Often, a simple control scheme using a microprocessor can allow manufacturers to use lower starting torque compressors without the use of a hard start kit to operate their ice machines. Before the advent of the microprocessor, many ice machine manufacturers used capacitor-start/capacitor-run (CSCR) compressor motors in their equipment. CSCR compressor motors used a potential relay, a start capacitor, and a run capacitor to help get started against uneven system pressures. These components were often referred to as a “hard-start-kit” (Figure 1).
Hard start kits were effective, giving the CSCR motor relatively high-starting and good running torque. The potential relay consisted of a normally closed set of contacts and a high-resistance coil. At the instant of start, both the start and run capacitors are in parallel with one another while at the same time being in series with the start winding.