Rating editor of DC motor
Mechanical power output on the motor shaft of 1. rated power PN.
2. rated voltage UN: DC voltage added on the armature under rated working condition. (example: 110V, 220V, 440V)
3. rated current IN: under rated voltage output current on the shaft rated power
Shunt excitation and armature current are included.
Rotation speed of rated speed nN: at PN, UN, IN.
4. DC motor speed is generally above 500r/min. The speed of a special DC motor can be very low (such as a few revolutions per minute) or very high (more than 3000 revolutions per minute).
Note: when the speed of the motor without speed control requirements, the maximum speed can not exceed 1.2nN.
Selection and editing of characteristic types of DC motor
(1) constant torque production machinery (TL must, and speed independent), to choose the hard characteristics of the motor, such as: metal processing, lifting machinery, etc..
(2) ventilation mechanical load, mechanical load TL is proportional to the square of the speed n. This kind of machine also chooses the hard characteristic motor to drag.
(3) constant power load (when P is constant, T is inversely proportional to n), soft characteristic motor drive should be selected. Such as: electric locomotive and so on.
Edit the direction of rotation of DC motor
There are two ways to change the direction of rotation of DC motors: :
One is the armature reverse connection, that is to keep the polarity of the terminal voltage of the excitation winding unchanged, and to reverse the motor by changing the polarity of the terminal voltage of the armature winding;
Two is the excitation winding reverse method, that is to keep the polarity of the armature winding terminal voltage unchanged, by changing the polarity of the excitation winding terminal voltage to make the motor tune. When the polarity of the voltage changes simultaneously, the rotation direction of the motor remains unchanged.
The armature reverse connection is used to realize positive and negative rotation of the separately excited and shunt excited DC motor. It is not suitable for the excitation and winding shunt motor to adopt the reverse method of excitation winding to realize the positive and negative rotation. The reason is that the number of windings is larger and the inductance is larger. When the excitation winding back, the excitation winding will produce large electromotive force. The insulation which will damage the knife and excitation winding.
DC motor with excitation winding should cause reverse method to achieve positive is because the DC motor's armature voltage is higher, and the excitation winding voltage is very low, easy to reverse, often used by motor vehicles.