The multiple chopping gap is a patented Haefely design and is used to chop lightning impulses (on the front and on the tail) as well as switching impulses up to the highest voltages.

The multiple chopping gap serves simultaneously as a load capacitor for the impulse generator and allows excellent reproducibility of the chopping time and does not distort the wave shape until the chopping point.

With an additional secondary unit, the MAFS can be used, in some applications, as a voltage divider.

Rod gaps and sphere gaps (above 1000 kV) draw a substantial pre-discharge current prior to the voltage break-down, causing a voltage drop. This affects the comparison tests when testing power transformers, hence particular attention must be paid to the way the circuit is built.

The sphere distance is automatically adjusted by the Haefely Impulse Generator controls GC 223, GC 257 & HVC 300 (Fiber Optic Connection).

In the automatic mode, the gap distance is set automatically as a function of the charging voltage. The gap distance is displayed on the controls. The chopping is initiated by the first stage, having a triggering spark plug.

A manual control box GSC 219 is available to adjust the gap distance standalone or with non-Haefely control systems

The HV units are made of stacked capacitors with inserted damping resistances. This active part is built on reinforced fibre-glass cylinders.

Our active part technology is derived from our decades-long experience. The copper spheres have tungsten sintered inserts to reduce burn-off. Their distance is set by a precise drive. The upper semi-sphere is attached to a movable frame which makes it possible to adjust simultaneously all spark gaps.

The multiple chopping gaps are equipped with toroid electrodes. The electrodes are made of brushed aluminium. The electrode type is determined by the rated voltage. Fibre-glass struts are required when more than 2400 kV rated MAFS is used. The H base frame of welded steel profiles is equipped with four swivel castors.