Armature, Field, Carbon Brush Life

The brushing unit of the HOST equipment is unique and careful attention needs paying to Armature, Field, Carbon Brush Life. The unit uses an armature and field assembly rather than a swap in motor and operators ask about the life of these various components, the armature, field and carbon brushes. We asked this question of our VP Manufacturing in the USA John Kwasniewcik. Also of Steve Parker who provides our engineering support in the UK. Their advice on maximising the life of armatures, fields and carbon brushes is that an armature is a wearing item and many factors determine its life.

Commutator & Carbon Brushes

New Commutator
New Commutator

The commutator is usually the part of the armature that wears out and fails. A few factors decide its life. Upkeep of the carbon brushes is most vital to longevity.

Changing carbon brushes before they wear down results in less stress on the armature by keeping the temperature of the commutator in the normal range. When carbon brushes are allowed to wear down past their normal life they bounce and do not make good contact with the commutator. This causes excessive heat build up and premature failure. Change carbon brushes in pairs and when they wear down to 8mm.

The type of carpet beings cleaned can determine commutator life. When cleaning a high or long pile carpet, the resistance between the brushes and the carpet increases slowing down the motor and causing it to draw additional amperage; this will wear out the commutator more quickly than running on a commercial low pile carpet. Another factor is Excessive downward will cause machine motor to slow and will draw more amperage, causing potential over heating.

Electricity Supply

A hidden factor that few look at is the incoming current to the machine. If the machine is designed to run on 220/240 voltage, it is not uncommon that many older residential and commercial facilities will see a voltage drop in their power lines. If voltage drops by 10% then the motor may slow down causing it to draw more amperage, causing excessive heat. This heat will not dissipate under normal run conditions.

With so many factors going into the life of an armature is the reason we do not advertise a set amount of hours for the armature. Each situation is unique and therefore difficult to predict the total hours of life.


carbon brush wear
Replace Carbon Brushes before they wear down to this level

Similarly, fields have no wear parts so they are not the same but can easily be destroyed by the armature drawing excessive amperage over time. The resulting heat will break down the varnish and cause the field to fail. The reason for the varnish is two fold.

First, it is to insulate the armature.

Secondly, it is to prevent the wires from moving and rubbing against each other when vibration occurs. Varnish breakdown would cause a direct short between the wires and instantly destroy the armature.

You will ensure a longer life for Armature, Field and Carbon Brush by keeping the machine clean, always ensuring that vents are clear to reduce heat build-up in the motor and making sure that   carbon brushes are changed before they wear down.