|C o m m e r c i a l
M a r i n e A p p l i c a t i o n s
STO-P was originally designed for the demanding marine environment where electronics and navigation equipment is essential for safety at sea. Nowhere else are the problems of power reliability so important. As we pointed out in the 'Common Electrical System Faults' section (see sidebar menu), high voltage faults damage electronic components making them more susceptable to environmental stresses. The more they are exposed to high voltage faults, the more likely they are to fail - the effect is cumulative.
For example, marine radar often fails when it is needed the most - in the midst of a thick fog, or when approaching an unfamiliar port at night. There's a logical explanation for this. In low visibility situations, radars operate for long periods of time. Continuous use generates heat within the equipment. Heat stresses components which have already been weakened by exposure to electrical system faults. A component fails and the radar ceases to operate - at the worst possible time.
Many marine operators are aware that engine cranking causes high voltage spikes as the solenoid and starter motor engages and disengages. But, there are many other sources of high voltage spikes and faults as the diagram below shows:
HIGH VOLTAGE WORRIES:
Transients of several hundred volts peak-to-peak can be measured using a high speed digital oscilloscope at various points in the electical distribution system. See the sections on transients, spikes and surges for details.
Lightning is another hazard. A direct hit is quite rare if you remain near land, or are berthed in a marina or port. But, nearby hits (within 1 KM or so) to buildings, radio towers, etc. can induce large voltages (i.e.m.f.) in boat wiring where it is distributed to equipment.
RADIO 'RF 'INTERFERENCE: (EMI)
Electro-magnetic interference from high powered SSB radios pose another problem for many types of electronic equipment. Boat wiring acts like an antenna. Power leads, which are rarely shielded, can pick up large induced voltages as their length approachs resonance at the operating frequency. Autopilots wander off course, GPS waypoints are scrambled, NAVTEX stops working, and instruments give wild readings. The effects vary according to transmitting frequency. It may be terrible at 4 Mhz and non-existent at 12 MHz, or vice versa. Each installation is different because of such variables as power lead length and the peculiarities of the radio installation.
BATTERY CHARGER PROBLEMS:
Using a battery charger when at the dock is a necessity for most vessels but it causes problems. AC mains surges due to the operation of heavy equipment in port, and by distant lightning strikes, are coupled onto the ship's DC power system. A look at our section on 'Surges' shows that voltage spikes of a thousand volts, or more, are frequent even in 'low risk' areas.
Many of today's high tech battery chargers use a pulse charging technique which generates substantial amounts of Ripple which can be heard as a buzz or whistle in audio entertainment and communications equipment. The 'theory' is that the battery bank will act as a filter. In the real world, ripple can be substantial and it affects equipment. While unlikely to damage equipment outright, it does produce annoying 'hum' and 'noise' on audio equipment and is often heard on VHF radios. At the very least, it sounds very 'un-professional'.
WHAT STO-P UPS DOES:
The key to reliable marine electronics is to keep electrical fault OUT! Installing STO-P in-line on power leads accomplishes this. High voltages are sensed and treated the instant they exceed the 'safe' level. STO-P's response time is typically 1 nanosecond (one billionth of a second) or less!
The STO-P UPS series is designed to maximize suppression of EMI and Ripple by presenting a very low impedence to ground at frequencies above a few Hz. For example, The typical output impedence at 120Hz is 0.03 ohm, falling to 0.02 ohm at 1KHz. Ripple and EMI are reduced significantly. In some cases, this low impedence will also improve the overall audio quality of brand new communications radios.