Transformer Delta-Delta Connection

Fig: Delta-Delta or ∆-∆ Connection

Delta-Delta Connection Procedure of Three-Phase Transformer in Power Transmission Network 

This connection is economical for large, low-voltage transformers in which the insulation problem is not so urgent, because it increases the number of turns/phases. 

Carrier 23XRV High-Efficiency Variable Speed Screw Chiller

Fig: a 3D sectional view of a screw compressor

Carrier 23XRV chiller is the world’s first integrated variable-speed screw chiller

Carrier’s Evergreen® 23XRV chiller is the world’s first integrated variable speed, water-cooled, screw chiller. It incorporates significant breakthroughs in water-cooled chiller technology to provide excellent reliability and achieve superior efficiencies at true operating conditions all without compromising the environment.

The 23XRV chiller provides:

• High efficiency: variable speed, positive displacement screw compressor.
• High-performance: certified to 0.299 kW/ton AHRI IPLV.
• Environment-friendly: chlorine-free HFC-134a refrigerant.
• Low harmonic distortion: IEEE-519-compliant.
• Versatile: an ideal solution for constant and variable flow pumping systems.

High Efficiency Chiller

Next-generation technology: The 23XRV incorporates high-efficiency screw compressor technology with an innovative tri-rotor design.

Energy efficiency: This refrigerant-cooled, variable frequency drive (VFD) chiller has the ability to reduce speed and optimize operation independent of ambient conditions. This unique capability permits the chiller to precisely match the building load and conserves energy.

High part-load performance: IPLV to 0.299 kW/ton(Air Conditioning, Heating, and Refrigerant Institute (AHRI) integrated part-load value)

High-performance tubing: Carrier's Evergreen chillers utilize advances in heat transfer technology, providing compact, high-efficiency heat exchangers. Tubing with advanced internally and externally enhanced geometry improves chiller performance by reducing overall resistance to heat transfer while reducing fouling.

FLASC sub-cooler: Located at the bottom of the condenser, the Flash sub-cooler (FLASC) increases the refrigeration effect by cooling the condensed liquid refrigerant to a lower temperature, thereby reducing compressor power consumption. 

AccuMeterTM flow regulation: Regulating refrigerant flow according to load conditions, the AccuMeter system provides a liquid seal at all operating conditions and eliminates unintentional hot gas bypass.

Environmental Leader Screw Chiller

Sustainable long-term solution: The Evergreen 23XRV screw chiller epitomizes Carrier's long-held commitment to the environment and its dedication to innovation. The 23XRV offers customers a long-term, high-efficiency, chlorine-free chiller solution that will not be affected by refrigerant phaseouts.

Chlorine-free refrigerant: Carrier's decision to utilize non-ozone-depleting HFC-134a refrigerant lets customers select a safe and environmentally sound product without having to compromise on efficiency.

Reliability of screw compressor

Advanced tri-rotor compressor: The tri-rotor compressor used in the 23XRV has been designed for extremely high reliability. It features balanced rotor geometry and shorter screw lengths, resulting in vastly reduced compressor bearing loads and a minimum L10 compressor bearing life in excess of 500,000 hours when operated at Air-Conditioning and Refrigeration Institute (ARI) standard conditions.

Superior oil management: All Evergreen 23XRV chillers regulate oil temperature, viscosity, and pressure. Rather than relying on differential system pressure to lubricate the compressor, the 23XRV uses a patented process to ensure that high-quality oil is delivered to the compressor bearings via a positive displacement pump. This allows continuous operation with cold condenser water at all loads. Should the input power to the chiller be lost, the system is designed to assure proper lubrication of the bearings during cost down.

Refrigerant-cooled VFD: Refrigerant cooling of the variable frequency drive (VFD) minimizes VFD size and ensures proper cooling of the transistors for extended life. Using R-134a refrigerant instead of water also eliminates costly maintenance of the water cooling pump, heat exchanger, and rubber tubing used with water-cooled VFDs.

Cooler tube expansion: The cooler tube is fitted with expansion values at center support sheets to prevent unwanted tube movement and vibration, thereby reducing the possibility of premature tube failure. The tube wall is thicker at the expansion location, and at support and end-tube sheets, in order to provide maximum strength and long tube life.

Double-grooved end-tube sheet holes: The double-groove design provides a more robust seal than single-rolled joints, reducing the possibility of leaks between the water and refrigerant sides of the chiller.

Advanced design 23XRV chiller

Low harmonic distortion: The Evergreen 23XRV chiller generates less than 5% total harmonic distortion at the input to the variable frequency drive (VFD) without the use of any external filters or line reactors. This ensures that the VFD cannot exceed the IEEE-519 standard for distortion at the point of common coupling. The integrated VFD provides a soft start, further reducing stress on the compressor and inrush current at start-up.

Fully charged at shipment: 23XRV chillers can be shipped fully charged with refrigerant from the factory, minimizing the time required for start-up. Furthermore, an option for in-chiller refrigerant storage reduces maintenance time.

Positive pressure design: The positive pressure design used in the 23XRV ensures that air, moisture, and other performance-degrading contaminants are not sucked inside the chiller. This eliminates purge units and their associated maintenance.

Product Integrated Control (PIC III): Carrier's direct digital electronic controls (PIC III) provide unmatched flexibility and functionality. Each unit integrates directly with the Carrier Comfort Network® (CCN) system, providing a solution to control applications.

Get a free download carrier chiller manual: