Rotary-screw compressor Working principle

CPM BOARD Working Principle:

There is one CPM per compressor.  The device controls the compressor contactors, oil 

solenoid, loading/unloading the solenoid, motor cooling solenoid (30XA080,082 only) and the oil separator heater. The CPM also monitors the compressor motor temperature, high pressure switch, oil level switch, discharge gas temperature, oil pressure transducer, motor current, MTA (must trip amps) setting and economizer pressure transducer. The CPM responds to commands from the MBB (Main Base Board) and sends the MBB the results of the channels it monitors via the LEN (Local Equipment Network). The CPM has three DIP switch input banks, Switch 1 (S1), Switch 2 (S2), and Switch 3 (S3). The CPM board DIP switch (S1) configures the board for the type of starter, the location and type of the current transformers and contactor failure instructions. See Table 4 for description of DIP switch 1 (S1) inputs. See Appendix D for DIP switch settings. The CPM board DIP switch S2 setting determines the must trip amps (MTA) setting. See Appendix D for DIP switch settings. The MTA setting which is calculated using the settings S2 must match the MTA setting in the software or an MTA alarm will be generated.