Instrumentation

    TCL manufacture a number of instrumentation products specifically designed for turbine applications:

    Speed Module


    Speed Conditioning Module

    Magnetic speed pickups are typically installed to measure the speed of a turbine. The output of these probes is a sine wave whose amplitude varies with the speed of the turbine shaft. This signal can be difficult to read using digital counter modules for the following reasons:

    • The amplitude is low at low speed and might not reach the trigger level of the module. This is particularly critical for measurement at turbine barring speeds.
    • The amplitude may be very high at high speeds which may exceed the maximum input voltage level of the module.
    • The signal may suffer from electromagnetic interference, causing a fluctuating speed reading.
    • The wavelength of the signal may change due to mechanical dimensional inconsistencies, e.g. gear teeth inaccuracies.

    The two channel speed input module has been designed to produce a square wave output signal of constant amplitude regardless of input signal. The input filtering reduces noise interference with an option of phase lock loop (PLL) circuit to ignore high-frequency interference.

    Tacho-Gen Replacement


    Tacho-Generator assembly

    Speed pick-up assembly

    Tacho-generators where fitted to many older gas generators such as RR Avon and Olympus engines to measure shaft speed. These devices are three phase generators that produce a low-frequency low voltage output. This signal can be difficult to read using digital counter modules for the following reasons:

    • The low frequency causes resolution problems and inaccuracy in speed measurements.
    • The amplitude is low at low speed and might not reach the trigger level of the module. This is particularly critical for measurement at turbine barring speeds.
    • The signal is extremely susceptible to electromagnetic interference, causing a fluctuating speed reading.
    • The connectors of these devices have proved extremely unreliable and the electrical connections break down in the harsh industrial environment of a Power Station.

    We produce a replacement device that utilises a phonic wheel and magnetic pick-up (MPU). This picks up the same drive as the existing tacho-gen, but the phonic wheel and MPU produces a higher frequency and amplitude AC output.