Short-Circuit Protection Devices; Type 1 Coordination; Type 2 Coordination; Iec Coordination With Short-Circuit Protection Devices - Danfoss VLT MCD 600 Operating Manual

Operating Guide | VLT® Soft Starter MCD 600

3.11 Short-circuit Protection Devices

When designing motor circuit protection schemes, the IEC 60947-4-1 standard on soft starters and contactors defines 2 types of
coordination regarding soft starters:
•

Type 1 coordination.

•

Type 2 coordination.

3.11.1 Type 1 Coordination
Type 1 coordination requires that, if there is a short circuit on the output side of a soft starter, the fault must be cleared without risk of
injury to personnel and damage to installations. There is no requirement that the soft starter must remain operational after the fault.
For the soft starter to become operational again, repair and replacement of parts are required.
HRC fuses (such as Ferraz/Mersen AJT fuses) can be used for Type 1 coordination according to the IEC 60947-4-2 standard.
3.11.2 Type 2 Coordination
Type 2 coordination requires that, if there is a short circuit on the output side of a soft starter, the fault must be cleared without risk of
injury to personnel or damage to the soft starter.
Type 2 coordination has the advantage that, after the fault is cleared, authorized personnel can replace the blown fuses and check
contactors for any welding. The soft starter is then operational again.
Semiconductor fuses for Type 2 circuit protection are extra to HRC fuses or MCCBs that form part of the motor branch circuit
protection.
DC BRAKE
A high brake torque setting can result in peak currents up to motor DOL being drawn while the motor is stopping.
Ensure that protection fuses installed in the motor branch circuit are selected appropriately.
-
NO BRANCH CIRCUIT PROTECTION
Integral solid-state short-circuit protection does not provide branch circuit protection.
Provide branch circuit protection in accordance with the National Electrical Code and any additional local codes.
-

3.12 IEC Coordination with Short-circuit Protection Devices

These fuses were selected based on a start current of 300% FLC for 10 s.
Table 8: IEC Fuses
Nominal rating [A]
MCD6-0020B 24
20 | Danfoss A/S © 2018.10
C A U T I O N
C A U T I O N
2 2 Type 1 coordination 480 V AC, 65 kA
SCR I t (A s)
Bussmann NH fuse links
1150 40NHG000B
System Design
Type 2 coordination 690 V AC,
65 kA Bussmann DIN 43 653
170M3010
AQ262141844215en-000202 / 175R1174