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V012024 • © 2024 Portescap. Specifications subject to change without notice.2) Example: Brushless motor with a GearheadFor this application we want to drive a load at an extremely low constant speed. The customer needs a combination of a Brushless DC motor with a gearhead. Available voltage: 20 Vdc Available current: 2 Amps Gearmotor operating point: 60 rpm [ω] desired gearmotor speed 150 mNm [τ] gearmotor shaft output torque 22° C [Tamb] ambient temperature Continuous operation Motor physical dimensions: 120 mm maximum allowable length 20 mm maximum allowable diameterBefore selecting a motor we must first determine which gearhead is suitable for the application. The important parameters are the specifications relating to the operating point at the shaft of the gearhead. Once an appropriate gearhead has been determined, the working point at the motor shaft can be calculated. From here the motor type can be defined using the same procedure as in the previous example for motor only.We start the elimination process by comparing the desired gearhead output torque with the data of the various gearheads in continuous operation as listed in the catalog specification pages. We find the R16 planetary gearhead (16 mm diameter) capable of operating at the desired working point.For continuous operation, one of the most important gearhead parameters to be considered is the maximum recommended input speed into the gearhead (nmax input-gearhead). This specification allows us to calculate the maximum reduction ratio (imax) to use for the application. imax = nmax input – gearhead / noutput – gearhead = 7,500 rpm / 60 rpm = 125The gearhead can be chosen by selecting the largest available ratio that is below the above result. By reviewing the catalog we choose the 121:1 ratio R16 gearhead.Motor speed at the shaft: nmotor = i × noutput – gearhead = 121 × 60 rpm = 7,260 rpm Motor torque at the shaft: η = 0.65 (gearhead efficiency) τ motor = τ gearhead /i × η = 150 mNm/(121 × .65) = 1.91 mNmM (Nm)Continuous working rangeTemporary working rangeValues at the output shaftn (rpm) Dynamic torque0.2 0.4 0.6 0.8 1M (Nm)Continuous working rangeTemporary working rangeValues at the output shaftn (rpm) Dynamic torque0.2 0.4 0.6 0.8 1231