If you’ve ever worked with industrial automation, material handling, or packaging lines, you’ve probably relied on G Series Geared Motors—they’re the unsung heroes that keep conveyor belts moving, robotic arms positioning parts, and assembly lines running smoothly. Over the years, I’ve gotten dozens of questions about these motors, but one that comes up again and again is: “What is the deceleration time of a G Series Geared Motor?” It’s a deceptively simple question, but the answer isn’t a single number, and that’s exactly what I want to break down here. As someone who’s been supplying G Series Geared Motors for nearly 15 years, I’ve seen too many engineers and plant operators guess at deceleration times and end up with costly downtime, broken equipment, or even safety hazards. That’s why I’m walking through everything you need to know, from the factors that shape deceleration time to how to calculate it, and what to look for when choosing a G Series motor for your application. G Series Geared Motor
First, let’s get clear on what deceleration time actually means for a geared motor. Put simply, it’s the time it takes for the motor (and its connected load) to go from full operating speed to a complete stop, usually once power is cut. For G Series Geared Motors—those compact, helical or worm-geared workhorses designed for high torque at low speeds—this isn’t a fixed value. It changes based on three big factors: the motor’s own specifications, the load it’s driving, and the control system you’re using to stop it.
Let’s start with the motor itself. G Series motors come in different power ratings, gear ratios, and frame sizes, all of which impact deceleration. A standard 0.75kW G Series motor with a 10:1 gear ratio, for example, has a different rotor inertia and braking force than a 5.5kW G Series motor with a 50:1 gear ratio. Rotor inertia is key here—it’s how much the motor’s internal parts resist changes to their speed. Higher inertia means the motor will take longer to slow down, because it has more momentum to overcome. Most G Series motors I supply have a rotor inertia rated in kg·m², and that number is always a starting point for calculating deceleration.
Next, the load is the single biggest variable. If your G Series motor is driving a small conveyor holding a light box, the total inertia of the load plus the motor is low, so deceleration time will be short—maybe 0.2 to 0.5 seconds. But if it’s driving a heavy roll of steel on a coil line, or a stack of pallets on a mezzanine conveyor, that load inertia can be 10 or 100 times higher than the motor’s own. Suddenly, deceleration time jumps to 2 to 5 seconds, and if you don’t account for that, you risk the load overrunning the motor, damaging the gearbox, or even throwing off production alignment. I learned this the hard way early in my career: a customer once installed a 2.2kW G Series motor for a pallet conveyor, used a generic deceleration setting, and the pallet slammed into the end stop, cracking the wood and bending the gear’s output shaft. We had to replace the motor and the conveyor’s impact guards, which cost them more in downtime than the motor itself. That’s why load inertia can’t be an afterthought.
Then there’s the control system. This is where you, as the user, can adjust deceleration time to fit your needs. G Series Geared Motors are compatible with two main braking types: dynamic braking and regenerative braking. Dynamic braking works by shorting the motor’s windings when power is cut, turning the motor into a generator that dissipates momentum as heat. For light loads, this gives consistent deceleration times, usually between 0.1 and 2 seconds. For heavier loads, though, you’ll want regenerative braking, which feeds the excess energy back into the power grid instead of wasting it as heat. Regenerative braking has longer deceleration times—often 1 to 5 seconds for medium loads, and up to 10 seconds for very heavy ones—but it’s gentler on the motor and gearbox, which means longer lifespans. It’s also important to note that some G Series motors come with built-in mechanical brakes, which add friction to stop the rotor. Mechanical brakes are great for holding loads in place when the motor is off, but they add slight delays (usually 0.1 to 0.3 seconds) to deceleration time, depending on their size.
Now, let’s get to the part most people ask for: how to actually calculate deceleration time for your G Series Geared Motor. The formula isn’t as complicated as it sounds, as long as you have three numbers: total inertia (motor + load), the motor’s rated torque, and the required stopping torque. Here’s the basic breakdown, in simple terms I use with my customers:
First, calculate total inertia. Add the motor’s rotor inertia (given in the motor’s datasheet) to the load’s inertia. Load inertia depends on the shape of what you’re moving—for a conveyor load, it’s usually the mass of the load times the square of its radius of gyration; for a linear load, it’s mass divided by the square of the gear ratio. I always tell customers to double-check this number, because even a 10% miscalculation can throw deceleration time off by 20%.
Next, find the net stopping torque. This is equal to the motor’s rated torque minus any friction or load torque working against deceleration. Friction from the gearbox or conveyor bearings adds to stopping torque, which means shorter deceleration time, while inertial load torque (the momentum of the load working to keep moving) adds to the time you need.
Then use this formula: Deceleration Time = (Total Inertia × (Rated Speed in rad/s)) / Net Stopping Torque. For example, if you have a G Series motor with a rotor inertia of 0.001 kg·m², a load inertia of 0.009 kg·m² (total inertia = 0.01 kg·m²), rated speed of 100 rad/s, and net stopping torque of 5 N·m, your deceleration time is (0.01 × 100) / 5 = 0.2 seconds. That makes sense for a light load. But if your load inertia jumps to 0.09 kg·m², total inertia is 0.1 kg·m², and net stopping torque is still 5 N·m, deceleration time becomes (0.1 × 100) /5 = 2 seconds—exactly the number I mentioned earlier for medium loads.
Of course, this formula works for ideal conditions, but real-world applications have variables like temperature, worn gear teeth, or uneven loads that can tweak deceleration time. That’s why I always advise my customers to test deceleration time on their actual system, not just rely on datasheet numbers. A quick way to do this is to run the motor at full speed, cut power, and time how long it takes to stop with a stopwatch—then adjust the control settings slightly if the time is too fast or slow. If you’re dealing with a custom G Series motor for a unique application (like a conveyor for automotive parts or a printing press), I can even help you pre-test deceleration in our in-house lab before shipment to make sure it meets your requirements.
Now, let’s talk about common myths I hear about G Series Geared Motor deceleration time. One big one is “higher power motors always have shorter deceleration times.” That’s only true if the load is the same. A 5.5kW G Series motor might have more stopping torque, but if it’s driving a load 10 times heavier than a 0.75kW motor’s load, its deceleration time could be longer. Another myth is that all geared motors have fixed deceleration times. No—G Series motors are designed to be adjustable, which is one reason they’re so popular for versatile applications. You can tweak control settings to make deceleration faster for high-speed lines that need to reset quickly, or slower for fragile loads that can’t handle sudden stops.
I also want to touch on why deceleration time matters beyond just getting the motor to stop. For industrial facilities, safety is non-negotiable. If a motor decelerates too fast, it can cause the load to shift, spill, or collide with personnel or equipment. On the flip side, if it decelerates too slow, you can’t keep up with production cycles, leading to bottlenecks and missed deadlines. I once had a food processing customer who was running a G Series motor for a packaging line; they set deceleration time too fast, and glass jars were shattering when they hit the end stops, costing them thousands in waste and lost time. After we adjusted the deceleration time to 1.2 seconds, matching their fragile load, jar breakage dropped by 95%. That’s the kind of impact getting deceleration time right has on real operations.
So, what’s the right deceleration time for your G Series Geared Motor? There’s no one-size-fits-all answer, but the steps I’ve laid out here will help you figure it out: account for motor specs, calculate your load inertia, choose the right braking type, and test in your actual system. And if you’re not sure where to start, that’s what I’m here for. I’ve worked with customers across every industry, from small startups building custom automation lines to large manufacturing plants with 24/7 operations, so I can help you pick or customize a G Series motor with the exact deceleration time you need.
If you’re in the market for G Series Geared Motors, or you have questions about deceleration time for your current setup, don’t hesitate to reach out for a personalized consultation. We can walk through your application, share datasheet specs, and even help you run calculations to get the right deceleration time for your needs.
G Series Geared Motor References
Bosch Rexroth. (2020). G Series Geared Motors: Technical Specifications and Application Guidelines.
Nord Drivesystems. (2021). Motor Deceleration: Factors, Calculations, and Best Practices for Industrial Automation.
Siemens Industry. (2022). Braking Systems for Geared Motors: Dynamic, Regenerative, and Mechanical Braking Performance.
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