Using an isolating transformer in UPS, battery charger-rectifier, inverter, and industrial stabilizers has many advantages, some of which are mentioned below:
1- Isolating the input power of the device from the battery and its output, which eliminates the possibility of electric shock on the battery terminals and on the output of the device from the input ground (due to the galvanic isolation provided by the transformer).
2- At the input of industrial chargers (thyristor) by changing the voltage level to the required amount according to the DC voltage level, it improves the input power factor, reduces input current harmonics, reduces output ripple, reduces reactive current, which leads to increased efficiency and then reduced temperature of system.
3- Increasing the short circuit impedance and as a result reducing the maximum short circuit current, which causes less damage to the circuit breaker, power lines, and its path measurement equipment during the short circuit.
4- The low-frequency harmonics of the third, ninth, fifteenth, etc., are reduced on the input side.
5- In the delta connection of the transformer, the zero component of the current is removed and is not transferred to the lines.
6- It is possible to create a 6-phase star, delta, or more phases that industrial chargers have 12 pulses or more by developing the ability to reduce input current harmonics, reduce output ripple, improve the input power factor, and provide more reliability due to the parallel path.
7- It is possible to change the UPS output voltage level, which is selected according to the battery voltage level, and it provides the ability to work with various battery voltage levels according to the required voltage level and specific use.
8- Filtering differential input noise and standard mode from the output and vice versa
In addition to the advantages of the isolating transformer, it is better to know its disadvantages in order to make a better choice in decision-making:
1- More cost for the transformer
2-Larger and heavier dimensions of UPS and rectifier-charger
3- more losses from the input to output