Abstract: A boiling type cooling device for cooling power semiconductors includes an evaporator containing an aqueous solution of ethylene glycol as a cooling medium, a condenser; and a vapor and liquid return pipe. According to a first aspect, the lowest portion of the condensor is at a level higher than the top surface of the cooling medium in the evaporator, the bottom surfaces of the condensor being tilted downward toward the top end of the liquid return pipe. According to another aspect, a pump is provided in the liquid return pipe for driving cooling medium to the evaporator. According to still other aspects, the liquid return pipe is covered with a heat insulating material, or a rubber string extends centrally therewithin. A deaeration device for the aqueous solution of ethylene glycol includes two separate deaeration baths and a mixing bath.

Abstract: The invention is a chopper control for electric cars. In the control device, the currents of the armatures A1 and A2 of electric car driving shunt motors connected to a power source L are controlled by first chopper devices CH1 and CH2, the currents, in the forward direction, the field coils SF1 and SF2 of the shunt motors are controlled by a second chopper device FCH1, and the currents, in the reverse direction, of the field coils are controlled by a third chopper coil FCH2.