Page 139 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

FIGURE 6.5
Sub-Atlantic Model SA300 hydraulic (a) and SPE-250 electric (b) thrusters.
6.1 Propulsion and thrust 127
(a) (b)
The most critical of these components will be discussed in more detail in the following sections.
Power source
As more fully explained in Chapter 7, with a surface-powered ROV system, power arrives to the vehicle from a surface power source. The surface power can be in any form from basic shore power (e.g., 110 VAC 1Φ 60 Hz or 220 VAC 1Φ 50 Hz—which is standard for most consumer electrical power delivery worldwide) to 480 VAC 3Φ (50 or 60 Hz) to a DC battery source.
For an observation-class ROV system running on DC power at the vehicle, the AC source is first rectified to DC (either on the surface or at first arrival at the vehicle) and then sent to the submersible’s components for distribution to the thrusters. The driver and distribution sys- tem location will vary between manufacturers and may be anywhere from on the surface con- trol station, within the electronics bottle of the submersible, to within the actual thruster unit. The purpose of this power source is the delivery of sufficient power to drive the thruster through its work task.
For the mid-sized and work-class ROVs (MSROV and WCROV), power is converted/condi- tioned at the surface to a form appropriate for the length of umbilical/tether (typically 3000 VAC or greater) and then sent to the vehicle. Typically, the vehicle manufacturer decides upon the depth capability and designs the vehicle electrical system to conform to the tether length. Most vehicle sensors operate on low-voltage DC power; therefore, a rectifier must be in the circuit somewhere. Deepwater ROVs (MSROV or WCROV) run high-voltage AC power down the umbilical to the TMS. Most MSROVs have a step-down transformer at the TMS that then powers the components of the TMS and ROV at lower voltage. Some electrical thrusters are designed to operate on AC power while others operate on DC (which determines the location of the rectifier). From there, mul- tiple power circuits are powered depending upon the needs of the components. The thruster circuit is typically on a separate circuit compliant with the needs of the electric thrusters. On the hydraulic vehicles, it is simply the lights, sensors/electronics, and the pump.
(Courtesy Forum Subsea Technologies.)