As noted previously, approximately 60 horsepower (electric) must 

 be provided at the surface to supply the required 28.6 horsepower at 

 the kelly drive motors. Electric power would be generated at 440 volts 

 and transmitted over the E-M cable at 2300 volts. A submerged stepdown 

 transformer would provide the power at the appropriate voltages for the 

 pump motor and the control and feedback functions . 



The electric motor would be located within the hydraulic fluid 

 reservoir, similar to the NCEL seafloor deep corer design. The design 

 is a standard modification of an industrial three-phase motor. 



Control and Feedback Subsystem 



The control and feedback subsystem includes the controls and feed- 

 back instrumentation of all submerged and surface equipment. The sub- 

 system presents the greatest potential for simplification and cost re- 

 duction by judicious choice of the required control and feedback func- 

 tions and the balance of automatic and operator control. The preliminary 

 design presented herein is probably not optimum but is a good basis for 

 the final design. The major effort required is the analysis of the sub- 

 system for the most cost-effective balance of automatic and operator 

 control. The goal is to minimize or eliminate the need for multiplexing 

 of control or feedback signals on the E-M cable. 



The preliminary functional design of the control and feedback sub- 

 system is shown in Figure 12. Control fiinctions are shown as dashed 

 lines and feedback functions as dotted lines. A total of four control 

 channels and nine feedback channels are required for the envisioned 

 system. Each channel is simply an on/off channel; no proportional con- 

 trols or feedback are needed. 



The four control channels are utilized to operate solenoid-controlled 

 hydraulic spool valves — one for each of the three hydraulic motors, and 

 one for a bypass valve (Figure 11). Each of these valves requires a 

 feedback channel to verify its operation. 



A fifth hydraulic valve operates the Installation unit release 

 mechanism as described above (Installation Subsystem). It is controlled 

 by the pile travel limit switches — when all three piles have reached 

 maximum travel and have tripped limit switches the installation unit 

 release is automatically activated. 



The pile travel limit switches are also connected to the motor 

 valves. As each pile reaches its maximum travel the limit switch closes 

 the corresponding motor valve and opens the bypass valve. This prevents 

 the rotation of the pile after it reaches full depth and minimizes soil 

 remolding. The feedback channels for the motor valves thus function as 

 the feedback for the pile travel limit switches. 



