Ferranti Subsea Systems, Inc.

Wayne D Crowe

A source of DC electrical power (A) provides DC electrical power to a power transmission cable (B) which extends to a remote location, such as a subsea module (D). The power transmission cable is connected with a pair of rectifiers (20a, 20b), each allowing only power of a selected polarity to be passed thereby. A pair of DC to AC inverters (24a, 24b) convert the received electrical power to high frequency square waves which are applied across primary windings (32a, 32b) of inductive couplers (30a, 30b). Secondary windings (38a, 38b) of the inductive couplers convey the AC electrical power to remote module rectifiers (40a, 40a) for providing DC electrical power to the subsea module. In this manner, DC electrical power is transmitted along the power transmission cable to reduce interference and crosstalk, yet the electric power is transmitted across an inductive coupler to facilitate safe separation of the remote module from the power transmission cable.

Power transfer of direct current with inductive couplings

A local data unit (10) provides sequenced acquisition and transmission of data signals received in different signal formats from local and remotely deployed sensors (24, 28). The network uses a microprocessor based stage (42) to sequentially control acquisition of the data signals via an analog multiplexer (16) and conversion of those data signals into a binary format via either a voltage-to-frequency converter (48) and frequency digitizer (58) or, after normalization, directly via the frequency digitizer (58). Data transmission in a normal mode is achieved by using the binary data signals to toggle input reference signals applied to multiplexer (16) between low and high potentials, and applying those potentials to voltage to frequency converter (48) while a data transmitter (52) is held in an enabled conditon. The tone of the resulting frequency shift keyed signal is sensed by a carrier detector (82) which in turn enables a master telemetry receiver (80) to receive the data signals after conversion by a decoder (84). In a fallback mode activated upon failure of the processing unit, the multiplexer is sequentially addressed to apply the incoming data signals to the voltage-to-frequency converter (48) while the data transmitter (52) is held in an enabled condition. After detecting the occurrence of the partial failure, the master processing unit shifts to alternate binary conversion modes to accommodate the formats of the directly transmitted data signals in accordance with the scanning sequence of the fallback mode scanner (74).

Multiple-mode data acquisition system

An exciter and detector circuit (A1, A2) is inductively coupled (18, 20) with a current conductor (B). The current conductor extends to a remote location at which it is inductively coupled (26, 30) with a remote transducer and encoder circuit (C1, C2). The exciter and decoder circuit supplies a square wave signal of a fixed frequency and amplitude across a primary winding (18) of the inductive coupler. After each half cycle of the square wave as the magnetic field in the inductive coupler is collapsing, a flyback voltage peak is generated which varies with the load applied to the current conductor. At the remote location, a voltage to frequency converter (40) converts variations in the output of the transducer into corresponding variations in a frequency signal. A load modulator (42) is connected with the voltage to frequency converter to apply a load to the rectifier at the frequency of the voltage to frequency converter. This causes the amplitude of the flyback voltage peaks to vary with an envelope frequency which is the same as the frequency of the voltage to frequency converter. A detector frequency to voltage converter (70) converts the envelope frequency into a voltage which varies in proportion to the envelope frequency, hence, to variations in the condition sensed by the transducer.

Remote, inductively coupled, transducer interface

A multiple-mode electrical power and communications interface includes a command encoder (10) modulating the frequency generated by a variable frequency power source (12) for transmission over one of two signal transmission paths (16/26) to a remotely located data acquisition and transmission network (32). The signal transmission paths (16/26) are connected via inductive couplers (20/24) to different directional control stages (50/52) which selectively enable corresponding frequency separators (54/62) for filtering the command component from the power component and applying the former to a command decoder (56). The direction control stages enable one of a pair of local transmitters (58/64) to send information encoded by a data encoder (60) over the other of the two signal transmission paths. A mode shifting transmit/receive switch (15) simultaneously and separately connects the two signal paths to the power source (12) and a data decoder (30). In the event of loss of one of the two signal paths, the mode shifting switch (15) can sequentially connect the power source (12) and data decoder (30) to the same signal transmission path.

Multiple-mode electrical power and communications interface

At a first location (A), a signal combiner (14) combines DC power from a DC power source (10) and command communication signals from a command encoder (12). An electrical cable (B) conveys the combined DC electrical power and command communication signals to a remote location (C). The command communication signals are read by a signal separator (32) and used to control a DC to AC converter (34) such that the DC to AC converter converts the DC power to a high frequency signal which is modulated in accordance with the command communication. The high frequency signal is transmitted across an inductive coupler (40) to the remote equipment. A command unit (50) separates the command communication signals from the high frequency signal to control switches (54) and the functioning of components (56) at the remote location. A rectifier (52) provides DC power to operate the controlled components. A pressure transducer (62) generates data communication signals which are transmitted uplink across the inductive coupler. The uplink data communication signals are read from the cable by a data signal separator (92) and converted by a decoder (94) to the appropriate electrical format for a man-readable display (96).

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Houston, TX, United States of America

Wayne D Crowe