Silicon controlled rectifier control of sub-sea towed electromagnetic source

摘要

A method and apparatus for generating an electromagnetic (EM) field from a sub-sea source is disclosed. In one embodiment, a sub-sea source includes a step-down transformer coupled to receive a sinusoidal source wave via a tow cable, and is further coupled to output a sinusoidal wave to a silicon-controlled rectifier (SCR) circuit. A control circuit coupled to the SCR circuit is configured to selectively activate various ones of the SCRs therein in order to control a portion of the sinusoidal wave that is rectified. The output current provided by the SCR is determined by the portion of the sinusoidal wave that is rectified thereby. The output current is provided to electrodes coupled to the sub-sea source, and the output current is passed therebetween. The strength of the EM field is based on the output current.

主权项

1. An apparatus comprising:
a sub-sea electromagnetic (EM) source configured to generate an EM field, wherein the sub-sea EM source includes:
a silicon controlled rectifier (SCR) circuit configured to rectify a selected portion of a sinusoidal wave to produce an output current used to generate the EM field;a control circuit configured to activate the SCR circuit at a time difference relative to a zero-crossing point of the sinusoidal wave, such that the selected portion subsequent to each zero-crossing is less than a half-sinusoidal portion of the sinusoidal wave and wherein the control circuit is further configured to vary the output current by varying an amount of the time difference between different activations of the SCR circuits for the sinusoidal wave; anda pair of electrodes configured to use the output current to generate the EM field.