A star delta is used to prevent the across the line current draw when a motor starts. Many utility companies will not allow more than 20 HP to be started across the line. A three phase fryer uses resistive elements in it to heat the oil. Resistive loads must use the full voltage that is recommended by the manufacturer, for the equipment to operate at the recommended wattage that is on the equipment's nameplate.
why three phase induction motor is delta connected
An open delta connection is a delta connection with one phase removed, but still supplied with three line conductors. An open wye is a wye connection with one phase removed, supplying a three line conductors and a neutral conductor. An open-delta/open-wye is a method of providing a reduced-load three-phase supply using just two single-phase transformers, rather than the preferred method of using three single-phase transformers.
Star and delta connection
The phase shift in three-phase transformer from winding of Transformer and determine by vectorgroup of transformer such as YNd1 High voltage connect to wye Low Voltage connect to delta so L.V. lag H.V 30 degree.Answer'Phase shift' or, more accurately, 'angular displacement', is the angle between the secondary line voltages and primary line voltages of a three-phase transformer.
There are various ways in which you can connect a three-phase transformer's primary and secondary windings, or in which you can connect three single-phase transformers to create a three-phase transformer bank. For example: wye-wye, wye-delta, delta-delta, delta-wye, etc.For each connection, there is a natural phase shift between the primary and secondary line voltages. This is called the angular displacement (or 'phase displacement') of the transformer connection.If you wish to parallel two three-phase transformers, or two three-phase transformer banks, then their angular displacements must be the same (there are also other requirements not relevant to this answer).A vector group is a method of specifying a three-phase transformer (or transformer bank) method of connection and its angular displacement. Transformer connections from the same group can be paralleled. Those in different groups cannot
The nominal voltages for a home service utility in North America is single phase 120/240 volts. By special permission a home will be allowed a three phase connection. The only voltage close to that is 240 volts three phase delta. In Canada three phase delta is not used any more and is replaced with a three phase four wire system of 120/ 208 wye connection. The wye connection is used primarily in commercial, industrial and apartment building services.
A star connection is where the three phase nonpolarities are tied to a single point, and very often grounded. A delta connection is where the nonpolarity of one phase is tied to the polarity of another phase, forming a greek delta shape. If measuring from polarity to nonpolarity on a single phase, in the star formation you are looking at L-N voltages; in the delta connection, you are looking at L-L voltages (L-N voltages * square root of three).
One must check the design of the transformer windings. STAR - Delta or Star to star or Delta - star or Delta Delta. Wiring must be done accordingly.
A delta-connected system is described as being a three-phase, three-wire, system, and doesn't have a neutral. But a balanced star (wye) connected load (e.g. a three-phase induction motor) doesn't actually require a neutral.
The open Delta or V-Connection transformer is an improvement of the 1 three-phase transformer. The open Delta transformer can restore power in a Delta-Delta three-phase bank when one of the three single-phase transformers, which can be individually disconnected and replaced in case of failure, breaks down. The open Delta transformer then allows functionality to be restored, but at a reduced power of 57.7 of the original power.
One of the three phase contacts in the star contactor could be burned open or just open not allowing the motor to start because of a single phase condition. The time interval between star and delta connections could be small enough that the motor heaters will not catch the single phase condition and trip. When the motor goes into delta (which is now across the line starting) all of the three phase contacts in the contactor close and the motor starts.
circuit characteristics.