General application of constant magnets (CM) in an array of electrical and mechanical engineering products led to a necessity of CM magnetization either as a part of those products and singular immediately before setting up. By magnetization is meant a process, which makes magnetic material intensity of magnetism grow by external magnetic field effect [1] and magnetization vectors reorientation of magnetic material towards applied field direction; and which includes rotation, moving and para processes. Maker could magnetize CM, but more often, it is preferred to deliver magnets in non-magnetized condition, magnetize them immediately before installation, or being a part of a product, it requires special way of magnetization. There are several reasons [2] for CM magnetization at the assembly location:

- it is hard or impossible to assemble required product with integral magnetized CM because of attraction or repulsion between magnets and still elements;

- during transportation, translocation CM can effect on or even destroy the things around, for example, credit cards, watches, electronic devices, etc.;

- large-size CM or in pack can cause the injury to the worker by attraction between magnets and metal surfaces;

- CM can effect on navigation aids, especially in the aircraft, so it demands legislative regulation of magnets delivery;

- magnetized CM may grab trash with metallic inclusions, like swarf, powder, etc. It is difficult to remove them, and requires special tools and actions;

- manufacture of the product, which includes CM or the whole CM construction, needs to control magnetizing process to achieve required magnetic density modulation in front gap (electrical machine, focusing system) for parameter setting by affecting on the intensity of CM magnetization (electromagnetic relay);

- regulation (calibration measurement) of different schedule line or different manufacture CM to conform them with preset tolerance, because they may have distinction in parameters (surface induction, attraction force, etc.);

- complicated types of magnetizing of CM different forms.

Therefore, magnetizers meant to solve listed above problems, and provides required direction and sufficient magnitude of magnetic field in working members (magnet coil, inductor system) for CM magnetization until induction saturation. Mainly there are two types of magnetizers in industrial application: DC electrical magnets and impulse excitation machines.

 

Electrical magnets, pic.1, used to magnetize particular CM with low-level coercitive force HcJ (ЮНДК, barium ferrite, strontium ferrite) without the need for complicated type of magnetization. Most often, they produce magnets in accordance with requirements of factory, which applies given class of CM in its products.

Impulse excitation machines (IEM) became widely used to magnetize CM for the almost full range of application in the products of Russian and foreign industry. Impulse excitation machines accumulate energy in the bank of capacitor for definite time (from a slit of second to tens of seconds), depending on the energy store charge voltage and capacity of the capacitor bank, so they give up energy during the short period of discharging ≤ (10÷15)·10-3с. That is why the heavy current of consumption is not required for high-power pulse, so it permits to use monophase network 220 V. The ability to magnetize modern high-coertivity CM (NdFeB, Sm2Co17, SmCo5), reasonable size (taking into account storage density) and the relative simplicity of equipment we may designate as advantages.

 

Pic.2 Impulse excitation machine electric circuit diagram: а) without pulse transformer; б) with pulse transformer

Mostly there are two hardware versions of IEM: with and without pulse transformer. Such division is conditional, because the applied pulse current source includes charging device, high-voltage rectifier, energy store, power-commutating switch and actuating, control and regulating system, though it is one unit. On the pic.2 two hardware versions of impulse excitation machine electric circuit diagram showed. “Classic” magnetizer pulse current source construct showed on pic.3 [6]. The pulse transformer with the inductor clamp device placed inside worktable and connected with the machine power leads. Nevertheless, working members (inductor systems) meant for magnet field generation of those two types IEM have fundamental difference and they are not interchangeable.

Pic.3 Magnetizer pulse current source construct

The pulse transformer construction with single-turn winding, spun of flat copper, which blanket primary heavy winding, found practical application. Required configuration single-turn systems applied as a working inductor in IEM with transformer, pic.4 [4].

Pic.4 Samples of single-turn coils (without dielectric fixing bracket)

 

The IEM with pulse transformer and single-turn coil systems as better described in [3]. The IEM without pulse transformer complete with multiturn coil systems and various design solenoids, which connected directly to power leads of the machine. Such systems line is wide range and solves similar problems in CM magnetization as single-turn one [3]. CM basic forms and magnetization types showed in pic. 5 [5].

 

Pic.5 Basic CM forms and magnetization types

 

Circuit and hardware solutions in pulse magnetization machines formed today in general and differ in control settings, magnetizing process control and CM tests recording. Inductor systems issues are still actual today and demand determined engineering in certain scenarios. In the design of inductor systems, a set of following conditions should be observe:

- Inductor systems (IS) when couple with IEM should support enough magnetic strength for CM saturation;

- CM should stay retain in holder-adapter and not move during magnetization and further removal from IS working zone;

- IS winding should be durable enough to stand mechanical loading during pulse current flow. It is true for insulation material and applied;

- IS heating resistance. Windings temperature rises rather sudden to carry away heat even trough thin insulation coat. A pulse train can lead to critical heating of the IS winding and insulation breakdown. It is necessary if relevant to provide forced-feed rejection of heat and control IS temperature;

- IS should be safe while working and should not damage the operator and equipment around.

The success in engineering, production and further service of magnetizing equipment provided by KBEA specialist’s qualification and many years’ experience in this field.

 

 

References: 

1. ГОСТ 19693-74 Материалы магнитные. Термины и определения;

2. Joseph J. Stupak Jr., Methods of Magnetizing Permanent Magnets, Oersted Technology Corp.,2000;

3. Нестерин В.А. Оборудование для импульсного намагничивания и контроля постоянных магнитов,-М.: Энергоатомиздат,1986.

4. Нестерин, В.А. Компоненты интеллектуальных мехатронных модулей/ В.А. Нестерин, Е.В. Волокитина.- Чебоксары, 2014.

5. http://kbea.ru

6. http://www.chuvsu.ru/~emtep/pm.html