1. Bad contact (loose connection)
2. Overload
3. Unbalance
In addition to this,
1)Loose connection, 2)overload
3) crimping of lugs not properly.(if the provided)
4) routine of maintenance is not done. Finally, Aluminium cannot connect direct to breaker. Use bi-metal cable lug. After using different conductors aluminum tends to compress, heat and vibration goes loose. Infrared heat check on connections when preventative maintenance are done helps to eliminate such situations.
