Submersible pumps for wells are divided into four types according to their internal structure: water filled, oil filled, shielded, and dry. The medium filled in the motor cavity is divided into three types: water, oil, and air. The stator cavity of the shielded motor is filled with epoxy resin or plastic filling, and the external medium of the motor is well water. The cooling methods of submersible pumps with various structures are different and can be divided into four basic types. Regarding the cooling method of submersible pumps for wells, we will provide you with a detailed introduction below.
(1) Internal and external dual water cooling method for electric motors
The inner cavity of the submersible pump for wells is filled with water, and the stator iron core, stator winding, rotor iron core, and rotor winding (rotor bars and rotor end rings) are all immersed in water and directly cooled by the water inside the machine.
The heat generated by the iron loss of the motor stator, the resistance loss of the stator slot winding, and the partial resistance loss of the end winding is directly transmitted through the stator core and carried away by the well water flowing through the surface of the casing. The heat generated by the resistance loss of the rotor winding and the iron loss of the rotor is partially transmitted directly to the stator through the air gap, and then carried away by the well water outside the motor through the stator;
Another part of the heat is transferred to the water in the rotor cavity. This part of the heat, together with the heat generated by the resistance loss and mechanical loss of the stator end winding that is transferred to the water filling in the cavity, is transferred to the stator core, casing, and bearing seat through the water filling in the cavity. Finally, it is also transferred to the well water through the surface of the motor casing and bearing seat and other components for removal. The cooling effect of this electric motor's internal and external dual water cooling method is good, therefore, the temperature rise of the stator winding of the submersible pump for well use is generally low.
(2) External cooling of stator casing and direct water cooling of rotor
The main cooling method used is well shielded submersible motors. The stator of this type of motor is an independent sealed chamber, which encapsulates the stator core and winding, and is filled with epoxy resin or plastic fillers. The rotor chamber is filled with clean water.
The heat generated by the stator iron loss and stator winding resistance loss of the electric motor is directly transmitted through the stator iron core or cavity filling material, and carried away by the well water flowing through the surface of the casing through the casing. The heat generated by the resistance loss of the rotor winding and the iron loss of the rotor is partially transmitted directly to the stator through the water in the air gap and the shielding sleeve, and then carried away by the well water outside the motor through the stator
The other part is transferred to the water filled in the rotor cavity, and this part of the heat, together with the heat generated by mechanical losses, is transferred to the stator core, housing, and bearing seat through the water filled in the cavity. Finally, it is also carried away by the surface of the motor housing and bearing seat to the well water outside the motor.
(3) Internal oil cooling and external water cooling methods
The oil filled deep well pump adopts this cooling method. The internal organs of an oil filled motor are filled with insulating lubricating oil, and its stator core, stator winding, rotor core, and rotor winding (rotor bars and rotor end rings) are all immersed in oil. The heat generated by the iron loss of the motor stator, the resistance loss of the stator slot winding, and the partial resistance loss of the end winding is directly transmitted through the stator core and carried away by the well water flowing through the surface of the casing. The heat generated by the resistance loss of the rotor winding and the iron loss of the rotor is partially transmitted directly to the stator through the oil in the air gap, and then transmitted to the stator through the casing
Take away the well water outside the electric motor; The other part is transferred to the slurry filled in the rotor cavity, and this part of the heat, together with the heat generated by the resistance loss and mechanical loss of the stator end winding transferred to the oil in the cavity, is transferred to the stator core, casing, and bearing seat through the oil filled in the cavity. Finally, it is also transferred to the well water outside the motor through the surface of the motor casing and bearing seat and other components.
(4) Internal air cooling and external water cooling methods
The main cooling method used is the dry submersible pump for wells. The interior of a dry-type motor is filled with air, and the heat dissipation of its stator winding end and rotor mainly relies on the air inside the machine. The iron loss of the motor stator and the winding of the stator slot are carried away by the well water on the surface of the casing.
The heat generated by the resistance loss of the rotor winding and the loss of the rotor iron is partially transmitted directly to the stator iron core through the air gap, and then carried away by the well water outside the motor through the casing; The other part is transferred to the air inside the machine, and this part of the heat, together with the heat generated by the resistance loss and mechanical loss of the stator end winding transferred to the air, is transferred to the stator core, casing, and bearing seat through the flowing air inside the machine,
Finally, it is also carried away by the well water outside the motor through the surfaces of components such as the motor casing and bearing seat. Due to the poor thermal conductivity and small heat capacity of air, the cooling conditions for the stator winding and rotor winding of submersible motors are poor, resulting in relatively high temperature rise.
