Page 237 - Demo

V012024 • © 2024 Portescap. Specifications subject to change without notice.Examples of Can Stack Step Motor calculationsExample: Drive with a Can Stack Step Motor with a frictional torque loadFor this application we will consider a Step Motor for an intermittent duty application. The application requirements are: Available voltage: 24 Vdc Available current: 2 Amp Motor operating point: 67.5° [θ] desired motor position 15 mNm [τ] desired motor torque 0.06 [∆t] desired move time Intermittent operationIf a 7.5° per step motor is used, then the motor would have to take nine steps to move 67.5°. 67.5°/7.5° = 9 steps f = step rate = 9 steps/0.06 sec = 150 steps/sIn the figure below the maximum pull-in rate with a torque of 15 mNm is 275 steps/s. We use the pull-in torque curve for this calculation because the control circuit does not provide any ramping. The maximum speed the motor can reach during operation is limited by the maximum speed the motor can start at without missing any steps. This is what the pull-in torque curve represents.The problem is now solved. The Can Stack motor 42M048C1U motor could be used at 150 steps/s because this point falls well below the pull-in torque curve.Use the pull-out torque curve in conjunction with a Torque = Inertia × Acceleration (τ = J × α) analysis when the load is inertial and/or acceleration control is provided.In this equation acceleration or ramping is in rad/s2 α = ∆ω/∆t = rad/s2Ramping:Acceleration control or ramping is normally accomplished by gating on a voltage controlled oscillator (VCO) and the associated charging capacitor. Varying the RC time constant will give different ramping times. A typical VCO acceleration control frequency plot for an incremental movement with equal acceleration and deceleration time would be as shown below.0.005.0010.0015.0020.0025.0030.0035.0040.00012345650 100 150 200 250 300 350 40062.5 125 187.5 250 312.5 375 437.5 500 rpmpps42M048C1U Torque vs Speed5 vdc, full step, unipolar voltage drive 42M048C1U 42M048C1U Pull-Out Torque Pull-In Torqueoz in mNmRUN RATE∆t RUNTIME IN M SEC∆t ACCEL ∆t DECEL237