Scope: Main 3-phase power circuit from customer supply to main compressor motor MM in delta run mode.. This is the primary energy path on the drawing; control and fan circuits are auxiliary.
Boundary: Source = customer L1/L2/L3 supply; sink = Main Motor MM.. The drawing starts at the customer position terminals and ends at the motor.
Can fail: breaker, other. Breaker, fuses, terminal block, contactors and overload relay are the discrete power-path devices that can fail open; the supply and motor are the boundary end points.
Success: any_path. Main motor runs in delta only when KM01 (U1/V1/W1 ends) and KM03 (W2/U2/V2 ends) are both closed, so they are modelled as a series chain; any path then means all required devices work.
Not modelled:
- Control circuit (TR1, FU01-FU05, S01, K01-K09, ES4000T controller, coils, RC snubbers, PH01 phase relay): Kept to the main power circuit; control-side failures that drop the contactor coils are a separate dependency.
- KM02 star contactor: Used only during star start; in steady delta running it is open and not on the power path.
- Cooling fan CLF branch (KM04, FR02): Separate load; its loss trips the compressor via controller but is not on the main motor power path.
- KM01/KM03 drawn as series: Electrically they feed opposite winding ends in parallel wiring, but both are required, so series reflects the reliability logic.