Introduction: Size a portable industrial generator by matching starting surge, phase, voltage and start method to the tools a crew actually runs.
A crew arrives at a site with no grid connection, unloads a compact open-frame set, and expects it to run a breaker, two angle grinders and a string of work lights without tripping. That scene is where the real buying decision sits. Before an RFQ goes out, the procurement lead has to turn that scene into numbers: continuous running load, the surge each motor pulls at startup, single-phase or three-phase output, the site voltage, and whether the operator walks over to pull a key or lets the set start on its own. Guessing in kilowatts alone is how crews end up with a set that stalls on the first hammer drill or one that is far heavier and thirstier than the job needs.
The first figure to collect is continuous load, and it comes from nameplates, not from memory. Walk the site and write down every tool and light the crew uses at the same time: drill wattage, grinder wattage, compressor rating, lighting count, plus any small charger or monitoring box. Rotating generation is a straightforward conversion of mechanical drive into electrical output, so the set only has what the engine and alternator can deliver at once. Add the nameplate values of everything running together, then compare that total against the 1.5-20kW band rather than against a single tool rating. A crew running lights, a drill and a grinder at the same time is a very different requirement from a crew running the same tools in sequence, and the second group often fits a smaller set in the same range. Starting surge is the second figure, and it is the one that decides most site arguments. Motors in drills, grinders, saws and compressors pull a heavy current spike for a fraction of a second before settling to running current, and the set has to carry that spike without stalling or dropping voltage far enough to reset equipment. Note which tools start under load and how many can start at once. Sizing on continuous load alone, then adding a small margin, is the common failure: the set runs quietly all morning and shuts down the moment two grinders are triggered together. Giving the full motor load its due before selecting an output within the range keeps surge capacity where the work happens. There is a practical upper end to that reasoning as well. An open-frame, air-cooled set in this range is a portable site tool, built to be moved between work areas and started for shifts of intermittent work. It suits crews that run tools, lighting and small equipment through a working day. It is not a 24/7 heavy main power plant for a large site, and treating it as one pushes the wrong product into the wrong duty. If the load list has grown into continuous multi-shift demand, the honest answer is a different class of machine, not a bigger number in the same portable range.
Once the load figure is settled, phase becomes the next fork in the road, and it is decided by what is plugged in, not by preference. Handheld tools, lighting strings, chargers and small appliances are typically single-phase. Larger motor-driven site equipment, pumps and heavier fixed machinery are typically three-phase, because three-phase power delivers the same work at lower current. Take the list of tools and mark each one as single-phase or three-phase; if every item is single-phase, a three-phase set adds cost without adding useful capability. If a genuine three-phase load is on site, a single-phase set cannot substitute for it, no matter how the wattage compares.
Single-phase output covers the daily routine of most light construction and fit-out work: drills, grinders, cutters, task lighting, small pumps, chargers and monitoring devices. It is simple to distribute through extension boards and site leads, and it matches the 110V, 220V and 230V single-phase configurations offered across the portable range. The judgement call here is distribution, not just capacity. A single-phase set running long leads to distant work areas loses voltage over distance, so keep runs reasonable or move the set closer to the work. For a crew that works in one zone at a time, a single-phase open-frame set is usually the cleanest, lightest answer for the same output band.
Three-phase output is the right specification when the site runs motor-driven equipment designed for it: larger pumps, hoists, fixed bench machinery, or three-phase site distribution boards. The key word is balance. A three-phase set performs best when the load is spread reasonably evenly across phases; stacking most of the draw onto one phase wastes capability and can cause uneven voltage. List the three-phase loads first, note their starting current, then add single-phase tools on top. A three-phase set in the 1.5-20kW band can still run single-phase equipment, so it remains a valid choice when a site has a mix, provided the total and the balance are worked out before the RFQ.
Voltage selection is a short conversation with a big consequence. The portable range covers 110V, 220V and 230V at 50Hz or 60Hz, and the correct pick depends on the tools the crew already owns and the local supply they interact with. A crew carrying 110V site tools on a 60Hz market has one answer; a crew running 230V single-phase equipment on a 50Hz supply has another. Write the voltage and frequency into the RFQ exactly as the tool nameplates show them, and state whether the set is single-phase or three-phase. Getting this right the first time avoids site adaptors, mismatched plugs and the voltage-regulation problems that follow when a set is asked to serve equipment it was not configured for. Starting method comes next, because it shapes the daily routine. Electric start turns the engine over from a key or button, which saves the operator from repeated pull-starting on a cold morning and keeps the crew moving. Auto start goes further: the set starts itself when it receives the signal, which matters when the power source sits away from the work position, when the site is unmanned overnight, or when a small backup duty needs to restore power without someone walking over to the frame. A 9L tank covers a working shift and a 15L tank stretches the same routine further, so pair the starting choice with how long the crew actually runs between refuels and how far the set sits from the point of use. Both choices should be written as requirements, not preferences. State the voltage, frequency, phase, required output, starting method and expected daily running hours, and let the factory map that to a specific configuration. Diesel and gasoline are separate power options in this range, so name the fuel you want rather than assuming a single unit covers both. Exact power-to-engine mapping, dimensions, weight, fuel consumption, noise level, certification, lead time and price are confirmed against your requirement at quotation stage, which is exactly what an RFQ is for.
Choosing a portable industrial diesel generator for site power comes down to four written numbers: continuous load, starting surge, phase and voltage, plus the starting method the crew will live with every day. Get those onto one page and the 1.5-20kW open-frame range becomes easy to navigate — an air-cooled, 3600 RPM set with a copper wire core, voltage regulation, and a 9L or 15L tank for shift-length running. Tianfa Generator builds this range for crews that move between work areas, with electric or auto start and single- or three-phase output to match the tool list. Send the load list, site voltage and phase, and start preference, and the team will come back with a configuration and price.
A: Add the nameplate wattage of every tool and light that runs at the same time to get continuous load, then check the starting current of the motor-driven tools, since drills and grinders pull a heavy spike for a moment at startup. Size for continuous load plus that surge rather than for running load alone, and compare the result against the 1.5-20kW range. Send the tool list with running hours to the factory so the exact configuration can be mapped to your duty.
A: Let the tools decide. Handheld tools, lighting and small appliances are single-phase, so a single-phase set keeps things simple and light. Three-phase output is the right call when the site runs three-phase pumps, hoists or fixed machinery, and it also serves single-phase tools as long as the load stays reasonably balanced across phases. Mark each tool as single-phase or three-phase before requesting a quote.
A: Electric start turns the engine from a key or button, replacing pull-starting and speeding up the morning routine. Auto start adds a self-starting function that brings the set online when it receives the start signal, which suits unmanned sites, remote-mounted sets or backup duty where nobody is standing next to the frame. Both are available in this range; state which one fits your operating routine when you send the RFQ.
How electricity is generated - U.S. Energy Information Administration (EIA)
