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PRESS RELEASEMarch 7 1997
Cost-effective motorprotection by new aM-fuse
New aM fuses from ABB Control meet the latestregulations for
motor protection more economicallyand conveniently than general
purpose fuse linksand circuit breakers. In the new IEC
947-4-1standard for motor starters, co-ordination categoriesare
defined for protection.
Co-ordination type 1 allows damage to conductors and thermal
overload relaysafter a short-circuit. The subsequent inspection of
the starter is the operator'sresponsibility, as is the possible
need to replace the apparatus. If this is notdone, the circuit is
not protected against overload, which can lead to motordamage and
cable fire.
Co-ordination type 2 guarantees that the starter is in full
operation after ashort-circuit. This co-ordination type is being
adopted as a general requirementin many safety regulations.
Protection in accordance with co-ordination type 2 is easily
achieved by usingfuse links, even at 690 V, whereas using circuit
breakers would need a currentlimiting capability in order to be
reliable at higher voltages. In most cases, it
would also be necessary to over-dimension the contactors, and
the thermalrelays must be equipped with current transformers. Thus,
an item of equipmentthat conforms with co-ordinationtype 2 using
circuit breakers, can be 100% more expensive than one whichuses
fuse links.
High operation voltage leads to high savingsReliable operation
at higher voltages is very important as there is a tendency tomove
from a 400 V supply system to a 690 V supply. These higher
voltagesallow low voltage motors to be utilised instead of medium
voltage motors, evenfor extremely heavy duty. Also, considerable
savings are achieved in cable
installation costs. For instance, in a recent electrification of
a pulp factory, a690 V supply system protected by ABBControl fuses
saved US$ 2M compared to a 400 V system.
Selectivity is easy to achieve using fuse protection, as fuses
are selectivethroughout the whole current range and it can be
obtained without the need forcomplicated calculations. This
selectivity means that only the fault point will beseparated from
the rest of the network, avoiding the danger of a total
blackout.
Fuse links are very easy and quick to replace and purchase costs
are muchlower than for circuit breakers. Fuses also maintain a
stable material quality asthey are not affected by their
surroundings. Their protection characteristics,therefore, remain
unchanged year after year. Corrosion cannot damage the
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inside of the fuse link, which can happen easily with circuit
breakers. Aftertripping, the only action needed is to change the
fuse link.
Furthermore, the major benefit of fuse protection is safety.
When a fuse linkhas been removed, there is a totally reliable,
visible break point in the
network./ins
Captions:The new aM-fuse links introduced by ABB Control offers
extremely affordablemotor protection.
For further information contact:ABB Control Oy
P.O. Box 622FIN-65101 VAASAFINLANDPhone: +358 10 22 4000Fax:
+358 10 22 45708
