IS vs IEC Transformer Tolerances
When evaluating a transformer, guaranteed values and specified tolerances are important during technical and commercial review.
Total Losses
IS 2026 and IEC 60076 both allow a tolerance of plus 10 percent.
Individual Loss Component
IS 2026 and IEC 60076 both allow plus 15 percent, subject to the applicable total loss limit.
Impedance at Principal Tap
For impedance of 10 percent or higher, both standards specify plus or minus 7 point 5 percent.
For impedance below 10 percent, both standards specify plus or minus 10 percent.
No Load Current
Both IS 2026 and IEC 60076 allow a plus 30 percent tolerance.
For many basic transformer tolerances, IS and IEC requirements are closely aligned.
However, purchasers can specify tighter contractual tolerances than the standard requirements.
When reviewing a transformer specification, check the guaranteed values, tolerances, test methods, and acceptance criteria.
The standard provides the technical framework, while the purchase specification defines the specific contractual requirements.