Variable Frequency Technology For Chillers

1.Variable frequency function and characteristics

Frequency conversion is to change the power supply frequency to adjust the load, reduce power consumption, reduce losses, and extend the service life of the equipment. The core of the frequency conversion technology is the inverter, which realizes the automatic adjustment of the motor operating speed rate through the conversion of the power supply frequency, and changes the fixed grid frequency of 50 Hz to a variable frequency of 30-130 Hz.

The compressor is the most important energy-consuming component of the chiller unit. Its speed directly affects the power consumption of the unit. The frequency conversion unit directly adjusts the compressor speed during part of the load. Compared with the ordinary unit through the capacity adjustment valve to adjust the load, the motor speed cannot be changed. Save more power. And the chiller unit is in partial load operation for more than 95% of the working hours, so the variable frequency chiller unit can bring continuous energy saving effect and can recover the investment cost in a relatively short time.

The VFD chiller unit adopts the onboard frequency conversion drive technology, and cooperates with the frequency conversion special compressor, so that the part load energy efficiency of the chiller unit is greatly improved, and the integrated part load performance coefficient (IPLV) can reach more than 10. The variable frequency chiller unit has a soft start function to reduce the impact of the starting current; the inverter has its own DC reactor to minimize harmonic interference; there is also a low harmonic filter option, which is in line with IEEE- 519 under the input power of the inverter regulates harmonic distortion, and also has harmonic filter over-temperature protection and capacitor switching functions.

The biggest feature of the inverter chiller unit is the addition of the inverter output to drive the compressor, and its starting current is 60% lower than that of the traditional equipment driver. In addition to the compressor can use frequency conversion control, fans, water pumps, etc. can also use frequency conversion control.

The load of the chiller unit can realize 1Hz stepless load adjustment each time through the frequency converter. The frequency conversion range is 30-130Hz. With the adaptive control logic, the outlet water temperature can be accurately controlled within plus or minus 0.3 degrees to meet the high-precision temperature control requirements.

2.Variable frequency chiller applications

The inverter chiller has a wide range of applications, such as: variable frequency centrifugal chiller, VFD screw chiller, VFD scroll chiller, variable frequency integrated industrial chiller, VFD hot water chiller unit, etc.

(1)Variable frequency centrifugal chiller

The VFD water cooled centrifugal chiller unit adopts Hanbell variable frequency centrifugal compressor,  independently developed and produced high-efficiency heat exchanger, and adopts precise liquid level control technology to ensure that the evaporator is always in an efficient heat exchange state. The condenser adopts droplet separation technology to ensure efficient and full heat exchange of the condensation heat exchange tube. The IPLV of the chiller unit is as high as 10. Chilled water outlet temperature range: 5-20℃. In addition to standard specifications, various non-standard units can be customized according to user requirements. Frequency conversion range: 30Hz-50Hz

(2)Variable frequency screw chiller

Water-cooled variable frequency screw chiller unit adopts VFD twin screw compressor, matching the self-produced high-efficiency condenser and evaporator, and branded expansion valve. Chiller application range: various large and medium-sized air conditioning cooling commercial sites, and industrial sites such as chemical, pharmaceutical, industrial processing equipment, and food processing. The chilled water outlet temperature is 5-20℃, and the cooling water temperature range is 15℃-40℃.

Frequency conversion range: 20Hz-80Hz

(3)Variable frequency scroll chiller

Water cooled VFD scroll chiller equips with branded variable frequency compressors and branded inverter, adopts  high-efficiency shell and tube condenser and evaporator. The chiller unit is controlled by a microcomputer, equipped with multiple protection functions, and has high reliability. Designed for comfortable air-conditioning, suitable for various commercial buildings such as hotels, shopping malls, office buildings, etc. Chiller includes two series, open type and cabinet type.

Frequency conversion range: 30Hz-50Hz

(4)Variable frequency air conditioning chiller

Air source inverter air conditioner chiller unit adopts an enhanced special inverter compressor, and independently developed and manufactured high-efficiency evaporator and condenser with COP more than 3.2. The chiller unit can be designed single and double circuits to meet the different choices of customers. For double circuit chiller, when a compressor fails, the other compressor can still operate normally, so as to minimize the impact of the failure. Heat recovery can be optional. The chiller is suitable for various commercial buildings such as hotels, shopping malls and office buildings.

Frequency conversion range: 20Hz-80Hz

(5)Variable frequency integrated chiller

The variable frequency industrial chiller unit is an integrated designed for the industrial field. The chiller unit integrates the VFD chiller, water tank, cooling water pump, process chilled water pump, piping system, various valves, and engineering control cabinets. The integrated industrial chiller features reliable quality, compact structure and high integration. The installation is simple and convenient, reducing engineering installation costs.

Frequency conversion range: 20Hz-80Hz