Development of the New PTB Highly Accurate AC Power Source

A highly accurate ac power source for unity power factor with an expected total uncertainty of a few parts in 10/sup 6/ to be used in the power frequency range is described. The rms value of the output voltage is continuously readjusted to a precisely known dc reference voltage using a multijunction thermal converter. A reference current is derived from the output voltage using an accurately known reiistor. The output current of a transconductance amplifier is compared to this reference current by means of a current comparator and continuously readjusted.