Method for insulation of coil of toroid transformers
A method of insulating a coil of a toroidal transformer includes forming an opening in an electrically insulating thermoplastic cup receiving a core with a coil for leading through terminals of the coil, arranging the core with the coil in the cup with the coil terminals led out of through the opening, covering the cup with a plastic lid which engages the cup, and temporarily fixing the cup in an irrotatable manner. The method further includes joining the cup and the lid by rotary welding by pressing the lid against the cup and rotating until the lid and the cup heat up and their material soften and become viscous due to friction, and stopping the rotation of the lid within not more than one second after softening while maintaining the pressure of the lid and the cup to join their mixed material to form a continuous electrical insulation.
1. A method for insulating at least one coil of a toroidal transformer, wherein the at least one coil arranged on a core of the toroidal transformer is externally insulated, by forming outer electrical insulation of the at least one coil arranged on the core and comprising:
forming an opening in an electrically insulating thermoplastic cup receiving the core with the at least one coil for leading through terminals of the at least one coil;
arranging the core with the at least one coil in the cup such that the terminals are led out of the cup through the opening;
covering the cup with the inserted core and at least one coil with a plastic lid which engages the cup in a form-fitting manner;
temporarily fixing the cup comprising the core and at least one coil in an irrotatable manner;
joining the cup and the lid by friction welding by pressing the lid against the cup and rotating the lid in this pressed state until the lid and the cup heat up and the lid and the cup soften and become viscous due to friction;
after softening of the lid and cup pressed together, stopping the rotation of the lid within not more than one second while maintaining the pressure of the lid and the cup;
at maintained pressure joining the lid and the cup to form a continuous electrical insulation; and
after cooling down and solidification of the materials of the joined lid and cup, removing the temporary fixing of the cup.
2. The method according to claim 1 , further comprising after forming the opening in the cup:
pressing a thermoplastic sleeve, serving for insulated leading of the coil terminals led through the opening, to an outer side of the cup with a pressure force of N+5% and coaxially aligned to the opening;
while maintaining the pressure, rotating the sleeve at a speed in a range of 450-550 rpm until the cup and the sleeve soften and become viscous due to friction;
after softening the cup and sleeve pressed together, stopping the rotation of the sleeve within not more than one second while maintaining pressure on the cup and sleeve; and
at a maintained pressure, joining the cup and the sleeve.
3. The method according to claim 2 , comprising the step of stopping the rotation of the sleeve after the joining within 0.5 second.
4. The method according to claim 1 , comprising the step of pressing the lid against the cup with a force of 20 newtons (N)+5% and rotating the lid at a speed in a range of 400-500 revolutions per minute (rpm).
5. The method according to claim 1 , comprising the step of stopping the rotation of the lid after fusion of the lid with the cup within one second.
6. The method according to claim 1 , wherein the cup and the lid are made of polyethylene or polyoxymethylene.
7. The method according to claim 2 , wherein the electrical insulation is made of polyethylene or polyoxymethylene.