Electrical Machines
Questions & Answers
Please select the coreect trand for the back-EMF(E) as field current (lf) charcateristic of a brushed DC machine under no load test (open-circuit test). Rising lf is performed before falling lf.
Three phase, 480V 40 Hz, 6 pole induction motor R_{1}=R_{2}^{\prime}=0.1 \Omega, X_{1}+X_{2}^{\prime}=X_{e q}=0.5 \Omega Full load slip is 3% η = 90% Starting current (ignore magnetizing current) b. Starting torque c. Maximum torque d. Rotor resistance to be added to the rotor circuit to reduce the starting current by 50% e. Starting torque at case d. f. Rotor resistance to be added to the rotor circuit to increase the starting torque tomaximum g. Starting current at f.
Discuss the mitigation PV penetration.measures for high voltage and low voltage impacts of
An 'iron ring has a cross sectional area of 5 cm? and a mean diameter of 30 cm. An air gap of 0.5 mm is cut across the section of the ring. The magneto-motive force (mmf) produced by the winding on the ring is 500A-turns and it is found that the flux produced in the ring is 0.3 mWb. Find the relative permeability of the iron.
The typical behaviour of an individual motor is illustrated below. Give a clear explanation of the performance characteristics presented and the relationship between them. Identify the rated load and determine the amount of torque, speed, current and efficiency of the motor at that load.
) Explain how induction motors' speed can be controlled by frequency (for the below rated speed and above rated speed), include a sketch of the circuit configuration. The results of the no load and blocked rotor parameter tests on a 400 kW, 3300 V, three phase, 4 pole, 50 Hz, Y connected, squirrel cage induction motor is shown below: i. Calculate the no load core loss? ii. Calculate the equivalent circuit parameters in Ohms including R₁, R2, X₁ and X2 Assume that X₁ = X₂. iii.Provide a diagram of a single-phase equivalent circuit for this induction motor(referring to stator side), labelling the components clearly and indicated the supply voltage correctly. Considering the same induction motor as Q( 4b) and presuming the motor is operating at rated voltage and frequency, with a slip of 2.8 % and stator current value of l₁ = 68.01<-15.93° A, calculate the following parameters: i. Motor's Power factor? ii. Input power? iii. Stator losses?
To protect a house from electrical hazards, all household circuits should have a household electrical protecting circuit: mention one of them and explain how does it work?
Three single phase transformers are used to form a three phase transformer bank \text { - } 138 \mathrm{kV}(\Lambda) / 120 \mathrm{kV}(\mathrm{Y}) Source is a 120kV transmission line. ●Load side is a 12 MVA load at 0.8 Lagging PF. a. Turns ratio of each transformer. b. Line current at the 120 kV side.
Discuss the measures to mitigate EV load impacts by upgrading the distribution system infrastructure.
