The adaptation of cooling systems on two DC motors at PPC Cement Company’s Dwaalboom plant by Marthinusen & Coutts has successfully eliminated the ingress of carbon. The electric motors at the plant were failing due to carbon ingress. The original DC motors in the plant had a closed circuit cooling system with air flow over the commutator first and then through the motors. This is where the ingress of carbon originated. In the past, PPC has changed cooling circuits on its DC motors as a result of carbon ingress problems.

The modified cooling circuit feeds cooling air into the drive end of the motor, through the motor, onto the commutator and then to the atmosphere. Marthinusen & Coutts fitted external fans to both motors to facilitate this type of cooling system, where the cooling is essentially reversed and opened. The fans were fitted to feed cooling air to the drive end of the motor. The outlet of the commutator was fitted with an exhaust attachment and the inlet to the fan has a filter to eliminate the ingress of dust and dirt.