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15 May, 2000kolb journal 05/15/00 Central Power Plant DRAFT May 15, 2000 Daily Data (20:30): Lat. 6400.075N Long. 06137.929W Heading 131.955 deg Air Temp. -4.60C 23.72F True Wind Dir. 065 deg True Wind Speed 10 knots (Note: The heading is the direction the bow of the ship is pointing at any instant instant expressed in degrees from 000 degrees through 360 degrees. Course is the intended direction of the ship and at a specified time may or may not coincide with the heading.) USCGC Healy Facts: Science Systems Winches-Two oceanographic winches, capable of handling 10,000 m of 3/8" wire, 12,000 m of 0.322" electro-mechanical cable, or 14,000 m of 1/4" wire. Two double drum trawl/core winches, capable of handling 10,000 m of 3/4", 12,000 m of 0.680" electro-mechanical cable, or14,000 m of 9/16" wire. Dear Everyone, Yesterday the helicopter reconnaissance flights were unable to locate a suitable ice floe of level compact 125 cm ice for further. Although the ice trials data are more than adequate, this additional information would have been the "icing on the cake". The day, however, ended quite successfully with the Healy completing two turning radius tests in two thicknesses of difficult ridged first-year ice. As in the start-up trials, the turning radius tests were executed in ice 75 cm and 135 cm thick. This resulted in good data collections and happy scientists. The Healy is steaming south. This morning, after our night of travel, the ice has changed considerably. The expansive first-floes and rubble fields are now to our north. We are smoothly traversing through pancake and brash ice. Within a few hours the Healy will be in open waters. What powers the Healy? What is the propulsion system and how does it function? The generating plant? The drive With these questions in mind, Lt. Troy Kunas, Assistant Engineering Officer, responsible for the Healy's central and power plant, provided me with an overview of these systems. The USCGC Healy is the only United States flagged vessel with an integrated power plant. A common generated power source the central power plant, supports both the propulsion and the hotel services (i.e. lights, food services equipment, power for computers, lamps, small equipment and appliances) of the ship. The power is provided through a 6600VAC, 60Hz, 3-phase common bus system and is generated by four diesel generator sets rated at 7.2 megawatts located on the main deck. If all four generators would be operating, 29 million watts of power could be generated. The common bus has circuit breakers that can split the bus, but normally it remains closed. Additional safety practices not normally a part of ship standards are necessary on the Healy due to the exceedingly high voltages on board. A 16-foot danger area surrounds the 6600-volt vicinity. A plasma blast can occur in the air when an electrical arch passes through it. This could be compared to lightening. The closer a person is to the voltage source, the greater the safety risk. Protective clothing called "Kevlar Flash" gear must be worn and strict safety standards observed. To supply the Healy's hotel services at the proper voltages, transformers and motor generator sets (MG sets) are used. One of the two transformers reduces the 6600 volts to 450 volts and provides power to the larger sensitive pieces of equipment. The has two MG sets that power the smaller more sensitive equipment. Total harmonic distortion (THD) is a measure of the true departure from a true voltage sine wave. This is an indication of power. Large machinery continues to function successfully when THD is present, but sensitive hotel service equipment (i.e. computers, small machinery, fluorescent lamps, ship radar equipment) is very sensitive to harmonic distortion. A way to maneuver around total harmonic distortion (THD) as a problem is to use motor generator sets (MG sets). The generator side is mechanically coupled to the generator, not electronically coupled. This results in the noise being removed from the sine wave. Consequently, 'clean' power comes from such a coupled generator. The 'sensitive bus' supplies the Healy's wall outlets for the equipment and appliances (especially electronics equipment) sensitive to harmonics. The 'non-sensitive bus' feeds the Healy's large motors and all equipment not affected by harmonics. Why does the Healy have total harmonic distortion (THD)? The reason why THD is an issue is because the Healy cycloconverters. Cycloconverters put noise onto the bus as a byproduct of their operation. The Healy's auxiliary diesel generator (ADG) is rated at 2.2 megawatts and has the capability of carrying both the sensitive (Ship Sensitive) and non-sensitive bus (Ship Non-Sensitive) as well as the emergency bus (Ship Auxiliary). Normally the and SA buses are fed from a motor generator set (MG set). When the ship goes to 'hove-to' (i.e. anchor or in port without shore power available) not all the power of the main diesel system is required. At this point, the auxiliary diesel generator (ADG) will be started and supply all three buses and the main diesel will be secured (turned off). Lt. Kunas continued our conversation by discussing the Healy's propulsion systems. This power is supplied by two AC synchronous motors that are variable speed and fully reversible. The motors are fed from the common bus through an AC/AC Cycloconverter system. What do the cycloconverters control? They control the speed of the propulsion motors through varying the frequency of power provided to the motors. How is this done? By taking two 3-phase schemes and converting them to one 6-phase device and then performing full-wave rectification, it will provide a 12-plus-power supply to the motor. The device that is used for the rectification is called a thyrister. This could be described as a diode having a gate (a current or voltage signal to the junction). In order to control the flow of current through the diode, the gate is used to open and close the diode. The cycloconverter controls the turning on and off of each of the thyristers. By controlling this, the amount of power going the main motor can be monitored and the wave flow going to it can be changed. The frequency of the pulse directed to the main motor is 0-20 Hz. Because the motor is synchronous, manipulating the frequency going to it can control the speed of the motor. When the voltage comes out of the cycloconverter, it is 2380 volts. A key part of the operation is the phase shift in one set of the transformers to give a 6-phase power supply to the motors. One of the cycloconverter drive transformers is a Delta/Y configuration and the other one is a Delta/Delta configuration for each shaft. Basically this provides two 3-phase power supplies that are 60 degrees out of phase of each other. This, in essence, provides the ability to have a 6-phase power supply to the main motor. The 6-phase power supply when full wave rectified provides more power, more control, and a smoother operation of the main motor. More photos have been added to my previous journals. Data on ice core 4A of April 11, 2000 follows. Best regards, Sandra Kolb Core 4A level ice 0411, Beginning of Start-Up Test 11-April-00 Total length 66 cm Longitude 62 deg 09.6713 min Comments: air temp -10.07 C, beginning of test Brine volume for -2>T>-22.9 Brine volume coefficients: F1(T) COEF. -4.732 -22.450 -0.640 -0.011 F2(T) COEF. 8.90E-02 -0.018 -0.001 0.000
average brine vol 0.0796 average strength mpa 0.335 average strength psi 48.6 -- April M. Metz Web Designer/Coordinator Department of Earth Sciences Rice University Weiss Geology Building, Rm 318 ametz@esci.rice.edu 713-348-2356
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