Construction of Moving-Iron Power Factor Meter

Construction of Moving-Iron Power Factor Meter Points : Construction of Moving-Iron Power Factor Meter One type of power factor meter suitable for 3-phase balanced circuits is shown. It consists of three fixed coils R, Y and B with axis mutually at 120° and intersecting on the centre line of the instrument, these coils are connected respectively in R, Y and B lines of the 3-phase supply through current transformers. When so energised, the three coils produce a synchronously rotating flux. There is a fixed coil B at the centre of three fixed coils and is connected in series with a high resistance across one of the pair of lines, say, across R and Y lines as shown. Coil B is threaded by the instrument spindle which carries an iron cylinder C to which are fixed sector-shaped iron vanes V₁ and V₂. The same spindle also carries damping vanes and pointer (not shown in fig.) but there are no control springs.