Speed measurement / alarm




A generator is necessary in a coal-fired power plant to produce electricity.


A turbine-driven electrical generator contains a stationary stator and spinning rotor. In operation, it generates up to 21,000 amperes at 24,000 volts of three-phase alternating current (approx. 500 MW).


The rotor spins in a sealed chamber cooled with hydrogen gas. The system requires special handling during startup, with air in the chamber first displaced by carbon dioxide before filling with hydrogen. This ensures that a highly explosive hydrogen-oxygen environment is not created.


In this application, monitoring the speed of the rotor using a two-wire NAMUR sensor is very important to avoid over-speed. A solution for rotor over-speed protection is to use the PR 5725D programmable frequency indicator adding local readout and 2 relays for over-speed alarms and sensor error detection. The 4...20 mA output signal from the PR 5725 is connected directly to the control PLC.


What are frequency to current converters and what are they used for?






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