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Magnetic Lifting Machine Application


Definition

A lifting machine (figure 1) is a magnetized set of steel components that act as electromagnets to lift large metallic objects such as scrap metal or steel plates. Permanent Magnetic Lifters are mainly used to lift steel plates, blocks, press mold etc. and load / unload in machines during handling operation. They can hoist moving iron blocks and other magnetic materials. They are easy to operate and safe to handle and hence are widely used as lifting devices in factories, docks, warehouses and transportation industries. By using them, working condition can be improved and working efficiency can be increased.

Magnetic Lifting Machine          Magnetic Lifting Machine

Figure 1 - Magnetic Lifting Machine Description

This example consists of a magnetostatic analysis of a lifting machine (Figure 2) composed of magnetized steel lifting, a steel plate and a small distance from the magnet. The machine is magnetized using a wound coil with a current excitation. EMS from EMWorks has been used to compute the magnetic flux in the machine, as well as the force applied on the steel plate.

3D Model of the Magnetic Lifting Machine
Figure 2 - 3D Model of the Magnetic Lifting Machine

Study

The Magnetostatic module of EMS is used to compute and visualize the magnetic flux and the magnetic intensity in the coil, in the steel lifting, in the steel plate and in the air gap between them. It is also used to calculate the inductance of the coil and the electromagnetic force applied in the load (the steel plate). After creating a Magnetostatic study in EMS, four important steps shall always be followed: 1 - apply the proper materials for all solid bodies, 2- apply the necessary boundary conditions, or the so called Loads/Restraints in EMS, 3 - mesh the entire model and 4- run the solver.

 

Materials

For the Magnetostatic study the main property we need is the relative permeability of  each material (Table 1). 

Components / Bodies Material Relative  Permeability
Coil 1   Copper 0.99991
Coil 2   Copper 0.99991
Air Box Air 1
Core 1 AISI 1008 Steel Non linear
Core 2 AISI 1008 Steel Non linear
Cover 1 AISI 1008 Steel Non linear
Load Typical Steel Non linear
Central Plate 1 AISI 1008 Steel Non linear
Central Plate 2 AISI 1008 Steel Non linear
lateral Plate 1 AISI 1008 Steel Non linear
lateral Plate 2 AISI 1008 Steel Non linear
Cote 1 AISI 1008 Steel Non linear
Cote 2 AISI 1008 Steel Non linear

Table1 - Table of materials

The Typical Steel and the AISI 1008 Steel (Figure 3) have a non linear isotropic relative permeability. In EMS Materials Library, there is an entire folder for  non linear materials where BH curves can be found.

BH Curve of  Typical Steel and AISI 1008 Steel
BH Curve of  Typical Steel and AISI 1008 Steel
Figure 3 - BH Curve of  Typical Steel and AISI 1008 Steel
 

Loads and Restraints

Loads and restraints are necessary to define the electric and magnetic environment of the model. The results of analysis directly depend on the specified loads and restraints. Loads and restraints are applied to geometric entities as features that are fully associative to geometry and automatically adjusted to geometric changes.
In this study, a coil (Table 2) is applied and the Steel plate as a Load (Table 3) where we need to calculate the virtual work.

Name Number of turns Magnitude
Wound Coil 1 6000 5 A
Wound Coil 2 6000 5 A
 
Table 2 - Coils information
 
Name Torque Center Components / Bodies
Virtual Work At origin Load
 
Table 3 -  Force and Torque information
 

Meshing

Meshing is a very crucial step in the design analysis. EMS estimates a global element size for the model taking into consideration its volume, surface area, and other geometric details. The size of the generated mesh (number of nodes and elements) depends on the geometry and dimensions of the model, element size, mesh tolerance, and mesh control. In the early stages of design analysis where approximate results may suffice, larger element size can be specified for a faster solution. For a more accurate solution, a smaller element size may be required.
Mesh quality can be adjusted using Mesh Control (Table 4), which can be applied on solid bodies and faces. Below (Figure 4) is the meshed model after using Mesh Controls.
 
Name Mesh size Components /Bodies
Mesh control 1 30.00 mm Load

Table 4 - Mesh control


Meshed Model
 
Figure 4 - Meshed Model
 

Results

After running the simulation the following results have been obtained: Magnetic Flux Density (Figure 5, 6), Magnetic Field Intensity, Applied Current Density (Figure 7), Force density, Field Operations (B and H derivatives) and a result table which contains the computed parameters of the model (Figure 8 ), force and torque values (Table 5, 6).
 
Magnetic Flux Density fringe plot
 
Figure 5 - Magnetic Flux Density fringe plot


Magnetic Flux Density vector plot

Figure 6 - Magnetic Flux Density vector plot

Applied Current Density in the two coils, vector plot

Figure 7 - Applied Current Density in the two coils, vector plot

 
  Fx-axis (N) Fy-axis (N) Fz-axis (N)
Virtual work 1 -9.252253e+001
 
9.843460e+003 2.304053e+001
 
Table 5 -  Force results
 
  Tx-axis (N.m) Ty-axis (N.m) Tz-axis (N.m)
Virtual work 1 4.111047e+003 4.662479e+001 -5.6221182e+001
       
Table 6 - Torque results
 
Results Table
Figure 8 - Results Table
 

Conclusion

The Magnetostatic module of EMS gives all needed results of a Magnetic Lifting Machine for a good dimensioning and better efficiency. EMS is, an addition of being fully integrated in Solidworks and Autodesk Inventor, accurate, intuitive and easy to use.