_{tan} 2 \pi r\_r^2 l'\\) -- ## \\( T = 2 \sigma\_{tan} V\_r \\) ## \\( V\_r \\) : Rotor Volume --- #Exercise: ### The diameter of a rotor of a 4 kW, 50 Hz, two-pole induction motor is 98 mm and the length is 82 mm. -- ### Assume 1% rated slip and calculate the machine constant and the average tangential stress. Textbook: Example 6.1 --- ## You can download this presentation from: [keysan.me/ee564](http://keysan.me/ee564)