Which of the following statements regarding the wind turbine gearbox are true? Select one or more: O a. After the gearbox, the rotational speed of the shaft is slower than the rotational speed of the turbine rotor (= blades). b. There are typically one planetary gear + 2 helical stages O c. With a single planetary stage, a 1: 6 gear ratio can be achieved. Od. The gearbox is usually 4-speed

G-1). The 3-phase squirrel-cage induction motor has a poorer starting torque than might be expected based on the line current being drawn, because the rotor current and stator currents are out of phase as a result of the high rotor frequency at starting. a) true b) false G-2). Which of the following is/are a general method of starting squirrel-cage motors? a) full voltage starting b) reduced voltage starting c) both  a" and "b" d) neither "a" nor 'lb" G-3). What is, if any, an objection to building a 3-phase squirrel-cage induction motor with high enough rotor resistance to provide good starting torque? a) stator current would increase b) speed regulation would get poorer c) rotor current would increase d) none of the above G-4). Which code letter(s) is given to the rotor of a 3-phase squirrel cage induction motor with the highest resistive value? a) A  b) B-E  c) F-V  d) none of the above

A/ A460 V, 25 HP, 60 Hz, 4 pole, X-coun- IM. Find' The useful torque and motor efficiency at rated Slip of 2.2% if the total motor impedance at Thise slip is 14/33.6°52 and total rotational losses are loow (R₁ = 0.64-52). B/ Explain the effect of voter resistance of motor output forque.

The following figure shows the circuit of a DC drive system. Choose the right expression concerning this system. Forward bridge Reverse bridge L1 L1 L2 L3 23 Armature Shunt field L3 23 L2 O a. This drive is a Regenerative DC drive. It allows controlling the motor speed ONLY below its base speed. Changing the rotation direction requires to feed the motor from the reverse bridge. The reverse bridge is also used while braking to transform the excess energy into AC and feed it to grid lines O b. This drive is a Non-regenerative DC drive. It allows controlling the motor speed below and above its base speed. Changing the rotation direction requires external contactors to be connected. The reverse bridge is used while braking to direct the excess energy to braking resistor bank Oc. None of the choices Od. This drive is a Regenerative DC drive. It allows controlling the motor speed below and above its base speed. Changing the rotation direction requires to change the pulses fed into the…