Overview Of Inverter Selection - Omron RX2 Series User Manual

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Overview of Inverter Selection

Motor Capacity Selection
Before selecting an inverter, first the motor should be chosen. In
selecting the motor, calculate the load inertia appropriate to the
application, and then calculate the required capacity and torque.
Simplified Selection Method (Required Output Calculation)
This method of calculation helps you select a motor by
calculating the output (kW) required by the motor to maintain
its steady rotations. To use this method for motor selection,
make allowance for the calculated result because it does not
include acceleration/deceleration and other transient state
calculations. The simplified selection method is suitable for
fan, conveyor, mixer, and other applications where a constant
state continues for a while.
* The simplified selection method cannot be used for the
following applications. For these applications, use the
detailed selection method.
• Those requiring rapid startup (acceleration).
• Those that frequently repeat run and stop.
• Those that have a large inertia at the power transfer part.
• Those that have an inefficient power transfer part.
For linear motion: Steady power P0 [kW]
M
Motor
* The same calculating formula is applicable to belt conveyors.
For rotation motion: Steady power P0 [kW]
Motor
Detailed Selection Method (RMS Calculation)
This method helps you select a motor by calculating the
effective torque and maximum torque values required to
achieve a certain pattern of operation for the application. It
selects a motor that is optimal for a particular operation
pattern.
Calculation of load inertia and motor-shaft conversion inertia
Depending on the type of the motor transfer system, calculate
the inertia for all parts and convert it into the motor-shaft
inertia.
• Example in hoist application
D
M
1
J
W
M
2
J
J
J
M
M
D
High-function General-purpose Inverter RX2 Series User's Manual
× 10
: Friction coefficient
: Mass of linear motion part [kg]
: Acceleration of gravity (g≈9.8 [m/s
: Speed of linear motion part [m/min]
: Efficiency of transfer part ( d1)
× 10
: Load torque (Load shaft) [N·m]
: Rotation speed of load shaft [r/min]
: Efficiency of transfer part ( d1)
2
J [kg·m ]
W
=J + J
1 2
2 2
M · D M · D
1 2
= + × 10
8 4
2
: Shaft conversion inertia [kg·m
W
: Inertia of cylinder (Shaft conversion) [kg·m
1
: Inertia of workpiece (Shaft conversion) [k·m
2
: Mass of cylinder [kg]
1
: Mass of workpiece [kg]
2
: Diameter of cylinder [mm]
Appendices A Technical Information
• Example in conveyor application
M
3
M
4
M
D M
2 2
J : Shaft conversion inertia (Cylinder-1-shaft conversion) [kg·m
W
J : Inertia of cylinder 1 (Cylinder-1-shaft conversion) [kg·m
1
J : Inertia of cylinder 2 (Cylinder-1-shaft conversion) [kg·m
2
J : Inertia of workpiece (Cylinder-1-shaft conversion) [kg·m
3
J : Inertia of belt (Cylinder-1-shaft conversion) [kg·m
4
M : Mass of cylinder 1 [kg]
1
M : Mass of cylinder 2 [kg]
2
M : Mass of workpiece [kg]
3
M : Mass of belt [kg]
4
D : Diameter of cylinder 1 [mm]
1
D : Diameter of cylinder 2 [mm]
2
• Example in roller application
–3
J
1
2
])
D J
2
M
J : Shaft conversion inertia (Roller-1-shaft conversion) [kg·m
W
J : Inertia of roller 1 (Roller-1-shaft conversion) [kg·m
1
J : Inertia of roller 2 (Roller-2-shaft conversion) [kg·m
2
M : Mass of workpiece [kg]
D : Diameter of roller 1 [mm]
1
–3
D : Diameter of roller 2 [mm]
2
• Example of conversion into motor-shaft inertia
2
J : [kg·m ]=J +G
L 1
J : Motor-shaft conversion inertia [kg·m
L
J : Load inertia (Load-side gear-shaft conversion) [kg·m
W
J : Inertia of motor-side gear [kg·m
1
J : Inertia of load-side gear [kg·m
2
Z : Number of motor-side gear teeth
–6
1
Z : Number of load-side gear teeth
2
] G : Gear ratio (Speed reduction ratio) = Z1 / Z2
2
]
2
]
2
J [kg·m ]
W
D
1
=J +J +J +J
1 2 3 4
2 2
M ·D M ·D
1 1 2 2
J
W
1
= + ·
8 8
2 2
M ·D M ·D
3 1 4 1
+ +
4 4
2
J [kg·m ]
W
D
1
2 2
D M·D
1 1
=J + J +
1 2
2
D 4
2
J
W
2
Load J
W
Load-side gear J
2
J Motor
L
Motor-side gear
J
1
2
(J +J )
2 W
2
]
2
]
2
]
2
D
1
2
D
2
–6
× 10
2
]
2
]
2
]
2
]
2
]
A
–6
× 10
2
]
2
]
2
]
2
]
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