Disclosed is pump for circulating a liquid coolant between a heat generating device and a radiator. The pump includes a casing forming an upper chamber in which a blade assembly comprised of a plurality of blades and a permanent magnet coaxially attached to the blades is rotatably received and a lower chamber accommodating an electrical magnet comprised of silicon steel plates surrounding the permanent magnet. The permanent magnet includes first and second magnet elements coaxially aligned with and stacked to each other. The magnetic poles of the first and second magnet elements are arranged in a non-symmetric alternating manner. In other words, the magnetic poles of the first and second magnet element are angularly shifting an angle that does not correspond to 90 or 180 degrees.