# Open delta transformer

## Open delta transformer

In power transformation, three-phase transformation of energy can be possible only by using two similar transformers in open-delta configuration as shown in figger. This connection arrangement is also called the V connection. The open-delta connection is often used in an emergency when one of the three transformers in a delta-delta bank becomes defective or in maintenance work.
When it is in good service, a consumer’s three-phase power supply can be restored as soon as possible. The defective transformer can be cut out of service.
The transformer which connection in open delta connection are called open delta transformer.

### Example of open delta transformer

It is show the connection of open delta transformer. The open-delta connection can be used in an emergency. Three 50-KVA transformers each rated at 2.4KV on the high-voltage (HV) winding ad 240 volts on the low-voltage (LV) winding are connected in a delta-delta from figger. This closed-delta bank is used to step down a 2.4KV three-phase input to a 240 volt, three phase output to supply an industrial consumer. If the three-phase power service is interrupted due to lightning strikes, or other natural or man-made accidents and damages one of the transformer, then service must be restored instantly. This situation shown in diagram.
The transformer 3 is the defective transformer. If all of the leads of the damaged transformer are disconnected, and then closed-delta bank automatically becomes an open-delta transformer bank.

### NOTE; for open delta transformer

One transformer is removed; the triangular coil arrangement is open on one side.

Because the schematic diagram resembles the letter V, this arrangement is also called the V connection.
While the total KVA of the open-delta bank should be two-thirds that of a closed-delta bank,the actual KVA rating of an open-delta bank is only 57.7% of the capacity of closed delta bank. Because, the currents of the two transformers in the open delta connection are out of phase, resulting in the total available capacity of the open-delta bank being only 57.7% instead of 66.7%.
In this open-delta example, three 50-KVA transformers connected in a delta-delta bank.
For the closed-delta bank the total KVA capacity is 50+50+50=150 KVA.
When one transformer is disconnected, the transformer bank changes to an open delta connection configuration and the total KVA capacity now is only 57.7 percent of the original closed delta capacity,
150 x.577 = 87 KVA.

#### Application of open delta transformer

Hence it is the open delta connection configuration from above example we can understand open delta connection. Now we will know that application of open-delta connection.
It is the example of open delta transformer

### Application of open-delta connection

The open-delta connection has a number of features that are advantageous
1. The circuit can be employed in an emergency situation when one transformer in a complete delt-delta configuration must be removed for repair and continuity of service is required.
2. Upon failure of the primary or secondary of one transformer of a complete delta-delta circuit, the system can be operated as open delta circuit and can deliver three phase power to a three phase load.
3. A circuit is sometimes installed as open delta circuit with the understanding that its capacity may be increased by adding one more transformer to form complete delta –delta circuit.

### Three phase to six phase conversion method

Four different are used for three-phase to six-phase conversion:
1. Double-star connection
2. Double-delta connection
3. six-phase star connection
4. Diametrical connection
Hence it is the theory of open delta transformer if you will find any incorrect above please comment below.

For knowing more about open delta transformer you must this video.