Views: 0 Author: Site Editor Publish Time: 2025-05-27 Origin: Site
The armature is a key component in electric motors, consisting of coils that facilitate the mutual conversion between mechanical and electrical energy. Motors can be categorized as either generators or motors; here, we focus on the motor armature.
In motors, the armature (e.g., the rotor in a DC motor) is the part that generates electromagnetic force to enable motion.
The armature consists of four main components: the armature core, armature winding, commutator, and armature shaft.
Ⅰ. The armature core serves dual functions:
As part of the main magnetic circuit
As the structural support for the armature winding: the winding is embedded in the core's slots.
Ⅱ. The armature winding performs three essential roles in a DC motor:
Forms the electrical circuit
Generates induced potential
Produces electromagnetic torque for electromechanical energy conversion
Ⅲ. The commutator, a critical component of the armature, automatically reverses current direction in the winding during rotation. This directional change:
Alters the electromagnetic force on the winding
Enables continuous motor rotation
Ⅳ. The armature shaft provides mechanical support for:
✓The armature winding
✓The brushe
Its primary function is to facilitate armature rotation.
Common Armature Faults:
1. Worn Commutator
The most common armature fault is commutator wear, primarily caused by continuous friction from carbon brushes against the commutator surface. Over time, as the copper surface wears down, the insulation material between commutator segments becomes raised. This phenomenon is particularly evident in older commutators where mica insulation was used, as mica is significantly harder than copper. When the commutator reaches this advanced wear stage, it accelerates brush wear as well.
This fault can typically be rectified without requiring a complete armature rewind through two key repair processes:
✓Machining (turning down) the commutator's brush contact surface to remove damaged material
✓Precision undercutting of the insulation between commutator segments.
2. Armature Burnout
Another common fault is armature burnout, which can result from various causes, including:
Overloading
Insufficient cooling/poor airflow
Voltage regulator failure
Motor stalling
Insulation breakdown
Ground faults (earthing issues)
A burnt-out armature typically requires complete rewinding.
Prior to the development of resin-insulated wire, copper conductors were insulated using double-cotton covering (DCC) - a process where each wire was wrapped with thin cotton strands. This insulation method becomes vulnerable over time due to:
Thermal cycling: Repeated expansion and contraction from heating/cooling cycles
Mechanical stress: Centrifugal forces during rotation
These factors gradually degrade the insulation, potentially causing inter-turn short circuits. When a short circuit occurs, the affected loop exhibits minimal resistance (limited to a single turn's resistance). This results in excessive current flow through the shorted turn, generating intense localized heating.
The process creates a thermal runaway effect:
Increased heat → More insulation breakdown → Additional shorts → Further heating → Ultimately resulting in complete winding burnout.
3. Grounding Fault
A grounding fault occurs when winding insulation fails, creating an unintended electrical connection between the armature winding and its metal core.
Failure Mechanism:
The armature windings are electrically insulated from the metal core
The core typically connects to the battery's negative terminal through:
a) The dynamo housing (standard configuration), or
b) A dedicated ground wire (insulated return system)
Primary Causes of Insulation Failure:
Thermal degradation from chronic overheating
Mechanical fatigue at slot edges caused by:
Continuous thermal cycling (expansion/contraction)
Centrifugal forces during rotationVibration-induced wear
Conclusion
Mortors are essential work equipment, with the armature serving as their critical operational component. When observing any of these warning signs discussed, immediate inspection is recommended to ensure the normal operation of the vehicle. For more information about solutions of armature faultss, please contact us.
