A heavily damped induction disc relay with an adjustable inverse time/voltage characteristic. The coil circuit of the relay is tuned to the supply frequency by a series connected choke and capacitor. These components are energized from a tapped auto-transformer which provides adjustment of the relay voltage setting. At voltages above the setting, the choke saturates and detunes the circuit giving the relay a high continous voltage rating. Damping of the disc movement is by a removable high retentivity permanent magnet.
The unique method of winding the operating coil ensures that the time/voltage characteristics are identical on each of the voltage taps. Selection of the required voltage setting is by means of a plug setting bridge which has a single insulated plug. Tuned wound shading coils are fitted so that the relay develops maximum torque at the supply frequency and is much less sensitive to voltage at third harmonic frequencies.
The relay operating time can be adjusted by movement of the disc backstop which is controlled by rotating a knurled moulded disc at the base of the graduated time multiplier scale Type VDG 14 relay is a single pole relay and is available in the single pole version only.