Rating Envelope Screen

Seven questions that resolve whether a configured pad-mounted unit sits inside the United States regulated distribution transformer definition, and where it lands against the current equipment standard. Answer what you know; leave the rest for drawing review. Mark the sheet, print it or save it as a PDF, and attach it to your requisition.

Project or requisition reference Screened by Date

Screening Criteria

1. Output line voltage

Is the secondary line voltage 600 V or less?

Yes, ≤ 600 V No, > 600 V Not fixed

This is the single fastest exit from the regulated definition. Above 600 V output, the rule does not reach the unit.

2. Frequency

Is the unit rated for 60 Hz operation?

Yes, 60 Hz No, 50 Hz/other Not fixed

3. Capacity

Is the rating between 10 kVA and 5000 kVA, liquid-immersed?

Yes, inside band No, outside band Not fixed

3360 kVA sits inside this band.

4. Input line voltage

Is the primary line voltage 34.5 kV or less?

Yes, ≤ 34.5 kV No, > 34.5 kV Not fixed

23 kV sits inside this limit.

5. Impedance

For a three-phase liquid-immersed unit of 750–5000 kVA, is the impedance inside 5.0 % to 7.5 %?

Yes, 5.0–7.5 % No, outside Set by study

Outside the band, the unit meets the special-impedance definition and is excluded by name.

6. Tap range

Is the range between the highest and lowest tap less than 20 % of the highest tap?

Yes, under 20 % No, ≥ 20 % Not fixed

7. Named exclusions

Is the unit free of every excluded type below?

Yes, none No, one applies Not checked

Autotransformer · drive (isolation) · grounding · machine-tool (control) · nonventilated · rectifier · regulating · sealed · special-impedance · testing · tap range 20 % or more · uninterruptible power supply · welding.

Result

Answer the questions above and the screen resolves here.

Loss Capitalisation Inputs to Send With the Enquiry

If your organisation evaluates transformers on lifetime cost rather than first cost, send these four values with the drawing. They let the winding and core design land on your economics instead of on a generic loss target.

Evaluation Strategy

The evaluated total is the purchase price plus the capitalised no-load loss plus the capitalised load loss. The lowest evaluated total is often not the lowest purchase price, which is the point of running the calculation before the award rather than after it.

Send Your Project Inputs for a Quotation ← Back to combined substation transformer

Input	Unit	What it does
No-load loss capitalisation factor (A)	currency / watt	Prices the standing core loss across the service life
Load loss capitalisation factor (B)	currency / watt	Prices the winding loss at the loading you expect
Expected loading profile	per-unit of rating	Sets how much the load loss actually matters against the core loss
Evaluation period & discount rate	years, percent	Determines how far future losses are discounted into the award decision