To deliver a load greater than the rating of an existing transformer, two or more transformers can be linked in parallel with one. When the load on one of the transformers exceeds its capacity, the transformers are linked in parallel. The excess load is carried by the remaining transformers.
The maximum load that can be delivered by a pair of transformers is called their parallel capacity. If the total load on all the circuits exceeds this value, then some of the circuits will need more than one transformer to meet the demand.
Loads can also be divided between multiple transformers if they have separate primary circuits. For example, this can be done if each transformer is supplying power to a different part of a complex circuit board pattern. In this case, the board manufacturer would ensure that no two parts of the board were powered up by the same transformer.
In general, multiple transformers can be used in parallel if they have separate primary circuits and if their total combined capacity is large enough to supply all the current needed by all the circuits.
For example, a system might require six 50-60 Hz transformers in parallel to provide over 200 amps at 60 volts. Each transformer would need to be capable of carrying 20 amps at 60 volts, which would mean they could not have shared windings or cores.
Before you may connect transformers in parallel, three requirements must be satisfied. 1. The transformers' primary and secondary voltage ratings must be the same. Large circulation currents will flow in both the main and secondary windings if the voltage ratings of the transformers are not the same. This could cause damage to the circuitry. 2. The transformer's primary and secondary current ratings should be the same. Otherwise, large circulating currents will also flow in the primary circuit of the second transformer.
3. Both the primary and secondary circuits of each transformer must have a ground connection. Without a common ground, positive charges will build up on the surface of the secondary winding of one transformer and negative charges on that of the other transformer. When this happens, large amounts of electricity will be drawn from or supplied to these circuits, which can cause damage to the equipment.
4. All connections between the transformers must be properly protected against electrical shock by either metal clamps or rubber boots.
Transformer with Multiple Windings Secondary windings can be coupled in a variety of ways to generate a larger voltage or current supply. It should be noted that linking parallel transformer windings together is only feasible if the two windings are electrically similar. If one winding has more wire than the other, then there will not be enough wire to link them all together.
Here are some examples of how multiple windings on a single transformer can be used:
1 Couple several small-voltage transformers in series to increase voltage.
2 Use a large-voltage transformer as a backup power source. When primary power is lost, the secondary side of the transformer will provide power to essential equipment such as computers and lighting systems.
3 Tie two or more autotransformers together to increase their output capacity.
4 Connect two or more split-phase transformers together to increase their voltage rating.
5 Combine two or more single-phase transformers into a multi-tap system for use with solar panels or wind turbines.
6 Use a double-transformer design with one set of primaries connected to the sun and another set connected to an electrical outlet to get continuous power even when the sun isn't shining or the grid is down.