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Electric
The UEP/ELFE Sweep
Capability
The sensors available to modern sea mines include electrodes and coils. With the help of on board microprocessor signal processing, these sensors are capable of reading a warship's static electric field or Underwater Electric Potential (UEP) and a warship's alternating electric and alternating magnetic fields by analysing the low frequency components of those fields (ELFE).
For example, electrode sweeps are rejected by modern mines equipped with UEP sensors due to the sweeps excessive UEP signature. Closed loop sweeps emit no UEP signature and are rejected by modern mines equipped with UEP sensors.
Ships operating in relatively shallow littoral waters are likely to encounter mines with impressive target selectivity, seeking to analyse and compare a target's combined magnetic, acoustic and UEP/ELFE signatures. To be accepted as a valid target by modern mines, a minesweeping system must be able to accurately emulate these signatures in shape, intensity and spatial relationship.
To answer the need to provide a Mine Warfare Commander with the option to include UEP/ELFE emulation in a multi influence sweep, The Australian Defence Science and Technology Organisation (DSTO) and ADI have developed a ‘clip on' UEP/ELFE sweep addition to the Australian Minesweeping System.
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Magnetic, Acoustic and Electric Multi Influence Sweep
The Towed Body Generator uses a turbine to power an on board electronic control module. The TBG delivers programmed power to the array electrodes to achieve the desired emulation.
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| The adjustable length, 8 electrode UEP/ELFE array is powered by the Towed Body Generator (TBG) | ||||
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Emulating a Warship's UEP Signature
A warship's static electric field or Underwater Electric Potential (UEP) is generated by a ship's passive or active cathodic protection systems. Emulation is achieved by providing programmable steady current to up to eight active electrodes along the sweep array in the same relative positions as the ship's emissions.
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| UEP/ELFE Sweep Electrode (Titanium) | ||||
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Emulating a Warship's ELFE Signature
A warship's alternating electric (AE) and alternating magnetic (AM) fields arise from sources such as a ship's AC power supply and corrosion current modulated at propeller shaft rotation frequency.
Emulation is achieved by providing programmable alternating current to at least two pairs of active electrodes along the sweep array in the same relative positions as the ship's emissions. Each electrode can output either DC current or AC current or both AC and DC simultaneously.
Recorded Results
The ELFE setting is programmed as a ship-like signature, producing both 60 Hz hotel electrical power-related frequencies (amidships) and 3Hz shaft-related frequencies in the vicinity of the stern. The fundamentals and their corresponding harmonic frequencies are shown below. The Shaft harmonic series is particularly prominent from 3 to 30Hz, and Hotel Power is shown at 60, 120, 180, and 240Hz. The following results were recorded by the Royal Australian Navy's signature analysis range;
Programmable ELFE Input
- Yellow Trace: ELFE (Hotel Power) on electrodes 3 and 4 at 60 Hz @1A, square wave.
- Blue Trace: ELFE (Shaft Frequencies) on electrodes 7 and 8 at 3 Hz @1A, square wave.
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Summary
- A joint ADI/DSTO development
- The array of titanium electrodes spans the length of the sweep (the ship) for spatial accuracy
- The power and control unit is housed within a turbine powered towed body (TBG)
- No external power is required for this 'clip on' addition to AMAS
Contact Details
For further information relating to mine countermeasures, please contact the General Manager Mine Countermeasures,
Jack Byrnes
ADI Limited
Building 314, Level 1
Garden Island NSW 2011
Tel: +61 2 9562 2991
Fax: +61 2 9562 2988
Email: jack.byrnes@adi-limited.com
