Hitachi Magnetic Bearing Centrifugal Chiller VM Series

The Hitachi magnetic-bearing centrifugal compressor is designed to maximize energy efficiency and reliability. One of the key features of this chiller compressor is its high-speed direct transmission design, which eliminates the need for speed-increasing gears and reduces transmission loss. Another important feature of the Hitachi magnetic bearing centrifugal compressor is its use of magnetic bearings instead of traditional mechanical bearings. This eliminates the need for lubricating oil, which reduces mechanical loss and maintenance requirements. Combined with Hitachi's high-efficiency closed-type two-stage impeller, the VM series centrifugal chiller achieves a high level of energy efficiency. In fact, under standard GB operating conditions, the chiller can achieve a full load COP as high as 7.0 and an IPLV as high as 9.5. Magnetic bearing technology offers several advantages over traditional oil-lubricated bearing solutions. It uses magnetic fields to levitate the rotor, eliminating the need for physical contact between the rotor and stator. This oil-free operation not only simplifies the system's structure but also reduces the energy losses caused by friction in traditional bearings. Moreover, magnetic bearings have no mechanical wear and tear, reducing chiller maintenance requirements and increasing system reliability. They also eliminate the need for complex oil lubrication systems in chillers, which can be costly to maintain and negatively impact heat exchanger efficiency. By utilizing a permanent magnet motor as a direct-drive impeller instead of a conventional gear-based system, the compressor achieves a simpler transmission mechanism with fewer moving parts, which significantly reduces the failure rate and enhances reliability. The adoption of a permanent magnet motor leads to a reduction of up to 66% in the number of delicate and consumable parts compared to a conventional compressor.

The magnetic-bearing centrifugal chiller unit has a standard emergency power-off protection system. If a power failure happens, the permanent magnet motor will rotate inertially to generate electricity and apply brakes. The energy produced is then stored in the frequency converter and used to power the magnetic bearing, maintaining the shaft's suspension state until the unit comes to a complete stop. This helps to prevent the shaft from falling directly onto the bearing and potentially damaging the magnetic chiller unit's lifespan. When evaluating the impact of a chiller unit on the environment, noise is an important factor to consider. The VM series centrifugal chiller unit adopts magnetic bearings, which completely suspend the moving parts and eliminate friction during operation. This results in a low operating noise of only 76dB(A), which is 5-10 decibels less than that of ordinary centrifugal chillers. Lower noise levels create a more comfortable environment in the computer room, allowing operators to control the system more effectively. The absence of a lubricating oil system in this magnetic-bearing chiller unit significantly reduces maintenance costs by eliminating the need for oil replacement, oil filter replacement, dryer replacement, replacement parts, and associated labor costs. Meanwhile, this oil-free chiller unit features a pre-mounted inverter panel, and all the necessary wiring between the components is completed at the factory. This design eliminates the need for additional power and control wiring between the inverter panel and the chiller unit, which would typically require extra investment from the customer. Additionally, the integrated inverter panel saves installation space in the machine room.