Motor protection circuit breaker, SIRIUS 3RV2021-1CA20-0BA0
The backup fuse recommendation is gG 25 A at 400 V and 500 V, stepping down to gG 20 A at 690 V. That fuse size is the maximum allowed to preserve the breaker's 100 kA rating; a larger fuse would shift the let-through energy above what the breaker can interrupt. Compared to the smaller-frame 3RV2011-0BA20, the 3RV2021-1CA20-0BA0 is the size S0 variant with higher continuous current capacity and the same 100 kA interrupting rating. The 3RV2011-0BA20 is a size S00 breaker with a lower thermal setting range; the 3RV2021-1CA20-0BA0 will not drop into a panel wired for S00 without adjusting the DIN rail mounting clips and terminal spacing. The spring-loaded terminals on this unit are screwless — the S00 sibling often uses screw terminals — so the wiring method differs.
Use a screwdriver with a 3 mm shaft diameter and a 3.0 x 0.5 mm tip to open the clamp — push in, insert the stripped conductor (8-10 mm strip length), release. The 50 mm clearance above and below is for cable bending radius; the 30 mm side clearance is for neighboring devices or auxiliary contact blocks. For a motor feeder that needs ground-fault protection, add an external ground-fault relay or use a 3RV2 variant with the GF option. The rated operating voltage range is 20 to 690 V, covering 24 V control transformers up to 690 V line supplies. The maximum switching frequency at AC-3 duty is 15 operations per hour — adequate for a motor start once every four minutes, not for jogging or rapid cycling.