Why do modern three-phase compressors often require crankcase pressure regulating (CPR) systems?

Modern three-phase compressors frequently require crankcase pressure regulating (CPR) systems primarily to address the challenges associated with pressure fluctuations that can occur after defrost cycles. When a defrost cycle is initiated in refrigeration systems, the compressor may experience a temporary increase in load and can potentially become overloaded if the crankcase pressure is allowed to rise unchecked.

The CPR system works by maintaining the crankcase pressure within a safe range, which prevents excessive loading on the compressor during and after the defrost period. This management of pressure ensures that the compressor can operate efficiently and effectively, avoiding potential damage from overload conditions and improving overall system reliability. Maintaining appropriate pressure levels is crucial in prolonging the life of the compressor and ensuring consistent operation.

The other options relate to various operational improvements but do not specifically address the critical nature of managing crankcase pressure in relation to the overload issues that can arise post-defrost, making the need for a CPR system for modern three-phase compressors most pertinent in this context.