If the eccentricity of the commutator is not acceptable, you could end up with broken brushes and/or brush springs. It is very important to keep proper maintenance schedules to ensure the commutator stays round without run-out on the surface. Some larger DC motors may be able to be machined onsite to prevent unnecessary extraction of the motor. The segments are insulated between bars with a molding mica. The bars on a commutator must be maintained by way of machining the segmented commutator bars true. Like carbon brushes, the commutator requires maintenance from time to time. Setting the neutral can be adjusted and performed onsite when applicable. Changing loads can be difficult to get right. Keeping the brushes in a neutral position can prevent excessive arcing while under load. To do this, you need to position the adjacent brushes in an area on the commutator outside or in between the polarity reference of the armature coils being energized with voltage across the brushes. The rack or yoke component must be properly adjusted to what is called “neutral” position. A very low megohmmeter reading can notify the DC drive to shut down the power to warn of a potential to ground. A good way to prevent carbon build up is to use compressed air to help remove any lingering dust from within the motor. Carbon dust is destructive to the insulation and must be maintained by way of removing the dust within the motor to prevent low megohmmeter readings.
It is also important to keep proper, constant pressure on the brush to the commutator to deliver the full current density at the point of contact in order to alleviate premature wear on the brushes. A carbon brush survey could be of value to investigate the proper grade of brush for each of your applications. This issue can wear the commutator bars to a point of irreversible damage. When an applied load is not consistent and the motor has the wrong grade of brushes, the carbon brushes can wear out prematurely, causing carbon dust to accumulate within the motor. This is very important for brush conductivity on the commutator and the current density so the brushes can maintain a certain lubricity when contacting the commutator under load. Carbon BrushesĭC motors must be applied with the proper amount of load. This article will help you troubleshoot six of the most common DC motor issues. DC motor users in the manufacturing sector know all too well the headaches that can come along with troubleshooting issues. Though DC Motors are simple machines, proper and timely maintenance is important to lengthen the motor and facility’s lifespan.
Structure and Application of Brushless DC Motors Summary of Rotation Principle of DC Motor With a Core Slot Rotation Principle of DC Motor With a Core Slot
Rotating Speed of DC Motor And Counter-electromotive Force Reviewing the Principle of DC Motor Rotation
This structure of the DC motor enables some windings to be sequentially switched over as the rotor rotates. As the figure is self-explanatory, current from the terminal flows by dividing the group of coils into two. When a rotor coil is expanded, we will see that the coils are connected to the commutator like flower petals are to the calyx as Fig. Also, the method of winding a coil between neighboring slots is called concentrated winding, and this method has been adopted for stepping motors and brushless DC motors. This winding method is called lap winding. With a motor that has many slots, the coils are cross-coupled as Fig. For this reason, higher end motors have more slots and many coils. The greater the number of slots and coils, the smoother the rotation will be due to the reduction of torque non-uniformity (fluctuation). If there are only a small number of slots, there will be a difference in the torque generated depending on the rotational position. This is a structure that we have become familiar with through the use of motors used in models. The minimum number of slots required to allow the rotor to rotate from any angle is three. The rotor of the type of DC motor we usually see has a lamination of slotted thin steel sheets (silicon steel plates), and the coil is inserted into the core slots. Now for an examination of a motor with an iron core.