Cost-efffective motor protection by new aM-fuse

Co-ordination type 1 allows damage to conductors and thermal overload relays after a short-circuit. The subsequent inspection of the starter is the operator's responsibility, as is the possible need to replace the
apparatus. If this is not done, the circuit is not protected against overload, which can lead to motor damage and cable fire.
Co-ordination type 2 guarantees that the starter is in full operation after a short-circuit. This co-ordination type is being adopted as a general requirement in many safety regulations.
Protection in accordance with co-ordination type 2 is achieved by using fuse links, even at 690 V, whereas using circuit breakers would need a current limiting capability in order to be reliable at higher
voltages. In most cases, it would also be necessary to over-dimension the contactors, and the thermal relays must be equipped with current transformers. Thus, an item of equipment that conforms with co-ordination
type 2 using circuit breakers, can be 100% more expensive than one which uses fuse links.

High operation voltage leads to high savings
Reliable operation at higher voltages is very important as there is a tendency to move from a 400 V supply system to a 690 V supply. These higher voltages allow low voltage motors to be utilised instead of medium
voltage motors, even for extremely heavy duty. Also, considerable savings are achieved in cable installation costs. For instance, in a recent electrification of a pulp factory, a 690 V supply system protected by ABB
Control fuses is said to have saved US$ 2M compared to a 400 V system.
Selectivity is easy to achieve using fuse protection, as fuses are selective throughout the whole current range and it can be obtained without the need for complicated calculations. This selectivity means
that only the fault point will be separated from the rest of the network, avoiding the danger of a total blackout.
Fuse links are easy and quick to replace and purchase costs are said to be lower than for circuit breakers. Fuses also maintain a stable material
quality as they are not affected by their surroundings. Their protection characteristics, therefore, remain unchanged year after year. Corrosion cannot damage the inside of the fuse link, which can happen easily with
circuit breakers. After tripping, the only action needed is to change the fuse link.
According to the manufacturer the major benefit of fuse protection is safety. When a fuse link has been removed, there is a totally reliable, visible break point in the network./ins

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For further information contact:
ABB Control Oy P.O. Box 622
FIN-65101 VAASA
FINLAND
Phone: +358 10 22 4000
Fax: +358 10 22 45708

For further information contact:
ABB Capacitors Ltd.
322 Moo 4 Sukhumvit Road,
Bangpoo Ind. Est.
Phraksa, Muang District
SAMUTPRAKARN 10280
THAILAND
Phone: +66 2 3240505
Fax: +66 2 3240503