Views: 95 Author: Site Editor Publish Time: 2023-05-26 Origin: Site
The magnet and impeller of the brushless DC magnetic drive pump are moulded into one piece to form the rotor of the motor. The rotor has a direct injection moulded sleeve in the middle and is fixed in the housing by a high performance ceramic shaft. The torque of the motor is generated by energising the coil on the silicon steel sheet (stator) to produce a magnetic field that drives the permanent magnet (rotor). The magnets are magnetised in n (n being an even number) steps so that the magnet parts form a complete coupled magnetic system with each other. The magnetic energy of the system is at its lowest when the magnetic poles of the stator coil are opposite to the magnetic poles of the magnet, i.e. the displacement angle between the two poles Φ=0. The magnetic energy of the system is at its highest when the poles are rotated to the same pole, i.e. the displacement angle between the two poles Φ=2π/n. When the external force is removed, the magnetic force will return the magnet to its lowest magnetic energy state as the poles of the magnetic system repel each other. The magnet then generates movement and drives the magnetic rotor to rotate.
Brushless DC pumps are electronically commutated without the use of carbon brushes. Both the magnet rotor and the stator silicon steel sheet have a multi-stage magnetic field, which automatically changes the magnetic pole direction when the magnet rotor rotates at an angle relative to the stator, so that the rotor always maintains the same level of repulsion, resulting in a high speed and efficiency of the brushless DC magnetic isolation pump.
The stator and rotor of the magnetically isolated pump are completely isolated, completely avoiding the liquid leakage problems that exist with traditional motorised brushless DC pumps. It can also be used completely submerged and is completely waterproof, effectively improving the life and performance of the pump.
The brushless DC water pump (magnetic isolation pump) consists of the pump body (isolated parts), motor stator, shaft, bearings and rotor water lobe (magnet and impeller).
Magnet (NdFeB permanent magnet)
Permanent magnets made of rare-earth permanent magnet material have a wide working temperature range (-45-400°C), high coercivity and good anisotropy in the direction of the magnetic field, so that demagnetisation does not occur when the same poles are close to each other.
Isolation parts
When metal isolators are used, the isolators are in a sinusoidal alternating magnetic field, which induces an eddy current in the cross section perpendicular to the direction of the magnetic lines of force and converts it into heat. The expression for the eddy current is: where Pe - eddy current; K - constant; n - rated speed of the pump; T - magnetic transmission torque; F - pressure in the isolation sleeve; D - internal diameter of the isolation sleeve; a material's resistivity; - tensile strength of the material. When the pump is designed, n and T are given by the working conditions, to reduce the eddy current can only be considered from F and D, etc. The selection of high resistivity, high strength non-metallic materials for the isolation sleeve is very effective in reducing eddy currents.