Technical Information

Capacitive Load (capacitors, cable)

The capacitive load has a current waveform which is LEADING the voltage waveform, voltage peaks and current peaks are not in-phase. The amount of phase delay is given by the cosine of the angle (Cos) between the vectors representing voltage and current.

The relation is:

Watts (w) = Volts (V) x Amps (I) x P.F. (single phase)

Watts (w) = v3 x V x I P.F. (Three phase)
P.F. = (Cos) = Watts ÷ Volts x Amps
W KW
----- or -----
VA kVA

Frequency

Frequency (Hz) is measured in Hertz (cycles per second), this is the number of times that an AC supply oscillates in one second. The standard frequency in the UK is 50Hz and 60Hz in the US. However, bear in mind that if you are required to supply equipment offshore or on board ships, the frequency is usually 60Hz.

The frequency generated by an alternator is dependent on the number of poles in the alternator and the speed of the engine. The more poles in the alternator the slower the engine speed. A standard machine has 4 poles.

Relationship between speed and number of poles.

Engine Speed (Rpm)	Number of Poles	Frequency (Hz)
3000	2	50
1500	4	50
1000	6	50
750	8	59

The engine speed of a standard DeciBeater is 1500rpm for 50Hz and 1800rpm for 60Hz. Speed is directly proportional to frequency, therefore it is extremely important that the correct frequency is applied to its application.

Technical Info