Beyond Speed Control: Interesting Ways AC Drives are Used in Industry

AC Drives are everywhere you look, from HVAC units to the cranes repairing your local highway. There are thousands of different AC drives powering numerous different control systems, though instead of talking about the usual use cases for these pieces of tech, lets take a step back and go through some uncommon and interesting ways AC drives are implemented through out the industry.

Energy Recovery in Elevators, Cranes, and Ski Lifts

Picture a ski lift hauling up a group of eager snow boarders to the top of a mountain. Those motors pulling them up along the track are burning quite a bit of energy to do so. Yet when the load is off, gravity will pull those chairs back down, similar to a crane lowering a load. When using a drive that has regenerative features, such as the Allen-Bradley PowerFlex 755T, that downward work performed by gravity will turn the motor into a generator to recapture that energy and either feed it back into the facilities power system or shares it across a common DC bus to power other equipment that’s accelerating or starting up.

How Does it Work?

When a motor is being driven by its load, meaning that the load is turning the motor rather than the electricity supplied to it, the motor becomes that generator we spoke about earlier. The AC drive will detect this change and switch modes to route the incoming energy rather than fight it. A drive without this feature will burn that energy up as heat via a brake chopper and resistor. Some examples of this are:

• Ski Lifts and Gondolas: These chair lifts are usually heavy on one side and light on the other. Regen drives help stabilize the energy use for smooth transitions.
• Elevators: Energy is used to bring the elevator up, but gravity will pull it right back down when needed, transferring that energy into the power grid.
• Cranes: The same principle applies to heavy loads being picked up and lowered by industrial equipment.

Tension Control in Winding Systems

If you’ve ever tried to unroll wrapping paper or cling wrap without it crinkling or tearing, then you’ve just experienced the core challenge with tension control. Now imagine that same issue at 1,500 feet per minute with a roll of film worth thousands of dollars. Seems a bit stressful right? Thankfully AC drives step in to not only run the motor, but to actively manage how tightly or loosely material is wound.

Tension Varies with Diameter

In any type of winding application, the effective torque needed to maintain tension changes constantly. As a roll grows, more torque is needed to maintain the same surface tension, whereas a shrinking roll will need less. But too little and the material goes slack, or wrinkles. If a dancer arm or loadcell is involved, the system will need to react quickly to slight deviations and correct them smoothly.  In traditional setups a dedicated tension controller, analog sensors, and a bunch of wiring is needed to do exactly this. But with modern AC drives, this is all done internally with fewer parts and tighter response. Drives like the PowerFlex 755T utilizes Allen-Bradleys TotalFORCE technology that enables very precise position, velocity, and torque control to maintain speed regulation during winding and tension control applications.

Solar Panel Tracking

Solar Panels are the most efficient when they’re staring directly at the sun, which creates an obvious problem when wanting to maximize the output of the panels. One of the answers to this problem is by mounting the panel on an assembly that can turn and rotate at the control of a computer. While these panels don’t need to move fast, they do need to move precisely, hold their position against the wind, and start and stop without backlash or overshoot. This is where the AC drive comes into play.

How AC Drives Help Track the Sun

While the angles are determined by a tracking software, the drive is working to power the motor turning the panel, either on one axis to simple east to west rotations, or a dual axis tracker for tilt adjustment (north-south) to follow elevation angles. Rather than using a basic motor starters or hydraulic actuators, many systems adopted this method of using AC drives and motors for precise control, offering a few key benefits:

• Slow-speed precision: Drives can run induction or permanent magnet motors at very low RPM without stalling, thanks to vector control and adjustable ramp rates.
• Smooth starts and stops: Prevents jerky motion or panel oscillation that could wear out gears or joints.
• Torque limiting: Prevents overdriving during storms or snow load situations.
• Remote adjustability: Drive parameters can be tuned over time or via remote control to match seasonal solar angles.
• Low power standby: The drive can idle at ultra-low speeds for hours with almost no energy draw, making it ideal for incremental sun tracking.

Drives like the PowerFlex 525 or 753 are very good candidates for this type of application as they could be tuned precisely and eliminate the need for complex external PLC logic. The Kinetix 3 is also a fantastic option, as it’s very user-friendly, being plug-and-play compatible with various motors. AB even lists solar panel tracking as a possible application for this drive. If you would like to learn more about the Kinetix 3, we have a full breakdown here.

Retrofitting Old Machinery

Ever wanted the reliability and robustness of an old drill press but with the brains and accuracy of a CNC machine? It is absolutely possible, and with the right amount of calibration, can be quite the formidable piece of equipment. Old machines like drill presses and lathes are built like tanks but are mechanically controlled. You have to shift a pulley or belt to change the speed, or the on/off is a simple contactor. There is no flexibility, no automation, and certainly no G-code in sight… until now.

Breathing New Life into an Old Machine

When retrofitting these machines into CNC tools, two main challenges arise:

1. Motor speed and torque must be digitally controlled
2. Motors need to respond precisely to motion commands from a controller

This, of course, is where AC drives shine. Rather than relying on stepped pullies or gearboxes, a VFD will allow you to adjust the motor speed on the fly, using a digital signal from the CNC controller. The bed of a drill press can also be retrofitted to be controlled so that the press can make multiple, precise holes in one command. Add a oil pump to drip on the bit and it’s a good example of a semi-automated system, especially if its utilized for one specific task. Home the tool head, load the part, and let it do its thing before replacing it with another blank part and doing it again.

Final Thoughts

AC drives are all around and are quite a versatile piece of technology found in settings that might just surprise you. They come in all shapes and sizes, from large name brands like Allen-Bradley to smaller more specialized units. If you are looking to embark on a project like this and need a bit of help, why not give us a call? We have an extensive list of drives and experts who can help point you to the right direction or pick out drives and motors that could work with what you want to do.