THERMAL LIFE OF ENAMELLED WIRES

Studies have been carried out about classification of the electrical machines operating temperature as to the thermal endurance of the windings. The tests have been based on an extrapolated theram life of about 20.000 working hours at the maximum working temperatures for each individual thermal class. The I.E.C. published a recommendation (N. 172) in 1966 originated from the AIEE 57 method, on which the DIN 46453 - sec. 2 the I.EC. 55-1 and 2 the U.T.E. NF C 26-310 standards are based. Diagram A shows the thermal life of EMTEL’s best known enamelled wires.

Diagram A

ELONGATION BEFORE BREAKAGE

A substantial % elongation before breakage, together with a high yield point is quite important in the thin diameters range, since it prevents the wires from breaking when being wound at very high speeds. Diagram B shows a comparison between the minimum requirements according to European Standards and he average values of EMTEL’s production.

Diagram B

APTITUDE TO SOLDERABILITY

Our enamel wires type EMTSOLD, EMTYLON, EMTBOND ve EMTPOL up to diameter 0.30 mm, may be soldered by dipping their ends in a melted lead and tin alloy bath. Thus doing the enamel undergoes sublimation (without any charbon residues) resulting in a perfect adhesion of the lead-tin alloy to the copper wire. Giving a 2 second dipping period, diagram C shows which are the solderability temperatures of the above mentioned enamelled wires, according, to the copper wire diameter.

Diagram C

WINDING APTITUDE

A very soft wire allows higher working speeds and reduces winding clearances, thus saving about 1-2% of total amount of wire. Hence a lower enamelled wire total weight being its properties unchanged specifications. Diagram D shows spring back degree according to I.E.C. standards specifications and avarage values of EMTEL’s production.

Diagram D

MAXIMUM WINDING TENSION

The unwinding of the wire while still on the spool, must be carried out properly, in order not to cause such draw backs as sketchings (resulting in reduced cross section and hardening of the wire) and breakages. Winding and unwinding tensions are of paramount importance. They must be constant during the entire manufacturing processes and remain within the security limits as specified side (Table) Wire tension measurements are usually performed by means of tensiometers which feature immediate tension readings.

Table