Frequency meters 11-1 measure cycles per rate of ac. The range of frequency meters found on gas turbine ships is between 55 hertz (Hz) and 65 Hz. Frequency of the ac used on ships rarely varies below 57 Hz and seldom exceeds 62 Hz. A frequency meter may have a transducer that converts the input frequency to an equivalent do output. The transducer is a static device that has two separately tuned series-resonant

Figure 11-18.-Frequency meter.

circuits, which feed a full-wave bridge rectifier. A change in frequency causes a change in the balance of the bridge. This causes a change in the do output voltage.

KILOWATT METERS

Matter is measured by computing values of current, voltage, and the power factor. The kilowatt meters (fig 11-19) used on ships automatically take these values into account when they are measuring kilowatts (kW) produced by a generator. Kilowatt meters are connected to both current and potential transformers so they can measure line current and voltage. Since each type of generator is rated differently, the scale is different on each class of ship.

The amount of power produced by a generator is measured in kilowatts. Therefore, when balancing the electrical load on two or more generators, you should make sure the kW is matched. Loss of the kW load is the first indication of a failing generator. For example, if two generators are in parallel, and one of the two units is failing, you should compare the Kw reading. Normally, the generator with the lowest kW would be

Figure 11-19.-Kilowatt meter.

the failing unit. There is one case, however, where this is not true. During an overspeed condition, both units increase in frequency, but the failing unit is the one with the higher load.