Method and apparatus for controlling heat energy of a bonding transformer

DETAILED DESCRIPTION Briefly, in accordance with the principles of the present invention, an improved method and apparatus is provided for controlling the amount of heat energy supplied by a bonding transformer to coil windings, such as armature or stator windings, or the like.
The heat energy is controlled to heat the coil windings to a predetermined temperature level in order that the bonding coat surrounding the wires of the coil windings melts and fuses the windings into an integral mass.
This is accomplished in the present invention by taking advantage of the fact that as the temperature of the coil windings being heated increases, its resistance increases, and for a preset voltage level in the bonding transformer, the current will decrease proportionately to the increasing resistance.
The control arrangement of the present invention employs a sensing coil to sense and continuously monitor the changing current in the secondary windings of the bonding transformer as a function of the changing temperature and resistance of the coil windings being heated, while maintaining the voltage level in the secondary windings of the transformer substantially constant.
The sensing coil produces an AC voltage signal proportional to the sensed current, and this voltage signal is rectified to DC and supplied to a comparator which is preset with a predetermined reference voltage indicative of the desired temperature level for performing an acceptable fusing operation.
The comparator electronically compares the monitored DC voltage signal to the preset reference voltage, and when they are equal, the comparator actuates an on-off logic control to turn off the bonding transformer.
As will be understood, as the coil windings are heated by the bonding transformer, the temperature of the windings increases, and therefore, the resistance of the windings also increases.
As a result, for a preset voltage in the secondary windings of the bonding transformer, the current sensed by the sensing coil decreases proportionately to the increasing resistance, and the voltage signal produced by the sensing coil also decreases proportionately and is sent to the comparator