eeet-241/2-February/2-19_Notes.md

Voltage Regulation

VR(%) ={E_{NL}-E_{FL}\over E_{FL}}\where\ E_{NL}=V_s(no\ load)\ E_{FL}=V_s(Full\ rated\ load)\ Z_p=\sqrt{R_p^2+X_p^2}\ E_{FL}=I_{n_s}\times Z_{FL}

Unrelated: Brown-outs are because there’s less power through an incandescent bulb, so the color changes to brown.

Construction of a Power Transformer

Core is something metal, probably iron. This keeps I_m low.

Windings are kept close together, to keep X_f low, which keeps voltage regulation high.

Transformer Taps

This changes the connection point to get the right voltage.

Some are motorized, these are utility values. Others are automatic, and based on the secondary voltage. They “tap” the voltage in one direction or the other.

Cooling methods

• Dry
  • non-vented (“AA”)
  • vented (“AFA”)
• Wet
  • Oil convection (“OA”)
    • think water cooling, but no pump
  • Fans connected to the “radiator” (“FA”)

Hot spot temperatures

Given 40^\circ C ambient, the following classes exist

• 55^\circ C (wet)
• 65^\circ C (wet)
• 105^\circ C
• 115^\circ C (dry)
• 130^\circ C
• 150^\circ C (dry)
• 155^\circ C
• 180^\circ C
• special cases

Some places run them “cold”, which lets them run longer. Utilities run them “hot”, which replaces them faster, but its cheaper.