AC Power Pod
The AC Power Pod is installed on the SDC to convert the 230V AC power, transmitted via the umbilical from the Topside AC Power Cabinets, into DC power supplies for SDC equipment and variable intensity bell external light signals.
Each AC Power Pod has a triple output DC Power Supply. This power supply provides a 25V DC supply at 25A used for SDC 24V DC equipment and two variable voltage (3V to 31V) supplies used for the diver hat-lights. These supplies are powered from the 230V ‘Instruments’ supply, fed from the topside AC Power Cabinet. The 25V power supply output is protected by a 25A output circuit breaker which is fitted with a motorised actuator, allowing remote operation (open or close) under command from the iBIS Server.
A separate 230V AC power supply is fed to each AC Power Pod for the bell external lights. This External Lights' supply passes through 4 separate lamp dimmer circuits, each with its own 5A motorised circuit breaker (remotely operable from the iBIS Server). This arrangement allows each AC Power Pod to control power to four independent 230V 800W AC lights. Double-pole relays switch these supplies, and separate power cables are used for each light.
The construction of the AC Power Pods is similar to the SDC Mux Pod, in that the pod is a 1-atmosphere stainless steel unit with a connector end-cap and a removable cover. Again, these pods are fitted with a vacuum valve and sensor to allow pre-dive seal checking. Note – the AC pods are not normally operated with partial vacuum inside – as this reduces the thermal cooling of the pod. Rather, the pod seals are checked with the vacuum system, and then the vacuum is released prior to diving.
The AC Power Pods include a sophisticated diagnostics system, providing instrumentation of input and output voltages, output currents and water ingress detection. There is also a DC Line Insulation Monitor (LIM) which continuously monitors the quality of the insulation between the system’s DC power supplies and earth. This LIM does not shut down anything in the event of a fault, but provides operators with a warning of DC circuit insulation problems.
The MKII AC Power Pod, as being supplied to the Seven Kestrel and Deep Explorer, incorporates an outer jacket allowing a water-fill feature. This cooling arrangement allows for the SDC to be under power in the hangar area for a longer period of time.