DEVICE FOR TESTING THE ADEQUACY OF ELECTRIC TOOLS, EXTENSION CORDS AND THE LIKE INCLUDING ENERGIZATION REMOVAL MEANS TO REDUCE HEATING

摘要

Device for testing the adequacy of the ground and power circuits of electric tools, extension cords and the like by performing an automated series of individual tests in sequence. The major tests are to determine: open ground circuit, faulty ground circuit, short circuit and poor insulation. If no faults are found by these tests, the circuit under test is next connected to line potential to determine if it operates properly. During this phase of testing, the potentials and currents associated with the previous tests are discontinued to avoid power drain and heating. A saturating current transformer protects an essential relay from damage from excessive current. A long extension cord having a proper ground resistance (in the order of the resistance exhibited by a tool having a faulty ground cord) may be tested by modifying the test currents so that an erroneous faulty ground indication is not given.