Diesel-powered, towable generators work in an impressive diversity of sectors. These portable gen sets can end up providing energy for chicken coop heaters on a poultry farm, carnival rides at your local county fair or backup power during severe weather events. We’re talking about tow-behind generators in the 8- to 500-kW or 8- to 650-kVA range, produced by brands like Generac, Doosan Portable Power, JCB and Atlas Copco.
“Versatility is a key design requirement as usage can vary significantly,” confirms Aaron LaCroix, product manager with Generac Mobile Generators. “When choosing a tow-behind diesel generator, customers should be looking for options that allow for use in different applications. Design elements we implement on our units include voltage selector switches for simple operation, remote start and stop capability, extended run time and other customizable options. They also should take into consideration units that offer load management technology and cold weather options. All of these features make owning and operating a mobile generator easier.”
While a towable generator can work in a variety of applications, it is also not a one-size-fits-all machine. There are a variety of tow-behind generator models, sizes and technologies on the market for a reason. The goal is to have a generator that provides enough power that it doesn’t become overloaded but also not underpowered (too light a load can cause issues like wet stacking). So, let’s delve into a few keys for picking a unit and the latest technologies trending in the industry.
Choices in Portable Power
The towable generator market has a wide range of power nodes, technology features, model configurations and brands. That impressive range means power and load demands can fluctuate greatly depending on applications of even one customer. There are several factors to consider to help narrow down a search for a unit that fits a crew’s power needs:
- Are you looking for prime, continuous or standby power generation?
- What voltage and frequency are needed for the project?
- What will the generator(s) be powering?
- What amount of power (current/amperage) is needed?
- How far will the generator be from where it is tied in?
- How will the power be tied in?
- How many hours per day will the generator be running?
- Are you looking for single-phase, three-phase power or both?
- Are you interested in alt population engines like propane or natural gas?
- Do you want to rent or buy?
What Type of Power Generation?
Generators can work in prime, continuous and standby power applications — and each category has a rating. Prime running power means all-day-long apps at near maximum load (like 80 percent capacity), while standby or emergency power generators won’t run more than a couple of hundred hours a year. Mobile units can operate for standby, prime or continuous duty and have ratings for that, but towable units are usually considered prime power machines.
The primary concern when deciding what type of generator is best for an application should be making certain you get the right electrical configuration — phase, voltage, kW, kVA and hertz. Knowing how the generator will be used makes it possible to calculate the necessary voltage and amperage (amps) — information typically displayed on the equipment data plate. Knowing the voltage and amps allows you to determine kilowatts or kilovolt-amperes, which dictates the amount of electrical power needed to operate the load. Ideally, a generator should run at 75 percent of load, which is why a 100-kW generator should not be operating only a 20-kW circular saw.
“We have a lot of people using generators in applications that are way oversized for the application, so they are under utilized,” explains Travis George, Doosan Portable Power product manager. “That led to a lot of heartburn in our industry. Luckily, we are kind of getting on the back end of that, hopefully, with some of this newer technology coming out. But I still think knowing the application, knowing the sizing, the requirements on the jobsite. There are specific installation requirements, you know, per code. I think those things will go a long way, and it’s not always very intuitive. It’s hard. It’s hard to size a generator, but it’s worth it to take the extra step. A right sized generator is a happy generator.”
Calculating voltage will require understanding power ratings like running watts (often called continuous power) and starting watts (often called maximum power). Running watts are what the generator can produce continuously while running, and starting watts are what it can produce for a short time to help start motorized electrical tools. Typically, the biggest issue when sizing a generator is that motor starting power, noting only equipment with electrical motors require additional power to start.
Generac’s Most Popular Model
“Our most popular tow-behind generator is our MDG25,” says Aaron LaCroix, product manager with Generac Mobile Generators. “It is popular because it is versatile and designed to be used in multiple applications. It is the right size for powering outdoor events, construction jobsites and other infrastructure projects. Our machine utilizes a proven Isuzu engine and can be customized for different operating environments. It is also one of the highest volume three-phase mobile generators on the market. Customers that are attracted to the MDG25 come from a diverse range of businesses. The MDG25 stands out with its 500-hour standard service interval and 24-hour fuel tank. The unit also features multiple alternator options including increased motor starting capability and selectable 600V output for Canadian markets. Customers can also customize the units further with cold weather kits for extreme weather and cam locks for power distribution.”
“It is very important to correctly estimate your power needs to ensure proper operation,” says LaCroix. “To correctly estimate your power needs you need to evaluate the applied loads and what motor starting power may be required. This is done by evaluating the load profile or duty cycle of the machines that are going to be operated. The Generac mobile products website provides tools for calculating loads and sizing generators.”
Totaling up your power needs requires a little math, so finding a website to help is always a double plus. You’ll need to know the items you want to power, the item that needs the most starting watts and the running watts of lesser powered items. Add all of that up to match a generator’s power range in prime or standby modes. Tow-behind generators are built to produce three-phase or single-phase electricity or both. Three-phase power (the norm for bigger towable generators) produces three separate waves of AC power operating in a sequence, ensuring continuous flow, ideal for commercial applications, while single-phase voltage alternates continuously and is geared for light loads that usually don’t go above 40 kW. A three-phase power generator can offer both types and might be broken up into ranges like: 120/240V single phase; 208V three phase; 480V three phase; and 600V three phase (the latter for Canada). For example, most homes in North America are wired for 120/240V single-phase power and most commercial and industrial buildings in North America use 277/480V three-phase power. So, check out how easy it is to operate the voltage selector.
“I believe it is very important to familiarize yourself with the machine you are about to operate,” advises Lee Jaquiss, general manager of Power Products North America at JCB. “Through locating safety features as well as identifying where key electrical and mechanical connections are located, you can in turn operate the machine safely and correctly, avoiding any unnecessary downtime.”
Towable, diesel-powered generators can be customized to meet a variety of job parameters with choices of cold weather packages (from block heaters to fuel filter heaters), engines (diesel to gaseous), trailer options (electric brakes to various hitches) and tech add-ons (alternators, varying control panels and extended run fuel systems for both fuel and DEF). In addition to the right size towable diesel generator, there are also accessories to help effectively power the jobsite like distribution panels, circuit breaker panels and transformers. Now, let’s recap some of the biggest trending technology in the towable power generation market in 2021.
From ensuring load match to paralleling units, diesel generators engineered into a trailing format have become sophisticated machines with the ability to provide precise power pretty much anywhere at any time. While generators can do a variety of jobs, power generation has become more specialized and technologies like telematics (for instance) are taking product ownership, usage, maintenance and security to new digitized levels. Telematics is an umbrella term for a variety of technologies and services that monitor a unit, collecting and sharing digital data on everything from systems analysis (maintenance) to location (theft prevention). A telematics monitoring device would be installed on the unit or multiple units, and vested parties would be able to monitor those machines via smart devices like a computer, phone or tablet. The service comes with a monthly fee but is usually free for the first two or three years after purchase (or maybe it’s a part of a rental agreement).
“Telematics is something that we are very vocal about,” says Jaquiss “Our customers get it and are utilizing vitally important real-time data 24/7. Another key market trend is the shift towards synchronizing, from 100 kW and above. Using our intuitive plug-and-play system, you can operate multiple generators together, which allows you to more effectively and efficiently manage your equipment.”
The paralleling process involves the physical connection of two or more generators and the synchronization of their outputs to create big power. Generators can usually be paralleled together as long as their frequencies and voltages are the same, but there are of course limitations with age, size and brands. Some factors to consider when paralleling include synchronization of units, voltage regulations, overall load balance, altitude of the site and ambient temperature, what it takes to start the motors and surge capacities. The paralleling process allows contractors to have flexibility with their power, conserve fuel consumption and save runtime on the machines, which means a higher resale value. Atlas Copco notes it can link up to 32 QAS 700 models together to provide up to 22.4 MVA of stable power.
On the engine side, Tier 4 Final emissions regs have produced cleaner, quieter and more efficient diesels with near-zero emissions, but these high-tech diesel engines are now engineered with additional aftertreatment technologies. Each manufacturer applies these and other aftertreatment technologies to various power bandwidths, depending on the emissions regulations of each country, and these technologies can have a big effect on generators compared to other off-highway equipment.
“Diesel engines nowadays, they have a lot of aftertreatment to support the engine to meet the emissions requirements,” explains George, “and what happens is the engine is not being fully utilized. So, if it’s running at low load or has low demand, there’s just not enough heat in the combustion chamber, in the engine system, to properly burn off all of this carbon buildup, and it ends up blocking the aftertreatment, plugging it up. The machine will shut down, and they’ll have to call a service tech out to make a repair. It’s a very costly and time-consuming incident. Our solution is basically an onboard solution. There’s no customer interface. [The unit] artificially adds a load to the engine to increase the amount of heat that is provided into the combustion chamber and therefore downstream to the exhaust system.”
Diesel generators with Tier 4 Final engine systems operating below 30 percent of rated capacity or in extremely cold environments often cannot produce the required internal heat to effectively complete diesel particulate filter (DPF) regeneration — an aftertreatment process that consumes particles and impurities in the exhaust stream to meet those emissions standards. Similarly, Tier 4 Final engine systems equipped with selective catalytic reduction (SCR) aftertreatment technology require elevated exhaust temperatures for periodic conditioning of the SCR system to maintain efficiency and performance. To combat this, the Doosan Portable Power-patented Intelligent Load Management System (ILMS) creates supplemental heat within the exhaust system, which aids in the passive regeneration process required for reliable generator performance without limiting the generator capacity by adding a sizable load. The system requires no operator control or monitoring. Another alternative to this is applying that telematics tech we just discussed.
“To mitigate low-load related downtime,” says Jaquiss, “if your generator has been operating for more than 500 hours below 30 percent of the machine’s prime rated kW, the controller is programmed to alert the user at the machine via an alarm on the control screen and via telematics on the LiveLink homepage, that the recommended course of action is to increase load to 100 percent of the prime rated kW load of the generator for two hours. This can be done by increasing the application load in which the generator is supplying or by connecting the machine to an artificial load bank. By notifying the user ahead of time, the correct course of action can be planned and downtime can be reduced.”
\There are different types of power or load management systems too. Atlas Copco and its sister brand Chicago Pneumatic, for example, offer a Power Management System (PMS) — specifically for paralleling applications — aimed at optimizing fuel consumption and expanding the generator’s life. Generac Mobile generators with Final Tier 4 John Deere engines feature an innovative exhaust temperature management (ETM) system that provides supplemental heat when necessary to avoid wet stacking issues, eliminating the need for a supplemental load or heat device.
Doosan Portable Power’s G570
The new 570-kVA Doosan Portable Power G570WCU-2B-T4F mobile generator has an advanced Cummins X15 Performance Series diesel engine with an integrated thermal management system that enables operation in harsh environmental conditions. The G570 comes standard with a DEIF AGC4 generator paralleling controller and an advanced digital voltage regulator. Together, these technologies make it the most capable generator on the marketplace while also simplifying setup for parallel operation. You can parallel the G570 with up to 32 generators at a single time on a common bus. Models within the Doosan family, such as the G400WCU-T4F and G325WCU-T4F, are compatible, and so are non-Doosan generators you may already have in your fleet. For more info, visit doosanportablepower.com.
For companies using generators in remote locations, whether they are running sprinklers on a farm or empowering operations in remote oil and gas projects, perhaps no development is more exciting than the growth of remote controls. Remote control operation can allow contractors to start, stop and control a unit without being onsite. There are bi- or tri-fuel add-on systems for generators, enabling diesel units to use natural gas or some other variant, saving fuel costs compared to burning diesel fuel alone. By incorporating battery packs or supercapacitors in the gen set package, excess power can be captured and stored. This allows the generator engine to be turned off while stored power in the batteries or capacitor is utilized, saving on fuel consumption.
Overall, the towable generator market continues to evolve — from ultra-silent generators, used in events and movie filming, to energy storage technologies linked to the evolution of battery technology. It allows these mobile gen sets to power everything from giant tower cranes in the middle of a city to gold mining wash plants in remote regions of Alaska. It’s an impressive combination of possibilities engineered into a mobile and easy-to-operate package.
“A lot of effort goes into designing a tow-behind diesel generator to meet the customer’s expectations,” says LaCroix. “We strive to design, engineer and manufacture a rugged, durable machine that gets the job done for our customers, and we make sure that machine is easy to use and maintain while running smoothly on almost any jobsite.”
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