Safety device
Page 75
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An earth leakage protection system with a breaker rating of 100amp and an unusually high trip speed of 25-28 milliseconds at 15 milliamps has been introduced by Winster Electronics Ltd. for use in all areas where electric current is used.
Although designed primarily for protection of human life against total electric shock, the device will also serve to safe guard electrical apparatus against damage due to electrical faults and to reduce possible fire hazards.
Contained in a neat sheetmetal weatherproof enclosure, the system may be mounted on a control circuit switchboard, wall mounted against an incoming supply for domestic and commercial applications, or attached to heavy portable equipment.
A design feature is that one trip unit can protect an unlimited number of points within the specified current rating, and while sensitive to faults in the area it is protecting it remains unaffected by faults on an adjacent circuit. Fluctuations in voltage supply and environ
mental conditions do not reduce performance.
The unit operates on the core balande principle, whereby currents in the load-carrying conductors are summed and, for a normal system, equate to zero. In the event of a leakage of current to earth, this balance is disturbed and an output is derived causing an electronic amplifier to actuate a relay. The relay contact is used to operate a shunt strip-coil on a circuit breaker or to isolate the operating coil on a contactor.
Efficiency of the unit may be tested as often as necessary by pressing a button which simulates an earth leakage fault and trips the circuit.
Two multi-voltage versions of the system are available, either having an N/O relay contact for shunt trip-coil operation or an N/C relay contact for contactor coil operation.
Made by: Winster Electronics Ltd., Ilkeston, Derbyshire.
Price: £37 10s.