The virtually silent operation of vacuum contactors in the DILM1000 and DILH2000 ranges from Moeller Electric has proved to be an important benefit for ERA Technology.

The virtually silent operation of vacuum contactors in the DILM1000 and DILH2000 ranges from Moeller Electric has proved to be an important benefit for ERA Technology, one of the UK's leading electrical and electronic equipment testing organisations. The contactors are used in ERA's high-current electrical test facility where most of the work involves testing fuses and circuit breakers to ensure that they meet international standards for safe operation. The facility, which can carry out tests at voltages from 90V to 1.1kV and at currents up to 6kA, was recently relocated to a new building which it shares with administrative staff.

In the new location, the sudden loud noise produced by the operation of the existing air-break contactors was found to be unacceptably disruptive.

To address this issue, Moeller Electric proposed the use of its DILM and DILH contactors which are available with ratings up to 2000A.

Since the higher rated contactors in these ranges use vacuum switches, there is no noise whatsoever from the breaking of the arc.

Only mechanical noise is produced and even this is minimised as the magnet system features electronic control which ensures smooth operation.

In order to achieve the precise timing required - the test current must be applied for exactly five cycles - two contactors would be used.

A DILM1000 contactor, with a thermal rating of 1,000A per pole, would make the current, while at DILH2000 contactor, with a thermal rating of 2,000A per pole would break it.

Both contactors are three-pole devices but, as this is single-phase application, the poles would be connected in parallel to increase current-carrying capacity.

While this solution appeared attractive, the unusual nature of ERA Technology's application meant that further investigation was necessary.

In particular, it was essential that the larger contactor should be able to break currents as high as 10kA on a regular basis, without sustaining damage or undue contact wear.

'The technical support we received from Moeller Electric was superb,' said Dave Treagus, head of electrical testing at ERA Technology.

'The company's engineers examined our application carefully and were quickly able to confirm that the DILH2000 contactor would not only break 10kA reliably, it could even be used up to 17kA.

Similarly, they confirmed that the operating conditions for the smaller DILM1000 contactor were well within its capabilities.' With confirmation that the contactors were easily capable of the required duties, the test installation was quickly adapted to use them.

'Not only are the new contactors meeting all our expectations,' said Dave Treagus, 'they are also providing us with a useful bonus - they require virtually no maintenance, whereas regular attention was always necessary to keep the air-break units in good working order.' As their use at ERA Technology has amply demonstrated, Moeller Electric DILM and DILH contactors provide reliable high current switching in even the most demanding applications.

The range includes both air-break and vacuum products, which between them cover AC1 ratings from 20A to 2000A.

All sizes are available in three-pole versions, and four-pole models are also available with ratings up to 800A.

Optional accessories include auxiliary contacts and protection devices for use in motor starting applications