A high efficiency motor is connected to a shaft reducer. If the efficiency of the motor is 87.5% and that of the shaft is 95%, what is the efficiency of the system? If this system is connected to a helical bevel gearbox with efficiency of 77.5%, what is the overall efficiency of the combined elements.

A 2-pole wound rotor three-phase asynchronous motor is connected to a three-phase 380 V compound voltage network. The stator and rotor are star connected. The transformation ratio of voltages coincides with that of currents and is equal to 2.5. The parameters of the equivalent circuit of the motor per phase are: R1 = 0.5 [Ohm], X1 = 1.5 [Ohm], R2 = 0.625 [Ohm], X2 = 1.25 [Ohm], RFE = 360 [Ohm], XM = 40 [ Ohm]. The mechanical losses are 250 [W]. If the slip at full load is 5 [%], it is ordered using the approximate equivalent circuit of the motor: a) Stator current, rotor current, magnetizing current. b) Loss of iron, active and reactive power absorbed by the network motor. c) Internal power and mechanical power in the shaft.

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The armature of a shunt generator has 0.08-ohm effective resistance. Each brush has an effective resistance of 0.02 ohm. The terminal voltage is 120 V while the current is 60 A. What is its efficiency?

3. Two 750 kW alternators operate in parallel. The speed regulation of one machine is 100% to 103 % from full-load to no-load and that of the other is 100% to 104 %. How will the two alternators share a load of 1000 kW ? [464-3 kW; 535-7 kW]

Six generators are operating in parallel supply a total current of 3500 A. Each machine has a field resistance of 60 ohms and an armature resistance of 0.01 ohm. The emfs generated of these generators are 250, 270 ,280, 290, 300, 310 volts respectively. Find the share of each of the generator.

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Choose the right answer. 1. The basic elements in any power system are 2. The reactors have the following problems 3. If a fault occurred between phases (A, B, and C) simultaneously the fault is called if the fault occurred on phase (A) only or phases (A, B), it may take the following types and ...... where or 4. The symmetrical component method is 5. Conditions for succesful operation of a power system are 6. The reason we use the numerical methods in load flow analysis is 7. The main diagonal of Y-bus numbers by a factor / not any) 8. The properties of the fault currents and (changes the signs / keeps the signs / multiplies the .... .... ....... re

Refer to Image. Suppose we apply 160 volts AC to 80 turns of the primary winding but the secondary winding only has 25 turns. What is the turns ratio in this system?   Please draw images