Sump Pump Inrush & LRA Surge Checker
Sump pumps and inductive induction motors draw an enormous spike in instantaneous current when the rotor starts from a dead standstill. Calculate whether your portable inverter can absorb this surge without tripping.
Understanding Locked Rotor Amperage (LRA)
When an AC electric motor is stationary, there is zero back-electromotive force (back-EMF) to resist the incoming electrical current. For the first 100 to 300 milliseconds, the motor behaves almost like a dead short across the AC terminals. This initial draw is known as Locked Rotor Amps (LRA).
🌊 1/2 Horsepower Motor Reality
A standard 1/2 HP submersible sump pump draws around 800W to 1,050W while running continuously. However, its startup spike frequently peaks between 2,800W and 3,800W for a fraction of a second. A 2,000W rated inverter will immediately shut down into overload fault protection.
⚡ Inverter Peak Surge Durations
Most solar generators specify a peak surge limit (e.g. 4,800W for a 2,400W inverter), but this peak rating is often only rated for 20ms to 500ms before electronic circuit breakers activate to protect the internal MOSFETs.