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"GREEN" SOLENOID SOLUTIONS
There are many definitions of what constitutes a "green" product, as well as the variable degree of "greenness" a product may exhibit. Many consider a product "green" if it provides superior or even comparable performance to an alternative product while it consumes fewer resources, uses less energy and/or generates less heat. This broad definition can easily be applied to "latching solenoid" technologies designed and manufactured by TLX Technologies LLC. In general, latching solenoids conform to the "green" definition by consuming no power, producing no heat and generating no electrical noise while holding in either the on or off position. This "green" technology can provide superior performance over constant powered solenoid actuators.
Permanent Magnet (PM) latching solenoid actuators utilize permanent magnets in conjunction with the solenoid coil to maintain position of the plunger with no current applied. The permanent magnet generates a small magnetic flux in the magnetic circuit generating an attraction of the plunger and the fixed pole piece with no power applied. When a short pulse of electrical current is applied to the coil, the resulting electromagnetic flux generated by the coil can either add to or subtract from the permanent magnet flux depending on the polarity of the applied current. In applications where the load is acting to extend the plunger away from the fixed pole, latching solenoids can maintain the extended or retracted position without consuming continuous power. In applications where there is no load to act on the plunger, a spring can be used to hold the plunger in the extended position. In either case, a pulse of current is applied to generate magnetic flux to add to the permanent magnet and move the plunger to the fixed pole piece. When the current is removed, the plunger is held in the "latched" position by the permanent magnet. Conversely, applying a reverse polarity pulse will cancel the flux of the permanent magnet allowing the load or spring to release the plunger and move to the extended position.
Residual Magnetism (RM) latching solenoid actuators operate in much the same way as PM latching actuators do, but with some unique design differences. While both type of latching actuators maintain the latched position without electrical power, Residual Magnetism latches remain latched without the use of permanent magnets. RM latching actuators offer the same benefits as PM latching actuators by consuming no power, producing no heat and generating no electrical noise while in the latched position. RM latches utilize the inherent "residual magnetism" common to all DC actuators which has been enhanced through special internal design features to provide exceptional latching force without permanent magnets. Latching the RM latch is accomplished by providing a short pulse of electrical current of either polarity to pull-in and latch the plunger to the fixed pole piece. Unlatching the actuator is accomplished by applying a pulse of lower current in the opposite polarity of what was used to latch the actuator. Unlike the PM latching actuators which can be manually latched, RM latching cannot be reset after de-latching without applying a pulse of electrical current.
Both styles of latching actuators are equally "Green" and well suited for applications where high speed actuation and long open or closed times are desired. Fig 2 illustrates the relative power consumption comparison between conventional constant current solenoids and "latching" solenoids. The response time to move the plunger is the same for both solenoids, but as the conventional solenoid is required to maintain the current (consume power) for the full on cycle, the "latching" solenoid moves with a "pulse" of current and is turned off (consuming no power) for the duration of the on cycle. Conventional solenoids are restricted to generating forces only up to a 100% duty cycle and may be subject to heat dissipation problems. The "latching" solenoid can be turned-off during most of the on cycle allowing the use of a higher current pulse to produce faster speed operation and generating higher pull force without the excessive power consumption or heat generation of a conventional solenoid. In addition, the possibility of applying a higher current to generate more force, may allow for a smaller actuator to be used for a given application and offer a potential benefit of overall cost reduction.
While latching actuators can offer performance advantages in a variety of applications, latching actuator technology may not be well suitable for use in applications where the actuator is required "fail" to a known position upon power failure. Since latching actuators need to be powered to change state, the actuator would remain in the position it was in when the power failed. If desired it is feasible to include a drive circuit with an energy storage feature in the control circuitry to allow the actuator to be positioned properly in the event of a power failure.
Both PM and RM latching actuators can be custom designed in either open frame or tubular solenoids as push, pull or bi-stable (push-pull) arrangements as well as two or three position configurations, depending on application requirements. In addition, a variety of drive circuits from a simple a diode-resistor circuit to the more complex PWM current control circuit can be used to offer the most "green" and cost effective solution your application problem.
Call or e-mail TLX Technologies, LLC for all your "Green" solenoid needs.
- Wayne Groth, TLX Sales Engineer
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Fig. 1 - Residual Magnetism
Latching Solenoid
Fig. 2 - Energy Consumption of
Latching v. Non-Latching Solenoids
Fig. 3 - Three-Position
Latching Solenoid |
