Calculate the current generated at rated power

Reference no: EM132893055

Question 1. This is a question about a wind turbine generator
a) The blades of a 20 kW, 400 V machine rotate at 2 revs per second at rated wind speed
i) Calculate the speed of the generator if the gear box ratio is 1:10
ii) Calculate the current generated at rated power
iii) This four-pole machine has a lap wound armature consisting of 16 coils each with a resistance of 0.3 ohms. Calculate the resistance of the armature.
iv) Draw the circuit diagram for the generator with this armature winding resistance and the shunt resistance is 50 ohms
v) Calculate the winding losses and hence the efficiency of the wind turbine at rated wind speed.
b) The actual wind speed is lower than rated, so that the blades rotate at half the speed. The output voltage is now 190 V
i) What is the induced emf at rated speed?
ii) What is the emf at actual speed
iii) What is the actual output current?
iv) What is the actual power generated?

Question 2. This question is about a d.c. compound wound machine acting as a motor
A 500 W, 200 V compound motor has two field windings, one has a resistance of 0.03? and the other a resistance of 50 ?
i) Draw and label a circuit diagram. Which winding should be connected to the Z-ZZ terminal?
ii) If the armature resistance is 0.15 ?, calculate the emf when it draws an armature current of 5A whilst running at 3000 rpm.
iii) When the load increases so that the motor draws a current of 10A, what is the new speed of the machine? (assume the field shunt current does not change - just the series field)

Question 3. This question is about transformer connection
a) Choose three different transformer protection devices. Give an advantage and a disadvantage of using each one.
b) Look at FIG 1, which is the heating curves for a 600 kVA transformer. Copy it and mark on it for your answer.
i) Identify the safe continuous temperature for this machine
ii) How long would it take for the transformer temperature to rise by 50°C if it were running at 750 kVA?
iii) If the ambient temperature were lower, what would happen to the time in?
iv) Draw on the diagram the time it would take for the machine to be at an unsafe temperature when pulling 750 kVA

Reference no: EM132893055

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