Amrest manufactures Indoor dry type resin cast and outdoor oil cooled (single and three phase type) Voltage Transformer with metering, protection purpose. Amrest also manufactures of three phase residual voltage transformer, the standard value of the secondary voltage in PT is 110V or 110/3 the value of rated burden is 10VA to 500VA at a power factor of 0.8 lagging. The standard accuracy of class for measuring PT is 0.1, 0.2, 0.5, 1.0, or 3. The standard accuracy of class for protective PT is 3P and 6P, the standard accuracy of class for three phase residual voltage transformer is 5PR and 6PR, The voltage factor to be specified are different.