Abstract: The electric motor is provided with an attached frequency converter for rotational speed control. The frequency converter consists of a power supply and other electronic elements. While these electronic elements are arranged as a constructive unit with the electric motor, the power supply is arranged as an individual constructive unit separated from the motor, in the form of a module. The module can be made separately from the motor and electrically connected to the motor constructive unit through a connective cable. The use of the motor is no longer dependent on cooling radiators, required for the cooling of the power supply, as only the module is now fitted with cooling radiators.

Abstract: The pump unit is provided, in particular for heating and cooling installations. The speed of the pump unit may be altered by changing the operating frequency of a frequency converter feeding the electric motor and which forms a structural unit with the pump unit. As soon as the pump unit has reached a parameter characterizing the thermal overload of the same, the frequency converter is controlled in a manner so as to reduce the speed, the reduced speed n' being greater or equal to half the normal speed n.