How to choose the ATS BREAKER for the generators?

Let's take 750KVA 50HZ/400V 3phase genset as the example.

1. Calculate the Generator’s Rated Current
   Parameters:
   P=750 kVA=750,000 VA
   V=400V
   Calculation:
   I=750/1.732×400 ≈1082.5A

Select ATS Rated Current
Basic Requirement: The ATS’s continuous current rating must be ≥ 1082.5 A.
Recommended Specification:
Choose a 1250 A ATS (common industrial-grade standard, e.g., Schneider, ABB).
Provides ~15% margin to accommodate transient overloads or future capacity expansion.

3. Key Selection Parameters
Number of Poles:
3P4W (Three-Phase Four-Wire) for 400V systems (includes neutral line).
Transfer Time:
Millisecond-level switching for sensitive loads (e.g., data centers).
Seconds-level switching acceptable for general loads.
Control Logic:
Must be compatible with the Cummins generator controller (supports automatic start/transfer signals).
Short-Circuit Capacity:
ATS’s short-circuit breaking capacity must exceed the system’s maximum short-circuit current (verify grid parameters).

4. Recommended Configuration Example
ATS Model: Schneider Electric Compact NSX 1250N
Rated current: 1250 A
Poles: 4P
Short-time withstand current: 65 kA
Additional Features:
Voltage/frequency monitoring module.
Integration with generator controller for coordinated operation.

5. Final Recommendation
Select a 1250 A, 3P4W ATS with:
Verified short-circuit capacity and environmental adaptability (e.g., temperature, dust).
Critical: Validate all parameters with a professional electrical engineer before implementation.