Symptoms of a bad armature.

AIP shares with you the"Symptoms of a bad armature".

August 26, 2023

Symptoms of a bad armature

The armature is a part with coils in the motor, which plays a key role in the mutual conversion of mechanical energy and electrical energy in the motor. Motors are divided into generators and motors. Today we mainly introduce the motor armature. For motors, the Armature is a part with coils in the motor, which plays a key role in the mutual conversion of mechanical energy and electrical energy in the motor. Motors are divided into generators and motors. Today we mainly introduce the motor armature. For motors, the armature is a component that generates electromagnetic force, such as the rotor in a DC motor.

Motor structure

The armature includes an armature core, armature winding, commutator, and armature shaft. Ⅰ.The armature core is not only a part of the main magnetic circuit but also the supporting part of the armature winding, and the armature winding is embedded in the slot of the armature core; Ⅱ.The armature winding is the circuit part of the DC motor, which is also the induced potential, generating Electromagnetic torque is the part of electromechanical energy conversion; Ⅲ.The commutator is an important part of the armature, which automatically changes the direction of the current in the coil when the motor rotates so that the force on the coil changes so that the motor can continue to rotate a component. Ⅳ. The function of the armature shaft is to support the armature winding and the armature brush and to enable the armature to rotate.

Armature rotor structure

Armature common faults

1. Worn commutator

The most common fault with armatures is worn commutators, caused by the friction of carbon brushes against the commutator surface. Over time the insulation between the commutator segments becomes proud as the copper of the commutator surface wears away. This is especially so with older commutators as the insulation that was used to separate the commutator segments was mica, which is harder than copper. When the commutator has worn down to this point it will also quickly wear down the brushes.

This fault can usually be repaired without rewinding the armature by turning the commutator brush surface down below the damage and then undercutting the insulation between the commutator segments.

2. Armature burnt out

Another common fault is for the armature to burn out. This can be caused by a number of different problems such as overloading, poor airflow, regulator failure, stalling, insulation breakdown, earthing, etc. If the armature has burned out then it will need to be rewound.

Before the invention of resin-covered wire, copper wire was insulated by the method of double-cotton covered, a thin strand of cotton wrapped around the wire. Over time the expansion and contraction of the copper wire through constant heating and cooling, combined with centripetal force, can cause the turns within the coils to short out. The shorted turns get hot as the voltage generated in them has only the resistance of that one turn so the current it draws can be high and that high current generates heat. This heating causes further shorts and more heating until eventually the winding itself burns out.

If too much current is demanded from the dynamo, either through a fault on the voltage regulator, too many high-power light bulbs, a fault on the battery, or a low resistance introduced to the system, then the armature can get very hot. As the armature heats up, the internal resistance of the armature goes up causing more power to be dissipated across the armature itself, generating even more heat. This can cause the solder connecting the armature coils to the commutator to melt. As the armature is spinning the solder is thrown from the armature, causing the connections between the armature coils and the commutator to be broken.

3. grounding

Earthing (grounding) is a common fault that occurs when part of the winding becomes connected to the metal core of the armature. The armature windings are insulated from the metal core and the metal core is often connected to the negative side of the battery, through the body of the dynamo (unless it is an insulated return in which the negative side of the dynamo is connected to the battery with a wire). Earthing usually occurs when insulation breaks down, usually through overheating or fatigue on the edge of a slot through constant heating, cooling, and spinning.

AIP currently has a mature motor testing program. AIP's armature tester can test items including welding resistance, bar-to-bar resistance, diagonal resistance, AC hi-pot, insulation resistance, and surge. The equipment can be maintained remotely, power-on self-inspection, simple operation, and can meet various armature electrical performance on-line or off-line tests. Insulation and other special process armatures, automatic identification of faults such as solder joints, short circuits of windings, open circuits, wrong windings, and poor welding.

AIP armature tester

You can contact us at Tel/Whatsapp: +86-13969776659 or E-mail: to learn more about armature testing details.