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.
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.
Figure 2 - 3D Model of the Magnetic Lifting Machine
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.
For the Magnetostatic study the main property we need is the relative permeability of each material (Table 1).
|Components / Bodies||Material||Relative Permeability|
|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.
Figure 3 - BH Curve of Typical Steel and AISI 1008 Steel
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|
|Name||Torque Center||Components / Bodies|
|Virtual Work||At origin||Load|
|Name||Mesh size||Components /Bodies|
|Mesh control 1||30.00 mm||Load|
|Fx-axis (N)||Fy-axis (N)||Fz-axis (N)|
|Virtual work 1||-9.252253e+001
|Tx-axis (N.m)||Ty-axis (N.m)||Tz-axis (N.m)|
|Virtual work 1||4.111047e+003||4.662479e+001||-5.6221182e+001|