Short Circuit Protection, Type 2 - Danfoss VLT Pocket Manual

Short Circuit Protection: What is required for Type 2
short circuit protection of a soft starter?
Type 2 protection requires that in the event of a short circuit on the
output of a soft starter the fault must be cleared without risk of injury
to personnel or damage to the soft starter.
Type 2 protection is provided by semiconductor fuses, which must be
able to carry motor start current and have a total clearing I2t less than
2
the I t of the soft starter SCRs.
Semiconductor fuses for Type 2 circuit protection are additional to HRC
fuses or MCCBs that form part of the motor branch circuit protection.
Refer to the soft starter's Design Guide for semiconductor fuse
recommendations.
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36 VLT Soft Starter Pocket Guide