BAFFLE 1056087 - Caterpillar

speed controller for the fan is part of an assembly that also consists of the control panel and the main control module.The speed controller for the fan regulates the amount of voltage that is supplied to the blower motor. This controller operates in a linear mode on the ground side of the blower motor. The speed controller for the fan also provides thermal protection in the event of a short circuit. This protection is also provided for a stalled motor or any other condition which would cause excessive temperature in the heat sink. The limit of output current is proportional to the sensed output voltage which causes the current to feedback in the event of a stalled motor or a short circuit to Vbatt. Output faults will cause the temperature in the heat sink to rise. Insufficient airflow also causes the temperature in the heat sink to rise. Thermal protection is a two-stage process. When the temperature in the heat sink is greater than approximately 70°C, thermal protection causes the output to attempt the maximum output voltage. If the temperature in the heat sink continues to rise above approximately 105°C, the output will turn off. The output will turn on when the temperature in the heat sink lowers to approximately 70°C.