Baoding Jikai Power Equipment Co., Ltd.
Distribution Transformer Losses: Compare Lifetime Cost
Distribution transformer losses can change the commercial ranking of two quotations. A transformer operates for many hours after the purchase order is forgotten, so a meaningful bid comparison should include expected energy losses as well as the equipment price. The useful question is how each offered design performs under your load profile.
No-load loss and load loss are different
No-load loss occurs while the transformer is energized, even with little useful load connected. Load loss rises as current increases. For an initial estimate under comparable operating conditions, total loss can be approximated as P0 + x²Pk, where P0 is no-load loss, Pk is rated load loss and x is the fraction of rated load. Eaton explains this relationship in its power distribution application guide.
A worked example for comparing bids
The following numbers are hypothetical, not Jikai product specifications. Suppose two equally rated transformers run continuously at 50% load. Offer A has 0.80 kW no-load loss and 7.0 kW rated load loss. Offer B has 0.65 kW no-load loss and 6.6 kW rated load loss.
| Calculation | Offer A | Offer B |
|---|---|---|
| Loss at 50% load | 0.80 + 0.25 × 7.0 = 2.55 kW | 0.65 + 0.25 × 6.6 = 2.30 kW |
| Annual loss at 8,760 hours | 22,338 kWh | 20,148 kWh |
The difference is 2,190 kWh a year. At an illustrative energy rate of USD 0.10 per kWh, that represents USD 219 annually. An additional purchase cost of USD 1,000 would have a simple loss-saving payback of about 4.6 years under these assumptions. This calculation excludes financing, tariff changes, maintenance differences and auxiliary equipment.
Use the actual load profile
A factory with one daily production shift does not have the same loss pattern as a continuously loaded facility. Divide the year into representative load periods, calculate losses for each period and multiply by its hours. Add the results. Do not square an annual average load and assume that it captures substantial peaks and troughs.
Keep the assumptions visible in the bid sheet. Record energized hours, loading levels, energy price and the evaluation period. If future expansion is uncertain, run a current-load case and an expansion case so the purchasing decision does not depend on a single optimistic forecast.
What to request from the manufacturer
Ask for guaranteed no-load and load losses, the reference temperature, applicable tolerances and test documentation for the exact capacity. Check whether cooling auxiliaries introduce additional consumption. Confirm that quoted loss values belong to the proposed voltage ratio, connection group and impedance rather than a different catalog configuration.
Jikai’s S20-M.RL/S22-M.RL page publishes series-level loss information and notes that technical values vary with capacity and connection group. Use that page to identify candidate products, then request a model-specific guaranteed data sheet for your comparison.
Frequently asked questions
Does lower no-load loss always mean lower annual cost?
No. Load loss, operating hours, load profile and purchase cost all matter. A lightly loaded network and a heavily loaded industrial site can favor different designs.
Should an oversized transformer be selected to reduce load loss?
Not on that calculation alone. Capacity selection also affects no-load losses, cost, physical size and system design. Compare complete alternatives against the project’s required duty.
Discuss your project with Jikai
Review the related Jikai product specifications, then send your project requirements for a configuration-specific quotation. Include the destination country, quantity, electrical duty and relevant drawings.
