grundfos data booklet

3SP A, SPSubmersible motorsOvertemperature protectionProtecting the motor against too high motortemperature is the simplest and cheapest way ofavoiding that the motor life is reduced.Accessories for protection against overtemperatureare available for both Grundfos MS and MMSsubmersible motors. When the temperature becomestoo high, the protection device will cut out, anddamage to the pump and motor will be avoided.MSThe Grundfos MS submersible motors, except MS 402,are available with built-in Tempcon temperature sensorfor protection against overtemperature. By means ofthis sensor it is possible to read out and/or monitor themotor temperature via an MP 204 motor protector.MMSThe Grundfos MMS submersible motors are notavailable with built-in Tempcon temperature sensor.For these motors, we offer Pt100 and Pt1000 sensorsfor temperature monitoring. Together with either anMP 204 motor protector, a PR 5714 relay or a CU 220control unit, the sensor ensures that the operatingconditions are not exceeded.Protection against upthrustIn case of a very low counter pressure in connectionwith start-up, there is a risk that the entire chamberstack may rise. This is called upthrust. Upthrust maydamage both pump and motor. Therefore, bothGrundfos pumps and motors are protected againstupthrust as standard, preventing upthrust fromoccurring in the critical start-up phase. The protectionconsists of either a built-in stop ring or hydraulicbalancing.Built-in cooling chambersIn all Grundfos MS submersible motors, an efficientcooling is ensured by cooling chambers at the top andat the bottom of the motor and by an internalcirculation of motor liquid. See fig. 11. As long as therequired flow velocity past the motor is maintained(see section Operating conditions, page 4), cooling ofthe motor will be efficient.TM00 5698 0996Fig. 11 MS 400010