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June, 2018


IF PERFORMANCE COUNTS,


IF RELIABILITY COUNTS,


INTERCONNECTS COUNTS A LOT.


THEN YOUR CHOICE OF


Maintaining a seamless, uninterrupted signal is the objective for any electronic system. Regardless of how elegantly designed or sophisticated the individual components might be, continuity and reliability will only be as good as the interconnects that link them. Machined pin receptacles from Mill-Max can make the difference between a product that only performs adequately and an exceptional product that lasts.


To learn more, download our new white paper at www.mill-max.com/design.


Understanding the Basics of Voice Coil Actuators


By James Mitchell, VP of Engineering, H2W Technologies, Inc. A


voice coil actuator, also known as a non-commutated DC lin- ear actuator, is a type of direct


drive linear motor. The name “voice coil” comes from one its first applications: vibrating the paper cone of a loud- speaker. These devices are commonly used for a wide range of applications, in- cluding moving much larg- er masses than themselves. The actuator consists


of a permanent magnetic field assembly (permanent magnets and ferrous steel) and a coil assembly. The current flowing through the coil assembly interacts with the permanent mag- netic field and generates a force vector perpendicular to the direction of the cur- rent. The force vector can be reversed by changing the polarity of current flowing through the coil. A non-commutated DC linear


that moves in and out of the magnet assembly, the moving magnet style utilizes a permanent magnetic field assembly “piston” moving inside a


Typical voice coil actuator, consisting of a coil-wound bobbin that moves in and out of a fixed magnetic field assembly.


actuator, typically referred to as a voice coil, is capable of a displace- ment of up to 5 in. (12.7 cm), where- as most actuators have displace- ments up to 2 in. (5.1 cm). Voice coils come in a range of


sizes, from devices that generate a few ounces of force, to others that generate several hundred pounds. Voice coil actuators can move bidirec- tionally, have a constant force over the stroke, and can be used for either open-loop applications or closed-loop position or force applications. A voice coil actuator generates a


force based on an interaction of cur- rent carrying conductors in a perma- nent magnetic field. The force gener- ated by the voice coil is proportional to the cross product of the current flowing through the coil and the mag- netic flux in the permanent magnetic field, as dictated by Lorentz’ force equation: F = B x I. F is the force in pounds or newtons, B is the flux den- sity measured in teslas, and I is the current in amps. The force generated is relatively


constant throughout the stroke of the actuator, with minor decreases in force at the beginning and end of the stroke. Either the coil assembly or permanent magnetic field assembly can be used as the moving member in a voice coil actuator.


Types of Voice Coil Actuators Voice coil actuators come in a va-


Maximum Reliability. MillMaxMfg MillMaxMfg MILL-MAX MFG. CORP. Mill-Max Mfg. Corp. • 190 PINE HOLLOW ROAD OYSTER BAY, NY 11771 • (516) 922-6000


riety of packages. The standard type, which most people are familiar with, are moving coil actuators. These in- volve a coil wound around a bobbin, which can be made from many non- magnetic materials, which moves in and out of a permanent magnetic field assembly consisting of a steel housing with a concentric permanent magnet assembly in the middle. Another common type of actua-


tor is the moving magnet design, where the coil is fixed and the mag- net assembly moves. This construc- tion prevents moving leads during operation. The package operates sim- ilarly, but instead of an exposed coil


cylindrical coil tube. This style often comes with the permanent field as- sembly attached to a shaft, and end caps containing bearings. This style is most commonly supplied with an integrated bearing system. There are variations of both


common actuator designs that allow for unique geometry and the integra- tion of voice coils into many applica- tions. Customization options include: large radial clearances so that the


The voice coil actuator’s name comes from one of its first applications:


vibrating the paper cone of a loudspeaker.


voice coil can be used in limited rota- tion; designs that intentionally oper- ate the voice coil motor in an arc (often referred to as a rotary voice coil actuator); low-outgassing materi- als for use in vacuum environments; and the integration of feedback de- vices for closed-loop control. Voice coil actuators are often used in focus- ing applications, oscillatory systems, mirror tilting, and miniature posi- tion control. H2W Technologies designs and


manufactures linear and rotary mo- tion products that are used in the motion control industry. The compa- ny’s complete line of linear electric motors includes single- and dual-axis linear steppers, DC brush and brush- less linear motors, voice coil actua- tors, and AC induction motors. Also offered is a complete line of ball screw, lead screw and belt-driven po- sitioning stages. Other motion control products


include limited-angle torque motors for compact, limited-angular excur- sion rotary servo applications, three- phase brushless rotary servo motors with matching digital servo amplifiers and permanent magnet linear brakes


for fail-safe, zero-power braking. Contact: H2W Technologies,


Inc., 26380 Ferry Court, Santa Clarita, CA 91350 % 888-702-0540 fax: 661-251-2067 E-mail: info@h2wtech.com Web: www.h2wtech.com r


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