Loudspeakers were used to amplify or create a louder voice, thus the name “voice coil” stuck. Voice coil motors use similar technology to speakers, but they are designed to produce higher forces over larger distances or “strokes”. Voice coil motors do not have the commutator but uses a position sensor. These motors consist of two separate parts; the magnetic housing and the coil.
Voice coils typically consist of:
The current running through the coil creates a magnetic field, which interacts with the field established by the permanent magnet.
The voice coil works because of the force between a static magnetic field and an electric current perpendicular to the field.
The operation principle of voice coil:
Below is a schematic diagram of a current carrying wire and a magnet.
Voice Coil Motor Characteristics:
For wear resistance and good surface finish along with required magnetic properties, the shaft material is either stainless steel (hardenable stainless steel may be slightly magnetic and have a slight influence on the force characteristic, nonmagnetic stainless steel is softer and more susceptible to damage) or titanium. The magnet assembly of VM series is designed for good volumetric efficiency and useful linear stroke, these characteristics may be at the expense of some loss of linearity. High Energy Density magnets drive the material of the voice coil pot (housing) close to magnetic saturation to develop the strongest possible magnetic field.
Stanford Magnets offer custom magnets assemblies to ensure accurate guidance of the coil assembly within the magnet assembly, and to facilitate easy installation in customer applications. Custom designs can demonstrate better linearity at the expense of increased size/weight & cost.
· Coils of VCM series are normally designed to use the full depth of the pot assembly. This results in maximum mechanical work output capability but may result in a force characteristic which is not ideally suited to a given application. The portion of the coil which lies outside the airgap field dissipates power (as heat) but develops no useful force.