Locked-rotor amps is the current measured when a motor is energised but held stationary. It represents the worst-case draw at the very start of a compressor's run, before the rotor moves. Compressor manufacturers list LRA alongside the rated running current; for small hermetic compressors it is typically several times the running figure.
In normal operation, a motor draws close to LRA for only a moment. The danger comes when it cannot start, for example because voltage is too low, a start component has failed, or the compressor is trying to restart against high pressure seconds after a power blip. The motor then sits at locked-rotor current until the overload protector trips it, heats up, cools, and tries again.
A technician who measures current close to LRA without the compressor starting knows to look at voltage, start components or a mechanically seized compressor. For buyers and electricians, LRA is useful when choosing breaker curves, generator capacity and stabiliser ratings so starts are not blocked by nuisance tripping.