Panasonic M41A1G4L Operating Instructions Manual

Contents

– A-50 –Panasonic Corporation Electromechanical Control Business Divisionindustrial.panasonic.com/ac/e/ © Panasonic Corporation 2018 AQCTB02E 201806-E – A-51 –Panasonic Corporation Electromechanical Control Business Divisionindustrial.panasonic.com/ac/e/ © Panasonic Corporation 2018 AQCTB02E 201806-EChecking of permissible inertia loadWhen the load inertia J connected to the gear head is large, frequent starting of the motor or electromagneticbrake generates a large torque. If this impact is excessive, it may damage the gear head and the motor. Sinceinertia varies with types of the load, the tables on pages A-54 and A-55 describe how to calculate inertia ofdifferent shape loads. The inertia of the load significantly affects life expectancy of gear and electromagneticbrake. When applying the braking force by using the electromagnetic brake or brake unit, do not exceed apermissible load inertia set for a specific model.The permissible load inertia to a 3-phase motor is the inertia applied to the motor after it stops and then starts inthe opposite direction.• Find the load inertia to the motorshaft from the following formula.(SI units system)JM = JG xJG : Inertia of gear head output shaft (kg·cm 2)JM : Permissible inertia at motor shaft (kg·cm 2)i : Reduction ratio (e.g. 5 if the ratio is 1/5)* The formula also applies to GD 2 system.Motor and load inertiaThe equation of motion is described as below when the inertia load is driven by the motor.where,T : Torque (N·m)J : Moment of inertia (kg·m 2): Angular speed (rad/s)t : Time (s)n : Rotational speed (r/s)GD2 : Flywheel effect (GD2 = 4J)g : Gravitational acceleration = 9.8 (m/s2): Angular acceleration (rad/s 2)In the case of induction motor, torque generated at the starting varies depending on the speed. Therefore, anaverage acceleration torque is generally used, which is the averaged torque from the starting and the constantspeed.A necessary average acceleration torque T A to accelerate the load inertia of J (kg·cm2) (GD 2 (kgf·cm 2)) up to aspeed n (r/min) in time t (s) can be obtained by the following formula.• SI units • Gravitational system of unitsi21T = J = J · = · = · ·TA = x (N·m) T A = x (kgf·cm)ddt ddt dndt2π60GD24J9.55 x 104NtNtGD23750000GD 24To describe the moment of inertia, J and GD 2 is used. J is generally called inertia and has the same value ofphysical moment of inertia in SI units. Unit is in kg·m 2.GD2 (GD square) is called “flywheel effect” and generally used in industrial application with gravitational systemsof units. Unit is in kgf·m 2 or kgf·cm2. A relation between J and GD 2 is described as:J = GD2 / 4For the purpose of this document, both J for SI units and GD 2 for gravitational system of units are used. Unit of Jshould be kg·m 2 in dynamical significance, however, kg·cm 2 is used as well for convenience. Refer to pages A-54and A-55 for calculation of J and GD2 depending on the shape of the load.• Find the permissible load inertia moment at gearhead output shaft from the following formula.When reduction ratio is 1/3 to 1/50, JG = JM x i2When reduction ratio is 1/60 or larger,JG = JM x 2500JG : Permissible load inertia moment at gear head outputshaft (kg·cm2)J M : Permissible inertia at motor shaft (kg·cm 2)i : Reduction ratio (e.g. 5 if the ratio is 1/5)Permissible inertia (J M) at motor shaft varies with motors.To find the inertia for the motor in question, refer to tableson pages A-52 and A-53.InertiaMotor selection