Canned motor
The canned motor is an electric motor in which the rotor and stator are separated by a can. The can is located in the air gap between the stator and rotor of the motor, hence the name. It enables an absolutely hermetic sealing of the rotating parts against the stationary parts and the environment, and usually requires a rotor without brushes, so that this type of construction is mainly used in three-phase asynchronous machines with a power of up to approx. 2 kW. In order to avoid large losses due to induced eddy currents in the can, it must be made of a material that has a low electrical conductivity. Canned motors are used in liquid ring vacuum pumps , compressors , displacement pumps and agitators , and are also used to convey solid-free, aggressive liquid media and poisonous gases in pumps and blowers in order to prevent contact between the medium and the environment.
commitment
The canned motor is often to drive pumps used and has the advantage that the pump and motor in one unit without the need for wave or mechanical seal can be built, which also reduces space requirements.
Heating pumps of this type are referred to as wet rotor , referred to as the conveying medium (heating water) flows around the rotor inside of the can, which therefore runs wet , while the stator is in the dry located. A disadvantage of this design is the lower efficiency due to friction losses with the liquid.
This type of drive is also widespread in the chemical and petrochemical industries. The reason, in turn, is the safe separation of critical media and the environment by avoiding the need to remove moving parts such as B. having to seal a drive shaft against stationary such as the pump housing.
Due to the special motor design, canned motor pumps are usually more expensive than magnetic coupling pumps .