1. How could this be a generator??? 2. In 2nd picture, generator or motor and if

Question

1. How could this be a generator???

2. In 2nd picture, generator or motor
and if motion is clockwise is this a generator or motor

This fact can be used to produce an equivalent (and sometimes more useful) ex pression for the induced torque in the machine. From Equation (3-58) (3-58) But from Equation (3-59), B - e BR SO Since the cross product of any vector with itself is zero, this reduces to (3-60) so the induced torque can also be expressed as a cross product of B the same constant k as before. The magnitude of this expression is and e with (3-61) where 8 is the angle between BR and Bct Equations (3-58) to (3-61) l be used to help develop a qualitative un derstanding of the torque in ac machines. For example, look at the simple syn- chronous machine in Figure 3-19. Its magnetic fields are rotating in a counter- clockwise direction. What is the direction of the torque on the sbaft of the machine's rotor? By applying the right-hand rule to Equation (3-58) or (3-60), the induced torque is found to be clockwise, or opposite the direction of rotation of the rotor. Therefore, this machine must be acting as a generator. FIGURE 3-19 A simplified synchronous machine showing

Explanation / Answer

Further explanation: With respect to rotor, the stator conductors appear to be moving clockwise. Applying Fleming's Right Hand rule (to find the direction of current or EMF induced), the direction of currents induced in the stator will be as shown. The electromagnetic torque developed due to these currents tries to rotate the stator in the anti-clockwise direction. But the stator being stationary, the effect of this torque is opposition to the already rotating rotor, i.e., on the rotor, the induced torque acts in the clockwise direction. Thus, the given machine has to be a generator.

2. The 2nd picture seems to be no different from the first. So, it has to be a generator.

If the motion is clockwise, the machine has to be a motor, because the direction of the developed torque is same as that of the rotor rotation.

Further explanation: For the given current direction through the stator, the developed electromagnetic torque will try to rotate the stator in the anti-clockwise direction. This can be shown using Fleming's Left Hand rule. But the stator being stationary, the electromagnetic torque has a clockwise turning effect on the rotor. Since the motion is also given to be clockwise, the given machine has to be a motor.

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