Evaporative-Condenser Chiller Unit: A Liquid-Cooled Drive for a Magnetic-Levitation Compressor

The evaporative-condenser integrated chiller works on a chilled-water loop. Chilled water is the medium that carries cooling capacity: it exchanges heat with the refrigerant inside the evaporator, gives up its heat to the refrigerant, is pumped through pipework to the air-handling devices that need it, picks up heat from the air being treated, and returns to the evaporator to start again. The compressor is the heart of the cycle — it draws low-pressure refrigerant gas off the evaporator, compresses it into hot high-pressure gas, discharges it to the condenser, and there the gas gives up its heat to the chilled water and condenses to a low-temperature, high-pressure liquid.

This particular unit uses a magnetic-levitation compressor. The shaft is held by magnetic bearings and spins without mechanical contact, which removes the oil system and the friction losses — but it also means the drive has to control the shaft very precisely. Speed stability is not a comfort feature on this compressor; it is what keeps the shaft off its touchdown bearings.

The drive specified from the compressor's parameters was a 160 kW unit rated 300 A in the liquid-cooled form. Liquid cooling was not a preference but a consequence of where the drive lives: the panel is inside a packaged chiller, and an air-cooled drive in that position would draw in the moisture and dust-laden air the unit itself is generating. Cooling the drive through the unit's own water circuit keeps the electronics sealed.

The customer also asked for a sine-wave filter between drive and motor, which is common on machines with long motor cables or with windings that need relief from fast switching edges. Commissioning had to respect the order of operations: with the filter out of circuit and no load on the shaft, the motor parameters were learned first — 2× phase resistance, and 2× phase inductance. Only afterwards were the filter's own parameters downloaded to the drive board, in each case as phase inductance and phase resistance, and the corresponding parameters changed so the filter model took effect. Connecting the filter's capacitors directly to the drive output is not permitted, and the wiring was arranged accordingly.

The unit then ran through every operating condition the customer specified, and the drive held the compressor stable at all of them. That is the useful outcome to report: not a single headline efficiency number, but confirmation that a liquid-cooled drive with a correctly commissioned sine filter handles the full duty envelope of a maglev chiller — which is what a packaged-unit builder needs before committing a drive to a production design.