USNS OBSERVATION ISLAND
The drive, a Siemens SIMOREG 6RA70 DC Master Variable Speed DC Drive retrofitted in their existing space on the USNS Observation Island which is one of 24 Military Sealift Command ships in the Special Mission Ships Program.
The drive is rated per information and discussions made available for the Bow Thruster retrofit application. Because or the available line voltage of 720 VAC we recommended a 690 VAC input Siemens DC drive PN/6RA7093-4KV62-0Z+X01. The drive is built to a compact footprint made especially for retrofit jobs. Dimensions of this unit are 35”X18”X20”.
Drive Requirements for the following needs:
- 720 VAC line input. Drive rating max. 690 VAC +10% (No need to change existing Isolation transformer)
- Armature rated output of 1094 ADC/750 VDC. Drive rating max. 1500 ADC/725 VDC but with higher input voltage 800 VDC can be achieved.
- Shunt Field output of 240 VDC/17.6 ADC. Drive rating max. 375 VDC/40 ADC. Needs separate 480 VAC/1 phase supply and fusing.
- 4-20 ma input used for phasing back DC drive during power limit application. Parameter set-up by customer.
- Drive blower assembly included needs separate 480 VAC/3 phase supply and starter for overload protection.
- SCR (Silicon Controlled Rectifier) line fusing.
- Standard CUD1 onboard electronics board.
- Standard PMU operator panel for programming and display
- Drive electronics will need separate 480 VAC/1 phase power, fusing internal to drive.
- Complete set of operation manuals.
- DC isolation contactors Not incuded.
- Exciting Input AC line reactors may be reused but we do not recommend reusing the DC armature or field reactors with this new drive.
Wire check of Siemens drive after retrofit, programming of the drive, self-tuning run of the DC motor, and Set-up the ship personal laptop computer with Drive Monitor software program. Detailed description and set-up sheet was provided to aid in the operations manual and for sea trial commissioning.
Joliet Technologies also provided a Harmonic Guard for the ship bow thruster DC drive application.
The HARMONICGUARD™ DRIVE-APPLIED HARMONIC TRAP FILTER (hereafter called a “trap filter”) contains tuned circuits designed to remove harmonics generated within a power distribution system while improving the system power factor. Unlike standard power factor correction capacitors, trap filters minimize the possibility of system problems associated with power factor correction in the presence of harmonic distortion.
Trap filters consist of inductive and capacitive elements arranged in a series configuration and are tuned to resonate just below the harmonic frequency for which they are designed to filter. The trap filter has its minimum impedance at the tuning frequency and, therefore, serves as a “sink” for harmonic distortion. At frequencies above the tuning frequency, the trap filter’s impedance is inductive; therefore, it cannot adversely react with the parasitic inductance of the power system. The inductance in the trap filter, combined with the series line reactor, acts to limit current surges between the capacitor and other plant electrical equipment. Again, this minimizes the possibility of equipment or capacitor damage due to such surges.
The trap filter described in this specification was used on a 450V, 3-phase, 60Hz system. The trap filter was rated 480V, 3-phase, 60Hz, 400 KVAR and was to be tuned to 4.7 times the fundamental frequency. The trap filter is UL-listed.
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