Glossary
Terms used on this site, defined.
- Armature
- The rotating part of a brushed DC or universal motor: a laminated core on a shaft carrying the winding, with a commutator that connects the coils to the brushes.
- Commutator
- A ring of insulated copper bars on the armature shaft. Brushes ride on its turned surface; the winding ends are welded to its tangs (hooks). Runout and surface finish of the commutator largely determine brush life.
- Commutator runout
- The radial deviation of the commutator surface from a true circle about the shaft axis, measured in micrometres. Excess runout causes brush bounce, sparking and premature brush wear; it is controlled at the turning station.
- FAT / SAT
- Factory Acceptance Test: the machine is run on the customer's parts at the builder's plant before shipment. Site Acceptance Test: the same checks repeated after installation at the customer's site. Both are normally recorded on video and signed off.
- Flyer winding
- A winding method where a rotating arm (flyer) lays wire around a stationary armature into the slots defined by forming tools, then hooks the wire on a commutator tang before indexing. Used for most brushed DC and universal motor armatures.
- Slot wedge
- A strip of insulating material driven into the slot opening after winding to hold the coils in place against centrifugal force and protect them during turning and handling.
- Surge (inter-turn) test
- An impulse voltage is applied to a coil and the decaying waveform is compared with a reference. A shorted turn or damaged insulation changes the waveform, so the test detects winding faults that a resistance measurement cannot.