Cooling Water Pump Retrofit with a Permanent-Magnet Motor in Zhangjiagang

A cooling water pump is the component that makes a cooling loop work. Its job is to give chilled water — or a water and glycol mixture — the pressure to circulate continuously, carrying heat away from the chiller that produced it and delivering it to the place where it is rejected. If the pump stops, the whole temperature control function stops with it, which is why the drive's protection and signalling matter as much as its energy performance.

This project converted the pump from an asynchronous motor to a permanent-magnet synchronous machine on a Yolico drive. The motor is rated 75 kW at 1500 rpm with a full-load current of 125 A, and runs at a rated frequency of 100 Hz. The drive selected was a YZJ580E T4-75G/90P-T rated 150 A — comfortably above the motor's 125 A, which is the correct way round for a PMSM where the drive has to supply the magnetising requirements of a permanent-magnet rotor at every speed.

Two aspects of the installation were dictated by how the plant operates the loop. The pump has to be startable and stoppable both from the local panel and from the control room, so a local/remote selector switch was fitted on the cubicle door, with the drive configured for terminal-based run command so both paths work. And the plant's PLC needs to know the state of the machine, so run and fault signals are passed back through contactors and interposing relays — run on the drive's own relay output, fault on an extension relay.

The drive parameters were set to the motor as built rather than to a generic motor model: rated power 75 kW, rated voltage 380 V, rated current 125 A, rated frequency 100 Hz, rated speed 1500 rpm, with the running frequency set to 100 Hz. Free-run stop was selected as the stop mode, which suits a pump that has no flywheel duty and where the priority is to avoid the drive fighting a coasting impeller.

Commissioning finished with the usual PMSM discipline. Once the parameters were entered, the drive was put into static auto-tuning and the motor's electrical characteristics were measured with the shaft stationary. On first run the three-phase output current at 100 Hz read 88 to 90 A, balanced across all three phases — which is the check that matters after a permanent-magnet retrofit, because an unbalanced or unexpectedly high current at a known speed points to a parameter or wiring error rather than to the motor. The unit has run stably since.