Motor fan control apparatus

摘要

Two motor fans are driven by two 4-pole direct current motors (1,2) respectively. Rotational speed of the two motors is controlled in three stages, namely low, intermediate, and high speed. For low speed operation the motors are connected in series with four poles; for intermediate speed operation they are connected in parallel with three poles; and for high speed operation they are connected in parallel with four poles. In another embodiment 3-pole motors are used: for low speed they are in series with two poles, for intermediate speed they are in parallel with two poles, and for high speed they are in parallel with three poles.