ELECTRICAL & ELECTRONICS: ACTUATORS oemoffhighway.com/21563427
Electric Actuator Advancements Expand Options for Replacing Hydraulic Cylinders Electric actuators can provide a lower total cost of ownership compared to hydraulic cylinders, as well as increased control and precision capabilities. contributed by Travis Gilmer, Product Line Specialist – Industrial Linear Actuators, Thomson Industries, Inc.
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s electric actuators advance in load handling, durability and intelligence, their potential as hydraulic cylinder replacements continues to grow. Depending on your initial objectives for specifying hydraulic cylinders, there are an increasing number of electric alternatives that might meet—or even exceed—those specifications. If you specify hydraulic actuators, taking some time to evaluate the widening range of electric options available for your next application could pay off handsomely.
Increased force capabilities Until a few years ago, a machine designer building an application such as a signage boom truck would likely have used hydraulic cylinders. Doing so requires an oil reservoir, a system of tubing to bring the fluid from the reservoir to the cylinder, and a set of power cables running throughout the boom. Leakage is a possibility at any point, and maintenance demands are high. A modern electric option for such applications is a hybrid actuator that Figure 1: This H-Track electrohydraulic linear actuator from Thomson can handle up to 4,800 lbs. (21 kN) of force in a clean, compact enclosure that also has shock handling capabilities comparable to a hydraulic system.
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integrates the lifting capability of a hydraulic system with the cleanliness, compactness and controllability of an electric linear actuator. This combination delivers up to 4,800 lbs. (21 kN) of force in an electrically powered unit that functions without a complex system surrounding it. Furthermore, the unit will also deliver shock handling performance comparable to a fully hydraulic system. The boom on the signage truck might be subject to wind shear that could damage components of a traditional electric actuator. A hydraulic/electric hybrid system, however, would absorb these sudden shocks. (Figure 1)
Long-life, heavy-duty designs Machine designers building simple applications in which basic movements repeat with high frequency have also typically deployed hydraulic solutions. These provide an acceptable duty cycle of 40-80%, which contributes to a longer life, but a substantial part of that life is used up in order to maintain the actuator. A new generation of long-life, high-duty electric actuators has emerged that enables their use for simple, repetitive operations. Instead of using servo, stepper or brushed AC electric motors, long-life actuators typically use brushless DC motors. Unlike a brushed AC motor, which will overheat at high duty cycles, the brushless DC motors generate no friction, enabling duty cycles of up to
OEM Off-Highway | NOVEMBER/DECEMBER 2021
at least 35% or, depending on the load and ambient temperature, up to 100%. Other features contributing to a long-life actuator’s durability are double-circuit nuts and larger screws, which reduce another common point of actuator wear and can extend cycles from 30,000 or 40,000, improving travel time by orders of magnitude. Additional life-extending design features include strengthened screws and extra-angular contact bearings. Together, such features can extend actuator life 10 times more than a brushed motor-driven actuator that might previously have been deployed in transport-grade industrial applications And, as compared to stepper- or servo-driven solutions, brushless DC motor-driven actuators are more compact because they don’t need gearing configurations. Long-life actuators are also typically sealed for high ingress protection and lubricated for life in the factory, thereby requiring zero additional maintenance. And as an added benefit, because DC-brushed, motor-driven actuators can be run totally on 24V battery power, they are also a good choice for moFigure 2: The long-life Thomson Electrak LL actuator is designed for high duty cycle applications that do not need high precision. It includes a DC brushless motor, larger shaft and various features that extend its life up to 10 times over brushed motordriven actuators.
