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V012024 • © 2024 Portescap. Specifications subject to change without notice.Torque [oz-in]Speed (rpm)Torque [mNm]Max. continuous operation at 25°C20W35W50W80W65W0 1.0 2.0 3.0 4.0020,00010,00030,00040,00050,00015,0005,00025,00035,00045,0000 10 20 30ContinuousShort timeExamples of BLDC Slotless Motor calculationsThis chapter aims to provide all the information necessary to select a BLDC Slotless motor and to calculate the values at the desired operating point. The following examples are for motor applications running in continuous operation.1) Example: Brushless application requirementsFor this application we are looking for a BLDC motor with high speed capabilities in a continuous duty operation. The motor will be controlled by an amplifier for a motor with Hall Effect sensors. Available voltage: 30 Vdc Available current: 3 Amps Motor operating point: 12,000 rpm [ω] desired motor speed 20 mNm [τ] motor shaft output torque 22° C [Tamb] ambient temperature Continuous operation Motor physical dimensions: 60 mm maximum allowable length 25 mm maximum allowable diameterUsing the speed-torque curve and maximum allowable operating specifications from the data sheet, it is possible to select the correct motor solution. Here we find the BLDC motor 22ECP45 capable of operating at the desired working point. The motor 22ECP45 is available in 2 different 24 Vdc windings. Windings offer same overall performance (maximum torque, merit factor, etc...) but help using different voltage and current configurations. Since the desired motor speed is 12,000 rpm we will investigate the \with a no load speed of 15,700 rpm. The torque constant is 14.6 mNm/A and the resistance is 1.59 Ω.Calculating for the motor current we find: I = τ /k + I0= 20 mNm / 14.6 mNm/A + 60 mA = 1.43 AThe supply current of the system is 3 Amps and therefore current draw is not an issue. Calculating the voltage required to run the motor at 12,000 rpm: U = R × I + k × ω ω = 2π/60 × n = 2π/60 rad/rpm-s × 12,000 rpm = 1257 rad/s U = 1.59 Ω × 1.43 A + (14.6 × 10−3 Nm/A) × 1257 rad/s = 20.6 VdcThe problem is now solved. Since the voltage required is less than the available voltage, it is possible to reach the operating point with the BLDC Slotless motor 22ECP45 8B 82 .01. The 22ECP45 with coil \ same working point, would have required higher voltage but lower current. 230Engineer’s Appendix