Patent ID: 7187569
Filing Date: 2007-03-06
Classification: G01V,H02M

Abstract:
1. A cycloconverter for subsea electromagnetic exploration, comprising: a transformer having a primary side for receiving a high voltage low current signal of a first frequency and a secondary side for outputting a low voltage high current signal also of the first frequency; a switching circuit connected to receive the low voltage high current signal from the secondary side of the transformer and to switch its polarity so as to generate an output signal having a significant component at a second frequency lower than the first frequency; a controller configured to control the switching circuit responsive to a measurement of the first frequency; and a zero-crossing detector for measuring zero crossings at the first frequency and supplying a zero-crossing signal to the controller, the controller being configured to supply a switching signal to the switching circuit when a zero-crossing signal is received during a time window that has been determined by the controller responsive to the measurement of the first frequency.