Method and apparatus for testing electrical equipent
AssigneeERA Patents Limited
InventorRaymond L. Coleman
Life of this patent
Estimating the term…
Abstract
In a method of testing electrical equipment having inherent stray impedances while the equipment is connected to a conductor a swept sinusoidal signal is injected and the response of the equipment to the signal analysed. In order to prevent current flow within the conductor affecting the results of the analysis a nulling signal is injected to nullify the current which would otherwise flow in the conductor as a result of the application of the swept-frequency signal. In a preferred embodiment the phase and amplitude of currents in the conductor and in the line through which nulling signals are injected are compared. The phase and amplitude of the nulling signal are adjusted in accordance with the result of these comparisons.
Claims10
An apparatus for testing an electrical system comprising electrical equipment having inherent stray impedances and conductor means connected to said equipment, said apparatus testing said electric system by detecting values of said inherent stray impedances in said equipment which are indicative of the state of said equipment, said apparatus comprising:
- probe signal applying means arranged to be operatively connected to said conductor means adjacent said equipment and to apply a probe signal of substantially sinusoidal waveform;
- frequency sweeping means operatively connected to said probe signal applying means to sweep said probe signal over a predetermined frequency range;
- current monitoring means arranged to be operatively coupled with said conductor means remote from said equipment to monitor current flowing in said conductor means as a result of said application of said probe signal;
- nulling signal feed means arranged to be operatively connected to said conductor means remote from said equipment to feed a nulling signal to said conductor means to nullify said current flowing in said conductor means;
- and,
- analyser means arranged to be operatively connected to said conductor means adjacent said equipment to analyse a response of said equipment to said probe signal to determine frequencies at which specific responses are produced as the result of said values of said stray impedances of said equipment whereby effects of impedance of said conductor means are eliminated.
A method of testing an electrical system comprising electrical equipment having inherent stray impedances and conductor means connected to said equipment, said method detecting values of said inherent stray impedances in said equipment which are indicative of the state of said equipment, said method comprising the steps of:
- applying to said conductor means adjacent said equipment a probe signal of substantially sinusoidal waveform;
- sweeping said probe signal over a predetermined frequency range;
- feeding to said conductor means remote from said equipment a nulling signal arranged to nullify a current flowing in said conductor as a result of applying said probe signal and thereby eliminating effects of impedance of said conductor means;
- analysing a response of said equipment to said probe signal by determining frequencies at which specific responses are produced as a result of said values of said stray impedances;
- and,
- comparing results of said analysis with expected values of said stray impedances of said equipment thereby determining said state of said equipment.
Dependencies are inferred from the claim text.