VLT
®
Soft Starter Pocket Guide 35
Type 1 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. The soft starter may or may not be operational after the fault.
Type 1 protection is provided by HRC fuses or a MCCB within the motor branch
circuit, which must be able to bear the required motor start current.
Typical selection criteria are as follows:
Rating (% Motor FLC),
Start Current
Starter
type
Protection Type < 350% FLC
15 seconds
> 350% FLC
15 seconds
MCD200 Fuse (non time delayed) 175% 200%
Fuse (time delayed) 150% 175%
MCCB* 150 – 200%
MCD3000 Fuse (non time delayed) 150%
Fuse (time delayed) 125%
MCCB* 150 – 200%
* Consult the manufacturer’s specifi cation.
Maximum fuse ratings for Type 1 motor protection are specifi ed in UL
and IEC standards.
Fuse Rating (% Motor FLC)
Fuse (non-time delayed) 300%
Fuse (time delayed) 175%
Short Circuit Protection: What is required for Type 1 short
circuit protection of a soft starter?
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