July/August 2008
Solid-state magnet controllers have no moving parts, making them smaller, lighter, and less likely to break than their mechanical counterparts, whether on their own or as part of a generator-controller set. That benefit often comes at a higher cost, however.
By Jim Fowler
Years ago, people called mechanical magnet controllers "clapper boxes" because of the noise they make when the contactors come together to energize and discharge energy from the magnet. Those controllers continue to be popular in the scrap industry due to their longevity, simplicity, reliability, and cost. (For details, see the "Equipment Focus" article in the May/June 2008 Scrap.) That said, solid-state magnet controllers quietly have been catching hold.
In the simplest terms, solid-state controllers use digital circuitry rather than mechanical contactors and resistors to control the flow of electricity to and from the generator and lifting magnet. A combined generator and solid-state controller can be smaller and lighter than the equivalent mechanical variety, and some manufacturers say these controllers run cooler than mechanical controllers, which helps prolong magnet life. Further, because it controls the current, "solid-state technology requires less power consumption than mechanical units and therefore reduces associated energy costs," says Rich Edling, a senior electrical engineer for Winkle Industries.
The primary benefit of solid-state controllers, however, is that they have no moving parts, which means no parts to break, no parts to repair, and no parts to wear out and replace, resulting in less down time, lower maintenance costs, and longer life. "There is no maintenance with the solid-state controller," says Ken Richendollar, sales manager of Ohio Magnetics (Maple Heights, Ohio). "When they fail, they fail completely, but they don't fail very often."
That benefit comes at a cost, however. Solid-state generator and controller sets typically are more expensive than mechanical magnet controllers and separate generators. "There is a big difference in cost, and that's why the mechanical controllers are so popular," Richendollar says.
European companies have manufactured solid-state generator-controller combinations for years, some of which they sell in North America. U.S. makers of magnets and controllers have come to the solid-state scene more recently, selling both generator-controller packages and standalone controllers. Here's a look at the companies offering these products in North America.
Controller-Generator Packages
All of the European manufacturers of solid-state magnet controllers sell them as integrated generator-controller packages, as does one U.S. company. As with the mechanical variety of magnet controller, solid-state controllers can run off of generators powered by a belt connected to the base machine's engine, a separate diesel or gas engine, or the base machine's hydraulic system, though not every manufacturer offers every option. Hydraulically driven generators are popular, but manufacturers emphasize the importance of the generator receiving a steady, consistent flow of hydraulic power to prevent destruction from "over speed," excessive wear, and poor operation of the generator and magnet. "There is a science to it, and you must do it right," says John Fryklund, president of Job Machinery (Apple Valley, Minn.). "If not installed properly, it can lead to serious trouble. The generator must have a priority hydraulic supply—fluctuations in hydraulic flow are unacceptable."
For five years, Bateman Manufacturing (Orillia, Ontario) has been selling the magnet generator system from GTS (Mogglingen, Germany) as part of a self-contained unit powered with either a diesel engine or hydraulics, says General Manager Mark Vandenberg. "Companies that have standard excavators and want to use a magnet on the machine have the choice of using either the diesel or the hydraulic-driven package."
With GTS' solid-state controller and a brushless AC alternator as the generator, the unit is completely electronic and contains no wear parts, Vandenberg says. The controller converts the power from alternating to direct current, he adds.
The GTS system puts 280 volts into the magnet in the first few seconds to charge the magnet faster, Vandenberg says, resulting in a quicker pull. Along the same lines, he says, "when you push the control to release the scrap, [the controller] reverses polarity, throws the scrap off, and absorbs the energy from the magnet very quickly." Further, he says, "it has a ‘sort' option, which is a slower pull and slower release so you can drop heavier items off the magnet but still hold smaller items for sorting."
If a company plans to dedicate a specific material handler to the magnet, Vandenberg advises using the hydraulic drive with a supplemental hydraulic pump. The hydraulic drive "is designed to run all the time, so it provides more consistent power to accommodate a heavier duty cycle," he says. The benefit of using a small additional pump rather than drawing fluid from the main hydraulic pump is consistency, he adds. "The generator doesn't require a lot of flow; it just requires a consistent flow of oil."
If an additional pump is not possible, though, "we have a diverter valve system for use with the main pump," he says. "The excavator and its hydraulic system [determine] the approach you can take, but an additional pump—a dedicated pump to run the generator—is the best installation you can do."
Gensco Equipment (1990) (Toronto, Ontario) has been selling hydraulic magnet generators by Dynaset (Ylöjärvi, Finland) for 10 years. The Dynaset package consists of a hydraulic motor, generator, magnet controller, hydraulic speed regulator, priority valve, and electronic control kit—everything needed to power the magnet, says Gensco President Alan Zelunka.
The hydraulic speed regulator "has been set at the factory to fit the customer's machine," Zelunka says. It controls the flow of hydraulic oil based on the hydraulic pressure "to keep the generator speed consistent" at 230-volt DC power "when the incoming oil flow and pressures vary. Continuous flow is critical," he emphasizes.
The Dynaset generator and magnet controller combination takes up little room and has a great power-to-size ratio, he adds. The operator controls the generator from the cab with a power-on switch and a single push button. "Magnet power is immediate," he says, "and it usually takes 1.5 to 3 seconds for demagnetization, depending on the inductance of the magnet and the loaded material."
Job Machinery is the North American distributor of Mozelt synchronous power systems manufactured in Duisburg, Germany. This integrated design—which eliminates the controller, rheostat, and fuse box, replacing them with solid-state technology—transforms brushless three-phase voltage into DC voltage in the generator. One on-off control button in the operator's cab controls the contactless delivery. The computer chip senses what's going on throughout the system, Fryklund explains. A menu of LED signals in the cab reports normal activity, such as operating hours, and troubleshoots problems. "It reports fault signals, such as a short, which automatically protects itself; a line open; or if your operating rpm is incorrect," he says, and "it tells the operator if the magnet is overheating, which means a loss of pick power.
"This ‘brain card' manages the generator system to optimize its performance," regulating the voltage automatically for the magnet size and material being handled, Fryklund says. Further, the system is independent of the on-board electrical system and provides its own voltage for control and monitoring, he says.
Job Machinery offers the integral generator set in diesel, hydraulic, and belt-driven models from 10 kW to 30 kW, giving buyers options to fit new or older machines. "Many used material handlers don't have the right hydraulic oil supply to do a hydraulic drive generator, so the compact diesel gen-set drive offers an easy-to-mount alternative that can migrate from machine to machine," Fryklund says.
Caterpillar (Peoria, Ill.) will introduce its newest hydraulically driven, solid-state controller system in August. The company offers generators ranging from 15 kW to 40 kW, all mated to the same controller. The direct-current generators work continuously (a 100-percent duty cycle), notes Sales Engineer Dennis Sorbel. An automatic boost cycle quickly brings the magnet up to maximum lift capability, decreasing cycle times.
Several features of the generator protect it from fluctuations in hydraulic power. The manifold has a priority flow-control system that maintains the generator's revolutions per minute regardless of the engine speed. "If your engine rpm falls off when you are doing other things with the machine, the generator stays up to speed, which improves generator and magnet life," Sorbel says. A soft-start solenoid moves some of the oil from one side of the manifold to the other for a few seconds, until the generator comes up to speed. This prevents a hydraulic surge that could damage the coupling between the motor and the generator. A reverse-flow check valve allows oil to circulate in the motor until the generator winds down to a stop, also protecting the hydraulics. Another solenoid allows the generator to bypass the flow from the dedicated pump, ensuring it only operates when it's in use.
The new system will be compatible with Cat's Electronic Technician service, Sorbel says, in which an operator who plugs a laptop computer into the controller can get immediate feedback on 10 to 20 operating parameters.
| Solid-State Magnet Controller Manufacturers The following companies make generator-controller packages or standalone solid-state controllers. Listed are models used in the scrap industry and their prices (when provided). Bateman Manufacturing
705/733-2668
www.batemanmanufacturing.com
Diesel generator-controller systems in six generator output sizes, from 6 kW to 30 kW, $10,000 to $30,000
Hydraulically-driven systems in four sizes, from 13 kW to 30 kW, $16,000 to $30,000 Caterpillar
309/675-4839
www.cat.com
Generator-controller systems in sizes ranging from 15 kW to 40 kW, $40,000 Control Services
773/290-1629
www.emagcontrol.com
E-mag controller, $4,680 The Electric Controller and Manufacturing Co.
800/240-1230
www.ecandm.net
Controller only, 10 to 120 amps, $5,500 Gensco Equipment
416/465-7521
www.genscoequip.com
Seven Dynaset generator-controller models, from 6 kW to 40 kW, $10,000 to $30,000 Hubbell Industrial Controls
336/434-2800
www.hubbell-icd.com
Product in development Job Machinery
612/961-8893
www.jobmachineryinc.com
Generator-controller models from 10 kW to 30 kW Northwest Magnet
503/282-1441
www.northwestmagnet.com
North Star controller, $6,895 Ohio Magnetics
216/662-8484
www.ohiomagnetics.com
Optimizer controller, 0 to 150 amps, $13,000; 0 to 350 amps, $22,500 Walker Magnetics
508/853-3232
www.walkermagnet.com Winkle Industries
330/823-9730
www.winkleindustries.com
OptiCon controller, 0 to 350 amps, $10,000 Publisher's note: NASCO-OP also is a source for magnet controllers and generators used in the scrap industry. Contact Bob Bedard at 800/321-3396 or visit www.nascoop.com. |
Controllers Only
Several U.S. companies manufacture solid-state magnet controllers without generators.
Ohio Magnetics recently introduced the Optimizer, a solid-state integrated bipolar transistor (IGBT) magnet controller that comes in two sizes—0 to 150 amps and 0 to 350 amps. Richendollar touts the product's advantages over mechanical controllers. "They use less power, run cooler, and eliminate voltage spikes, which protects the entire system," he says. Further, "with multiple operating modes, the lift, hold, dribble, drop, and clean cycles are improved to maximize performance and prolong magnet life."
Winkle Industries (Alliance, Ohio) offers its own solid-state IGBT magnet controller, the OptiCon, which increases magnet lifting capacity 15 percent to 40 percent, Edling says. In addition, he says, "the new technology eliminates damaging magnet discharge voltage spikes, and [it] reduces current after it completes the lift cycle." This means "the magnet runs cooler, which means the magnet lasts longer and has quicker duty cycles, allowing for decreased maintenance costs and increased throughput." OptiCon comes in current ranges from 0 to 350 amps and voltage ranges from 120 to 300 VDC.
Control Services' (Westmont, Ill.) e-mag magnet controller, launched in February 2007, uses a slightly different setup. Its input control system runs the magnet load cycle using any direct-current generator as long as it has a 24-volt field configuration, explains Control Services President John Samila. "E-mag is ‘one size fits all,'" he says—it works with any magnet and generator combination. "It will run the generator at the correct voltage output no matter what the speed of the generator is, from 1,500 to 3,600 rpm."
The benefit of this "speed independence," Samila says, is that it requires only simple feed/return hydraulic connections, no flow-control valves, when connected to a hydraulically powered generator. It also works with a mechanically driven generator. It's designed so that "engine and hydraulic-system performance have no bearing on magnet and controller performance," he says.
Like other magnet controllers, this 12-by-10-by-16-inch unit "runs cool, no maintenance is required, and there are no wear parts," Samila says. "There is breaker safety in the unit," he adds, "and I put a 10x multiplier on each of the parts in the controller to make sure they are 10 times more powerful than needed, currentwise."
Some manufacturers' solid-state magnet controllers are not yet on the scrap recycling market. The Electric Controller and Manufacturing Co. (St. Matthews, S.C.) is field-testing Mag Pulse, an all-electronic magnet controller, for release this fall. "We have it on a material handler in a scrapyard now," says Engineering Manager Randy Creech. "The picking is going to be the same because [it's receiving] same voltage from the generator," [as it would with a mechanical controller?], but "we're seeing quicker, cleaner drops." Mag Pulse doesn't require a discharge resistor, he says, and "because it's all solid-state, there is no preventive maintenance."
The system is designed to ease maintenance, Creech says. "To make it simple, we put [light-emitting diodes] on the control board that give the operator the status of what's going on with the system. If there's a problem, we ask what LEDs are being displayed, and we can give a diagnosis."
The Mag Pulse controller, with a range of 10 to 120 amps, weighs an estimated 40 pounds, compared with 125 to 130 pounds for the company's mechanical controller.
Walker Magnetics (Worcester, Mass.) has sold its new solid-state controllers to U.S. steel mills, but Sales and Marketing Manager Jim Butke says Walker has not yet marketed them to scrapyards. He anticipates the company will offer three models with prices comparable to the company's mechanical controllers.
Though Hubbell Industrial Controls (Archdale, N.C.) also has a solid-state controller in development, Senior Applications Engineer Roger Moseley says they're not necessarily the best answer for the scrap industry. Though the move from electro-mechanical to solid-state controllers is bound to happen eventually, he says, "I don't see [the solid-state controller] becoming a mainstay in the immediate future due to the maintainability issue. Most solid-state controllers must be returned to the manufacturer or an authorized service center for repair. This can result in longer down times than would occur with an electro-mechanical controller, which would be normally serviced in-house."
Alternative Technology
One product in this market can't truly be called a magnet controller because it doesn't come between the generator and the magnet. The North Star solid-state controller from Northwest Magnet (Portland, Ore.) controls the generator itself. This product, available since 1997, never interrupts the circuit between the generator and the magnet—they're always connected, so there's no high-voltage discharge. Instead, explains Northwest Magnet President Marius Andreica, "we energize the fields on the generator—we tell it when to turn on, to what voltage, for how long, and when to reverse [polarity]."
The controller begins a cycle with a higher voltage, Andreica explains. "When you turn it on, rather than [reaching] 230 volts, the North Star goes up to 290 or 300 volts." That creates "an ‘extra lift' period that allows you to pick up 50 percent more steel with the same magnet," he says. "Once the crane lifts out of that pile, there is no need to energize the magnet at such a high rate, so the voltage drops to 190," keeping the magnet cooler.
To conclude the cycle and drop the metal, "we reverse the field and, rather than create a surge, it turns the generator into an electric motor that draws the power from the magnet," Andreica says. "It takes all of the energy and just spins the motor. We continue in the same direction, which reverses the charge to the magnet and causes it to throw the metal down. If the magnet was 200 volts when we reversed the field, it gradually goes to 0 and continues to -200 and then back to 0."
The controller operates at about 2 ½ amps, Andreica says, and "the whole thing is protected by a 5-amp fuse. It will run anything from the smallest [magnet] to a 78-inch magnet. If you want to switch between magnet sizes, you don't have to change the controller." It also works with nearly all generators, he says.
The North Star generates no heat and requires very little maintenance, Andreica adds. "Two timers need to be replaced after 1 million cycles, and the relays [which] handle 5 amps have to be replaced after 1 million on-and-offs."
Clearly, scrap processors have a wide range of magnet controller options—from traditional mechanical devices to the newer solid-state units. Buyers will no doubt consider their cost differences, which must be weighed against maintenance requirements, production benefits, power use, and the life expectancy of the magnet, controller, and generator. Calculating the return on investment of a controller may take a bit of doing, but it also may well be worth the effort. As with any purchase, manufacturer reputation, service and parts availability, and customer satisfaction should be a part of the buying equation. •
Jim Fowler is retired publisher and editorial director of Scrap.
Solid-state magnet controllers have no moving parts, making them smaller, lighter, and less likely to break than their mechanical counterparts, whether on their own or as part of a generator-controller set. That benefit often comes at a higher cost, however.