My terminal connections are loosening and heating up, what should I do?
A loose terminal creates contact resistance; since the loss is P = I² × R, at 30 A a contact resistance of only 5 milliohms produces 4.5 W of heat. This heat expands the connection, loosens it further and accelerates the process. The solution is the right lug, the right tightening and re-tightening after the first run.
A hot terminal is almost always a mechanical problem, not an electrical one. Common causes:
- Tinned stranded end: Solder flows over time (cold flow), the pressure decreases and the resistance rises. On stranded cable use a ferrule instead of solder.
- Insufficient cross section: If the cable is already heating up the terminal heats up too. Choose a cross section that will carry 15 A continuous for the KS250 and 30 A for the PT500, and increase it on long runs according to the voltage drop.
- Two cables under one screw: The thinner one works loose. Connect a single conductor to each terminal, and if distribution is needed use a separate busbar.
- Vibration: In vehicle and field applications clamp the cable 10–15 cm behind the terminal so that no mechanical load is placed on the connection point.
Commissioning discipline: tighten the connections, run the system at full load for a few cycles, wait for it to cool and re-tighten all power terminals. Then check once more within the first week. A terminal that has darkened, oxidised or melted out of shape cannot be saved by cleaning; the cable end must be cut and re-terminated and the damaged terminal must be replaced.
The full topic: Locked rotor and thermal protection