Introduction: A gear motor nameplate lists several numbers that only make sense when read together, because each value limits the others.
A nameplate is often treated as a label to copy onto a spare-part request, yet on a right-angle gear motor it works more like a small map of limits. Maintenance teams run into trouble when they read one field in isolation: a large torque figure looks reassuring until the unit is asked to run at a speed it was never rated for, or a replacement is ordered on frame size alone while the duty note is ignored. Power, output speed, torque, ratio, duty, and mounting notes on a nameplate connect to each other, and a wide helical-bevel gear motor family shows why that matters in practice.
A gear motor nameplate looks like a list of separate specifications, but every line on it describes a limit that holds the others in place. The power rating describes what the motor can deliver at its design point. The output speed describes how fast the shaft turns. The permitted torque describes how much turning effort the gear unit can pass through without being overloaded. The ratio explains how the input shaft speed was converted into that output speed. The duty note says whether those values are meant for continuous running or short bursts. Read one field alone and the picture is incomplete; read them together and the machine's real operating window appears. Take the spread across a single wide family, such as the KC series from SLTM, which runs from KC37 to KC187. Across those frame sizes the published envelope covers 0.12 kW to 200 kW, output speeds of 0.15 to 270 rpm, permitted torque from 180 N·m up to 50,000 N·m, and ratios of 8 to 198. Those are outer edges, and the 50,000 N·m figure belongs to heavy-duty sizes such as KC187 rather than to every model in the line. Two units with the same series name can differ by more than a hundred times in torque, which is exactly why the plate on the unit, not the catalog family, is what gets compared against the machine in front of you.
The four main fields are not independent. Power, speed, torque, and ratio sit in one equation, and moving any one of them changes what the others mean at the shaft. The relationship is the same one used in general shaft-mechanics references and in motor rating standards: power is torque multiplied by rotational speed, with unit conversions applied. For geared motors the practical form is T = 9550 × P / n, where torque T is in N·m, power P is in kW, and output speed n is in rpm. That single line explains most of the confusion people have when comparing two units.
Because torque rises as speed falls at a fixed power level, an output speed figure is part of the torque statement, not a separate item. A unit rated at 1,500 N·m at 20 rpm and one rated at 1,500 N·m at 60 rpm are working under very different internal loads even though the torque number is identical. The output shaft has to carry that turning effort, so shaft torsion is a real design limit in every unit. In practice, when a maintenance team finds a drive running slower than expected, the torque duty on the gears and output shaft has not stayed constant — it has moved. Checking actual shaft speed with a tachometer against the nameplate value tells you more about whether the drive sits inside its rated window than reading the torque figure alone.
A gearbox does not manufacture power. It trades speed for torque, and a small share of the input is lost to friction and churning in the gears and bearings. If the ratio goes up, the output shaft turns more slowly and each turn carries more torque, while the motor's power rating stays roughly where it was. That is why a higher ratio does not convert a light-duty unit into a heavy-duty one: the housing, bearings, and output shaft still have their own torque limit, printed on the nameplate as permitted torque. A ratio change also shifts the drive away from its intended efficiency and cooling point, so ratio, torque, and duty are always weighed together.
The model code is a size reference, not a quality grade. On a family such as KC37 to KC187, the number is tied to the frame size, and larger frames generally bring larger bearings, larger output shafts, and higher permitted torque. A maintenance reader uses it to find the right spare and to confirm that a replacement shares the same mounting footprint. Naming conventions vary between builders, and a helical gear motor manufacturer may print the ratio as a simple number or as a two-stage figure, so the code should always be read next to the ratio and torque fields rather than on its own. The duty note sets the time frame the other values apply to. IEC TS 60034-23 covers rated operating values and duty cycles as background for how a machine is expected to run, and that idea shows up on nameplates as a duty class or a note such as continuous duty. A drive rated for continuous running at a given torque can be pushed harder in short bursts, but a machine that runs loaded for long shifts belongs on the continuous rating. The mounting field matters just as much in daily work: foot-mounted, flange-mounted, and torque-arm units handle reaction forces differently, and a replacement that ignores the mounting line usually creates alignment or shaft-loading problems in its first week of running.
A nameplate on a helical gear motor is a set of linked operating limits, not a price tag or an order label. Power, output speed, torque, and ratio move together, so a single impressive number — whether it is kilowatts or newton metres — describes one point in the family rather than the capability of every unit. Duty and mounting notes complete the picture by saying how long those limits apply and how the unit is expected to sit in the machine. When a replacement is needed, matching output speed, permitted torque, ratio, and mounting form is what keeps the drive inside its rated window, and a helical geared motor distributor or supplier can usually confirm those fields against a specific model. Anyone who wants to see the full KC37 to KC187 envelope can review the KC series product data and compare fields side by side.
A：Torque on the nameplate is the turning effort the gear unit can pass through the output shaft without being overloaded, at the speed and duty stated on the same plate. It is usually given in N·m and is the figure that matters most for conveyors, mixers, and other driven machinery that resists turning. A torque value read without its matching output speed describes only part of the operating point, because torque and speed are linked through power.
A：Two KC series units with the same motor power can show different permitted torque because the torque at the output shaft depends on output speed and on frame size. A slower output turns the same power into more turning effort, and a larger frame such as KC187 carries heavier bearings and a thicker output shaft that can accept that load. Ratio choices inside the same frame also shift the output speed and therefore the torque the unit can deliver.
A：Not in the way people often expect. A higher ratio lowers output speed and, at the same input power, raises the torque available at the shaft, but the gear unit still has its own permitted torque limit that does not move with the ratio. Beyond that limit the gears, bearings, and output shaft are at risk. A very high ratio can also add a gear stage, which lowers efficiency slightly and adds heat, so the practical gain is smaller than the simple equation suggests.
Torque - Work done and Power Transmitted
