A buck-boost transformer IS an insulating type transformer when it is shipped from the factory. When it is connected at the job site, a lead wire on the primary is connected to a lead wire on the secondary - thereby changing the transformer's electrical characteristics to those of an autotransformer. When a primary lead wire and secondary lead wire of a buck-boost transformer are connected together electrically, in a recommended voltage bucking or boosting connection, the transformer is in all respects, an autotransformer. However, if the interconnection between the primary and secondary winding is not made, then the unit is an insulating type transformer. Electrical and electronic equipment is designed to operate on standard supply voltage.
Many applications exist where supply voltages are constantly above or below normal.
The unit is connected as an insulating transformer and the nameplate KVA rating is the transformer's capacity. The output voltage is a function of the input voltage. If the input voltage varies, then the output voltage will also vary by the same percentage. No, there are no restrictions. Since the transformer has been autoconnected in such a fashion that the 22V secondary voltage is added to the 208V primary voltage, it produces 230V output.