How do you calculate the core-loss risk score?

Multiply severity by 0.40, occurrence by 0.35 and detection by 0.25, then add them. Scores of 6, 4 and 3 give 2.4 + 1.4 + 0.75 = 4.55.

Why weight severity highest?

A severe core-loss failure — overheating, efficiency shortfall, field return — costs far more than a frequent but minor one, so severity carries the largest 0.40 weight in the index.

What is a high core-loss risk score?

On a 1-10 rating scale the index also runs about 1-10. The 4.55 default is moderate; scores above 6-7 flag modes that warrant redesign, tighter core grade control or added test coverage.

How is this different from a standard RPN?

A classic FMEA RPN multiplies severity, occurrence and detection into a 1-1000 range. This weighted-sum keeps the score on the original scale and lets you emphasize severity explicitly instead of treating all three equally.

What raises the detection score for core loss?

Modes you cannot catch in normal QA — subtle grade mix-ups, gapping errors or lamination burrs that only show as loss at temperature — get high detection scores, which the 0.25 weight then folds into the index.

Can I use this to compare cores from different suppliers?

Yes, if you score them with the same rubric. Rate each supplier's likely core-loss occurrence and your ability to detect it, and the weighted index gives a comparable risk figure.

Transformers, Coils & Magnetics Manufacturing calculator

Core Loss Estimate Calculator

Core Loss Estimate turns three FMEA-style ratings — severity, occurrence and detection — into a single weighted risk score for excess core loss in a transformer or inductor. Quality and design engineers in magnetics use it to rank which core-loss failure modes deserve attention first, rather than treating every gauss-level or grade issue equally. Because core loss drives temperature rise and efficiency, an undetected loss problem can field-fail a transformer long after it ships. This weighting keeps hard-to-detect, high-severity modes from hiding behind low occurrence numbers.

What this calculator does

Core Loss Estimate turns three FMEA-style ratings — severity, occurrence and detection — into a single weighted risk score for excess core loss in a transformer or inductor.
Use it when core loss estimate in transformers, coils and magnetics manufacturing needs a defensible ranking against other transformers, coils and magnetics manufacturing risks for the next review.
It computes a weighted core-loss risk score using 40% severity, 35% occurrence and 25% detection.

Formula used

Core Loss Estimate risk score = severity × 0.40 + occurrence × 0.35 + detection × 0.25

Inputs explained

Severity of core-loss failure:
Occurrence likelihood of excess core loss:
Detection difficulty before shipment:

How to use the result

Use it during a magnetics FMEA or design review to prioritize core-loss failure modes and QA effort.
Scores are subjective judgments on a fixed scale; two reviewers can rate the same core-loss mode differently, so calibrate the rating rubric before comparing scores across projects.

Current U.S. benchmarks

The producer price index for copper and brass mill shapes stands at 559.593 (BLS, May 2026), up 76.8% from a year earlier. Quotes priced off last quarter's material cost miss this move. Global copper trades at $13,484 per tonne (IMF via FRED, May 2026).
The U.S. has 5,397 electrical equipment and appliances establishments employing about 369,437 workers (Census County Business Patterns, 2023).

Common questions

How do you calculate the core-loss risk score? Multiply severity by 0.40, occurrence by 0.35 and detection by 0.25, then add them. Scores of 6, 4 and 3 give 2.4 + 1.4 + 0.75 = 4.55.
Why weight severity highest? A severe core-loss failure — overheating, efficiency shortfall, field return — costs far more than a frequent but minor one, so severity carries the largest 0.40 weight in the index.
What is a high core-loss risk score? On a 1-10 rating scale the index also runs about 1-10. The 4.55 default is moderate; scores above 6-7 flag modes that warrant redesign, tighter core grade control or added test coverage.
How is this different from a standard RPN? A classic FMEA RPN multiplies severity, occurrence and detection into a 1-1000 range. This weighted-sum keeps the score on the original scale and lets you emphasize severity explicitly instead of treating all three equally.
What raises the detection score for core loss? Modes you cannot catch in normal QA — subtle grade mix-ups, gapping errors or lamination burrs that only show as loss at temperature — get high detection scores, which the 0.25 weight then folds into the index.

Last reviewed 2026-05-12.