Electrical Motor Sizing and Selection
Motor Sizing and Selection for Conveyor Drives
An undersized conveyor motor runs hot, trips on overload and shortens its own life. An oversized one costs more to buy, more to run every hour the line is on, and drags a larger drive, panel and cable along behind it. LVP Automation sizes and selects motors for conveyor and automation drives so the motor matches the duty the line actually has.
Sizing starts with the work the motor has to do: the mass being moved, belt or chain speed, any incline, the friction in the system, how quickly it has to reach speed, and how often it starts and stops through a shift. From there we work out the torque and speed needed at the gearbox output, the ratio to get there, and the motor and drive to suit, along with the conditions it has to survive in place, whether that is washdown, dust or heat. We are based in Finglas, Dublin 11 and work with customers across Ireland.
What Our Motor Sizing Service Covers
- Sized on Real Duty: We work from the load, speed, incline and start-stop pattern your line actually runs, not from whatever motor happened to be fitted before.
- Motor, Gearbox and Drive Together: The three are selected as one set, so the torque arrives at the shaft at the speed the line needs.
- Matched to the Environment: Washdown, dust, heat and duty cycle decide what will survive in place, so they form part of the selection rather than an afterthought.
- Right-Sized, Not Over-Sized: Oversizing wastes energy every hour the line runs and pulls a bigger drive, panel and cable along with it.
- Fewer Nuisance Trips: A motor sized for the real starting duty avoids the overload trips that come from asking a marginal motor to start a loaded belt.
- Support If the Line Changes: More load, a faster rate or a different product changes the sums. We can re-check the sizing rather than leave you to guess.
What we need in order to size a motor
Most of a sizing job is arithmetic once the inputs are known. The useful ones are:
- What is being moved, how heavy it is, and how much of it sits on the conveyor at once
- Line speed, and whether it needs to vary
- Any incline or decline, and whether the load can run back
- Conveyor type, length and construction, since that sets the friction and the moving mass
- How often the drive starts and stops, and how quickly it has to reach speed
- Hours run per day, and whether the load is steady or comes in surges
- Conditions on site: washdown, dust, heat, corrosives
- The supply and panel already in place, which limits what can be fitted without other changes
Where motor sizing usually goes wrong
Sizing on running load alone. A belt that turns comfortably once moving can need considerably more torque to break away loaded from standstill. Starting duty and inertia decide the motor as often as running load does.
Copying the old nameplate. Like-for-like replacement is only correct if the duty never changed. If the line runs faster, carries more, or handles a different product than it did when the motor was chosen, the original sizing no longer describes the job.
Ignoring starts per hour. Frequent starting is a thermal problem rather than a torque one. A motor with ample torque can still overheat if it is asked to start often enough.
Oversizing for safety. Fitting a larger motor than the duty needs does not buy reliability. It buys a higher purchase price, wasted energy for the life of the line, and a larger drive, panel and cable to go with it.
Related services
Motor selection rarely stands alone. Where a line is being designed or reworked, see conveyor system design. Where drives are controlled by a PLC and the acceleration and ramp times are set in software, see PLC programming. Drives and protection are fitted in the control panel, and a simulation package can test throughput and duty assumptions before anything is bought. If a motor has already failed, see electrical fault finding.
Common questions
Can you size a motor for a conveyor you did not build? Yes. Sizing depends on the duty and the mechanics, not on who supplied the equipment.
We only want a like-for-like replacement. Is sizing needed? If nothing about the line has changed, the original motor is a reasonable guide. If the line has been sped up, extended or given a heavier product since, the old nameplate describes a job the conveyor no longer does, and a replacement to the same spec inherits that mismatch.
Do you supply the motor as well as specify it? Motors and motion components are part of our product range, so we can supply as well as select. There is no obligation to buy the motor from us for us to size it.
Will a smaller motor cut our running costs? Only if the current one is genuinely oversized for the duty. Where it is, the saving is real and repeats every hour the line runs. Where it is not, fitting a smaller motor trades an energy saving for overload trips.
Where do you cover? We are based in Finglas, Dublin 11 and work with customers across Ireland.
Let's Connect
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