How to Compare Three Quotes for the Same Transformer: Normalising Before You Decide

Three Quotes, Three Different Parts

When three suppliers quote the same drawing at 1.08, 1.24 and 1.45, the instinct is to treat the lowest as best value and the highest as overpriced. In most cases the three are not the same part: they differ in core grade, insulation system, test scope, tolerance, and what is included in the price. Normalising the quotes is a 20-minute exercise that prevents an 18-month problem.

The Comparison Matrix

Twelve lines to ask every supplier for
Line	Why it changes the price
Core grade and supplier	A lower-loss grade or a different manufacturer changes both cost and loss. If the grade is unnamed, the cheapest available will be used
Wire type and insulation class	Class B to F is 8–15 %; triple insulated wire costs more than enamelled plus tape
Insulation system reference	A UL-recognised system costs more than “we build to Class F”
Tolerance on inductance	A 5 % window means grading or trimming; a 10 % window may mean none
Leakage inductance control	Interleaving or a specified construction adds labour
Test scope	100 % hipot plus inductance on every unit is different from a sample per lot
First article included?	A priced-in FAI report is not free in either quote; check whether it is inside or outside
Tooling and programme	Whether the mould, the machine programme and the fixture are charged, and who owns them
MOQ and price breaks	A quote at 1,000 pcs is not comparable with a quote at 300 pcs
Incoterm and packing	EXW and DDP differ by freight, insurance and duty, not by manufacturing cost
Currency and validity	A quote in a currency without a validity date is not a price, it is an indication
Lead time basis	From order, from material arrival, or “typical”: three very different commitments

The Four Normalisation Steps

Rewrite the drawing before you compare. If the RFQ left the core grade or tolerance open, close it now and ask all three to re-quote against the closed version. Comparing open quotes is comparing intentions.
Convert to landed cost at your door. Add freight, insurance, duty and clearing to every EXW or FOB quote, using the same forwarder and the same HS code assumption.
Add the excluded items. Tooling, FAI, packaging upgrades, and the cost of the test scope that is missing from the cheap quote.
Price the difference in test scope explicitly. If supplier A tests 100 % hipot and B samples, the difference is not margin — it is your incoming inspection. Either pay B to test, or budget the inspection yourself.

Three Patterns Worth Noticing

The cheapest quote has no test scope. Common, and usually the reason it is cheapest. On safety-critical parts this is not a saving.
The middle quote is the incumbent’s second source. A supplier trying to win a share often quotes honestly and holds it; a supplier quoting far below its own cost will find a reason to raise the price at the second order.
The expensive quote includes something you asked for and forgot. Check the FAI, the material declarations and the 100 % test before assuming a supplier is expensive.

What to Do After Choosing

Put the matrix in the purchase order as an attachment. It defines what you bought, and it converts the next conversation about a price increase into a conversation about a specific line that changed.