Connection Failures

We see connection failures at the internal lead-cable to coil-lead connections in wind generators. These tend to have prematurely failed due to overheating and resulted in blown connections. A good deal of those failures can be attributed to issues in brazing those connections. Many winding technicians are tricked into a false sense of achieving a proper connection especially when basic winding analyzer tests show the proper ohms per circuit. Consider that these connections have stout wire, possibly a #12-gauge magnet wire, just over .080” (2mm) in diameter each, and 19 wires-in-hand (wires in parallel) coming out of the stator coil groups for connection to a lead cable. It can be challenging to get every one of those 19 wires-in-hand brazed to the lead cable. The attached picture is an example of the stator coil leads that each need connected to a lead cable and brought outside the generator for termination.

Relying on one basic test from even the most advanced of our modern technologies to test this connection can give you a false sense of having achieved that 100% connection. Sure, we want to see the resistance of that circuit and certainly the circuit must flow the voltage applied or generated however, the main purpose of that connection is to carry the current. We can twist bare wires together and they can test the proper ohms. This simple type of connection can pass voltage through a no-load circuit just fine. The situation changes when the connection is under current. If one or more of the coil lead wires-in-hand are not 100% connected to the lead cable in a method that can handle the current the connection gets hotter leading to reduced reliability. Brazing is the most common method utilized to enable the full current carrying capability.