400 VAC Autotransformers
400 VAC autotransformers are used with three-phase power distribution systems where the line-to-line voltage is 400 volts. This voltage level is commonly found in industrial settings and large-scale electrical systems. And the autotransformers of this group allow for adjusting voltages to match specific requirements within the HVAC system.
The series includes 400 VAC autotransformers with screw terminal blocks used in electrical systems to adjust voltage levels. The autotransformers have a single winding with multiple taps, allowing for variable output voltage. The primary purpose is voltage regulation, stepping down the voltage as needed.
The structure includes a laminated core and a winding with multiple taps. The transformers are impregnated with special coating to reduce the noise. The screw terminal blocks provide a secure and reliable means for connecting the transformer to the electrical system.
Connecting two identical autotransformers in a three-phase system is a common practice in electrical engineering, particularly for the regulation of three-phase motors. This method is employed for various reasons, including efficiency, cost-effectiveness, and reliability.
The two autotransformers are connected in an open delta or V-V configuration. This is a method of transformer connection used to transform three-phase power using two single-phase transformers.
How to connect autotransformers in open delta (V-V) configuration
Primary windings connection: Connect one end of the primary winding of each autotransformer to one phase of the three-phase power supply. Next, connect the other end of the primary winding of one autotransformer to the midpoint of the primary winding of the second autotransformer.
Secondary windings connection: Connect one end of the secondary winding of each autotransformer to one phase of the load (e.g., a three-phase motor). Next, connect the other end of the secondary winding of the autotransformer with its midpoint connected to the primary winding midpoint to the remaining phase of the load.
Connecting two autotransformers in this manner allows for the generation of a third phase, which is necessary for three-phase motor operation. The open delta configuration is advantageous because it requires only two autotransformers instead of three, making it cost-effective and efficient.
While the open delta connection is a practical solution, it is essential to consider its limitations, such as lower power capacity compared to a complete three-phase system. Engineers must carefully assess the specific requirements of the application before opting for an open delta configuration.