Test 19: Dielectric dissipation factor (applicable to enamelled wire and bunched wire)

Test 19: Dielectric dissipation factor (applicable to enamelled wire and bunched wire), IEC60815-5:2008
1 Principle 
A piece of wire is treated as a capacitor whose coating forms the dielectric and whose conductor acts as one and a conducting medium as the second electrode. This capacitor is connected into a circuit, which operates at the required frequency and which is suitable for measurement of the capacitive and resistive components from which the dielectric dissipation factor is obtained.

2 Equipment 
The following equipment shall be used:
– impedance meter, which shall operate at the frequency specified in the relevant standard and which shall provide a precision of ±1 % based on capacitance through the capacitance range required by the specimen at this frequency;
– frequency generator, which shall have a sinusoidal voltage output with a frequency specified in the relevant standard;
– test method A:
metal bath according to Figure 9, which shall contain any suitable liquid metal (alloy) and which shall have a heating system that controls the temperature to ±1 °C;
– test method B:
• two metal blocks with a heating system that controls the temperature to ±1 °C;
• conducting suspension.

3 Specimen 
3.1 Specimen for a metal bath electrode
A straight piece of wire shall be bent into a U-shape to be lowered into the metal bath according to Figure 9.
3.2 Specimen for a conductive suspension electrode
3.2.1 Enamelled round wire with a nominal conductor diameter up to and including 0,100 mm
A straight piece of wire (100 ± 5) mm in length shall be wound around a straight piece of bare copper wire of 1 mm to 2 mm diameter and subsequently coated with a conductive suspension, for example by brushing a layer of an aqueous graphite dispersion on the specimen, which shall then be dried, for example, for 30 min at 100 °C in an oven with forced air circulation.
3.2.2 Enamelled round wire with a nominal conductor diameter over 0,100 mm and enamelled rectangular wire
A straight piece of wire about 150 mm in length shall be coated with a conductive suspension, for example, by brushing a layer of an aqueous graphite dispersion on the wire. The length of this layer shall be (100 ± 5) mm. The specimen shall be dried, for example, for 30 min at 100 °C in an oven with forced air circulation.

4 Procedure 
Test method A: The specimen according to 3.1 shall be lowered into the metal bath according to Figure 9.
Test method B: The specimen according to 3.2 shall be placed between the two metal blocks. The specimen shall be connected to the impedance meter and shall be allowed to reach the specified test temperature. Thereafter, the dielectric dissipation factor shall be read directly from the impedance meter.

5 Result 
One specimen shall be tested. The dielectric dissipation factor, the test frequency and the test temperature shall be reported.