why semiconductor fuse used in drive ,not ordinary?

Answer Posted / harish nair

Basically a drive means cluster of thyristors, these thyristors may fail when subject to 10mS(one half cycle in a 50 Hz system)pulse of only 10 times the RMS value of normal current.A normal fuse requires 15 to 30 times of its nominal ampere rating to melt with in 10mS, which is not fast enough to provide the protection, whereas a semiconductor fuse requires only 5 to 6 times it ampere rating to defuse thus ensuring fast action & protection to thyristor. It has a exponentional decay graph the greater the current the lesser operation time.

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