Six hundred power transistors on water‐cooled heatsinks are connected in a Kerns actuator circuit to modulate the power line feeding the Berkeley 88‐Inch Cyclotron. The regulator senses the rectified three phase line voltage and attenuates the frequency components between 0.001 and 200 Hz to 0.03% of the average value. Elimination of these components from the main power line removes the need for expensive wide band regulators for each of the many critical high power loads in the building. The paper discusses the design considerations and construction techniques of this regulator.