Calculating Linear Motor Requirements - Baldor …

1 J-16AC MotorsAC ControlsMotionControlsOverview DC MotorsDC ControlsSoftwareLinearStagesLinearMotors EngineeringInformationCalculating Linear Motor RequirementsIn order to determine the correct Motor for a particularapplication it is necessary to be familiar with thefollowing OF MOTIONB asic kinematic equation: xo+ vot = at2/2a = acceleration (g s)x = stroke (inch [m])t = time (seconds)v = velocity (in/sec [m/sec])g = gravitational acceleration (in/sec2[m/sec2])A trapezoidal velocity profile is common with linearmotors and the basic kinematic equation can bemanipulated to yield results based on what is time and stroke are known:When time and velocity are known:When velocity and stroke are known:Another common velocity profile associated with linearmotors is the triangular velocity profile.

2 As before, thebasic kinematic equation can be manipulated to solvefor this time and stroke are known:NEWTON S SECOND LAWN ewton s Second Law provides a simple method ofconverting between forces, payloads, andaccelerations. It states:EnglishMetricF = maF = magwhere,F = ForceLbsNm = payloadLbskga = accelerationg sg sg = gravitational accel386 m/sec2 EnglishMetrica =2xa =2x386 t2a =va =v386 ta =v2a =v2386 (2x) (2x)vtEnglishMetrica =4xa =4x386 t2 Example: Calculate the acceleration required to getto move 1 in ( m) in =4 x 1a = 4 x ( ) ( )2a = g sa = g s vtExample:Calculate the acceleration required to getto 200 in/sec [ m/sec] in =20a = = g sa = g sExample.

3 Calculate the force required to acceleratea Lbs [ kg] payload horizontally at g sEnglishMetricF = x = x x = LbsF = NJ-17AC MotorsAC ControlsMotionControlsOverview DC MotorsDC ControlsSoftwareLinearStagesLinearMotors EngineeringInformationDUTY CYCLEThe duty cycle of a Motor is defined as the time themotor receives power during a cycle divided by the totaltime of the cycle. When a Linear Motor receives powerfor more than thirty (30) seconds, it is operating at aduty cycle of 100%.Because duty cycles less than 100% allow time for themotor to cool, a lower duty cycle allows all linearmotors, except steppers, to be run with more thanthree times their continuous current rating for a shortperiod of time.

4 Since force is proportional to current,motors operating at lower duty cycles can producehigher forces than when run CONTINUOUS FORCEThe relation between the rated continuous force amotor can deliver and the effective continuous force it iscapable of providing at a lower duty cycle is: Linear Motor SELECTION PROCESSF ollowing is the selection process for an application thatrequires a cog-free brushless Linear Motor . The firstsection provides customer Requirements . The secondsection provides the calculations that are necessary tomake the Motor selection. That last sectiondemonstrates the effect of reducing duty cycle andacceleration on Motor REQUIREMENTSA pplicationOptical inspection (movinga single-axis optics carriage assembly)Stroke60 in [ m]Duty Cycle100%Payload40 Lbs.

5 [ kg]Resolution3 micron customer-supplied encoderLoad supportCustomer-supplied bearingsMotion ProfileLow force ripple required. Payload must move full stroke in :During one cycle of operation a motoris on for 1 sec and off for 3 sec. What is the dutycycle of the Motor for these conditions?Duty Cycle =1 x 100% = 25%1 + 3Fc= F Fc= continuous = force at specifiedduty specified dutycycle%% Example:Calculate the effective continuous forceof a Motor that provides 197 Lbs [877 N] of force ata 30% duty cycle. EnglishMetricF30= 197 = 30%F30= 877 = 30FC= 197 = 108 LbsFC= 877 = 480 EnglishMetrica =4 x a = 4 x 386 =4 x 60a =4 x x ( ) x ( )2a = g sa = g sDuty Cycle =time on x100%time on + time offLinear MotorsJ-18AC MotorsAC ControlsMotionControlsOverview DC MotorsDC ControlsSoftwareLinearStagesLinearMotors EngineeringInformationCALCULATIONSA cceleration and force must be calculated to select theappropriate Linear Motor .

6 Acceleration is calculated withthe following formula:Force in calculated with the following formula:F = maF = magso,F = 40 x = = LbsF = 137 NMOTOR SELECTIONThe Linear Motor that best meets the applicationrequirements is the cog-free brushless Linear motormodel # LMCF08D. This Motor s continuous force is 33 Lbs. [147N] and has a maximum acceleration at this100% duty cycle of g OF LOWER DUTY CYCLESU sing Newton s Second Law and leaving the payloadunchanged, what acceleration is the LMCF08D motorcapable of when operated at a 30% duty cycle?Leaving the acceleration unchanged, what LMCF08 Dpayload is the Motor capable of moving when operatedat 30% duty cycle?

7 A reduction of duty cycle from 100% to 30% allows theLMCF08D Motor to go from an acceleration of g sto g s and from a payload of 40 Lbs [ ] Lbs [ kg]. Both improvements cannot berealized simultaneously using the LMCF08D a larger Motor is needed or the requirementsmust be examined to determine which parameter Requirements CHANGEWhat Motor best meets the following Requirements ?Duty Cycle = 30%Payload = 40 Lbs [ kg]Acceleration = g sSince this is at a 30% duty cycle, the continuous forcemust be LMCF06D has a continuous force of Lbs. [110N]and meets the acceleration and payload requirementsof this FC100 FDC= FC100 DCDCF30= 33 100F30= 147 1005050F30= LbsF30= N m = 40 Lbsm = kg g = ma30F30- ma30ga30= F30a30= F30mmg= X g sa 30= g s Fc= 36Fc= 1601001003030Fc= LbsFc= EnglishMetricF30= LbsF30= N mm = Lbsm = g s g = m30aF30- m30aga30= F30a30= F30aag= X Lbsm 30= kgEnglishMetricF = maF = magso.

8 F = 40 x = x x = 36 LbsF = 160 NLinear MotorsLinear MotorsJ-19AC MotorsAC ControlsMotionControlsOverview DC MotorsDC ControlsSoftwareLinearStagesLinearMotors EngineeringInformationLinear Motor Requirement SheetPage 1 of 4 Company _____Date _____Contact _____E-Mail_____Title _____Phone _____Address_____Fax _____Address _____Industry _____City _____Distributor _____State, Zip _____District Office _____Describe the application and what you are trying to accomplish:Salesperson _____Estimated quantity needed _____ Need: Immediate within 6 months within 12 months over 1 yearPlease provide as complete as possible.

9 A) Motor Type Preferred Don t KnowServo - Closed loop Brushless Cog-free, no magnetic attraction Brushless Iron-core BrushStepper - Open Loop Single Axis Dual Axis w/Air BearingLight Load, Short Stoke Applications Moving Coil - Customer Supplied Bearing Moving MagnetAC Induction Linear Induction Open Closed Loop Polynoid - open loop, low duty cycleB) Stage Type Preferred Don t KnowSingle Bearing - open construction w/5 micron encoder standard w/1 micron encoder optionalExtruded - industrial w/5 micron encoder standardEnclosed - precision w/5 micron encoder standard w/1 micron encoder optionalCross-roller - high precision w/5 micron encoder standard w/1 micron encoder optionalAir Bearing on Granite highest precisionL Stage highest precision micron encoder standard micron encoder optional w/1 micron encoder optionalC)

10 Voltage Available 115 VAC Single Phase 230 VAC Single Phase 230 VAC Three Phase 460 VAC Three PhaseLinear Induction MotorsNOTE:Higher speeds requirehigher ) Environment _____ Degrees F _____ Degrees C Dusty Gritty E) Mounting Horizontal - Table Horizontal - Wall Vertical with_____% Counterbalance Angled at _____ DegreesF) Position Resolution None Required 10 Micron = inch 5 Micron = inch 1 Micron = inch Other Stepper Repeatability ofG) Quote Additional Trap Amplifier - for point to point moves Sine Amplifier - for contouring moves Stepper Indexer Driver Motion Controller for _____# of axes Stand Alone PC-based Linear Encoder w/resolution from above Motor Power & Hall Cable Length H)