The MAFS 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. 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.
The spheres are made of highly polished copper with tungsten sintered inserts to reduce burn-off and 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 sphere distance is automatically adjusted by the Haefely impulse generator controls GC 223 or GC 257.
The HV units are made of stacked capacitors with inserted damping resistances and built on fiberglass reinforced cylinders. The MAFS are equipped with toroid electrodes and the H base frame of welded steel profiles is equipped with swivel castors. Models are available up to 3600 kV rated impulse voltage.
DATA SHEET: MAFS Multiple Chopping Gaps