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Phase reversal of induced emf

  1. Mar 10, 2010 #1
    I want to know the physics behind the concept given below.
    A Transmitter coil(TX) is excited with an AC signal of frequency X KHz, V voltage, and N1 turns. A receiver coil (RX) with N2 turns is placed oppositely and a steel rail is placed in between. Under these circumstances a voltage Vr with a Frequency X KHz and in-phase to TX, shall be induced in the RX coil.
    case 2) When a wheel made of steel is rolled over the rail, and is at the proximity of coils, the induced voltage in RX shall fall to ZERO.
    case3) When a wheel made of steel exacltly at the center of coils, the induced voltage shall be vr, frequency - X KHz but Out-Of -Phase with TX signal.

    TX and RX coils can be termed as sensor, which detects a passing wheel on the rail based on the phase reversal principle.

    Please let me know the
    1) sequence of changes in the magnetic flux from the TX coil.
    2) As the wheel is a conductor whether magnetic flux couples the RX coil or not, under the presence of wheel?
    3) Whether the eddy currents in the wheel are responsible for the above said phenomenon for induction of voltage in RX coil, under the presence of wheel.

    Thanks in advance, and awaiting an appropriate reply.

  2. jcsd
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