The parameter ‘D’ is most often used as a measurement of the losses in a capacitor. It is analogous to Q for a transformer winding.

For this equivalent circuit the Dissipation Factor D is defined as:

For a given capacitance, the lower the equivalent series resistance, the lower is the value of the dissipation factor or tand, i.e. the 'better' the capacitor.

Where Used

The dissipation factor test would normally be used for capacitors of all types. A D factor test will help to determine that the capacitor has been manufactured correctly.

Measurement Conditions

To measure Dissipation Factor, the tester applies an ac voltage across the selected winding, and measures the voltage across and the current through the winding. Using harmonic analysis, the measured voltage is divided by the current to obtain a complex impedance from which the Dissipation Factor is obtained.

Choosing the Test Signal

For optimum accuracy and performance, use the test conditions chosen for capacitance in a later section of this chapter.

The test conditions can also be determined automatically by the AT3600 according to this table:

Note that a ‘fixed’ signal cannot be used with an ‘Auto’ frequency.