=Paper=
{{Paper
|id=Vol-2744/short41
|storemode=property
|title=Calculation of the Energy of Capacitors for a Spot Welding Apparatus by a Numerical Method (short paper)
|pdfUrl=https://ceur-ws.org/Vol-2744/short41.pdf
|volume=Vol-2744
|authors=Sergei Zuev,Dmitry Varlamov,Anatoly Fironov,Alexander Kanareykin,Аrtem Timoshenko,Alexander Shvecov,Vitaly Kuksa
}}
==Calculation of the Energy of Capacitors for a Spot Welding Apparatus by a Numerical Method (short paper)==
https://ceur-ws.org/Vol-2744/short41.pdf
Calculation of the Energy of Capacitors for a Spot
Welding Apparatus by a Numerical Method*
Sergei Zuev[0000-0001-7033-1882], Dmitry Varlamov[0000-0002-7742-5037], Anatoly Fironov[0000-
0003-2683-9958]
, Alexander Kanareykin[0000-0002-9267-9254], Аrtem Timoshenko[0000-0002-5559-
6900]
, Alexander Shvecov[0000-0002-4840-7542], Vitaly Kuksa[0000-0002-4667-4639]
Moscow Polytechnic University, 432700, 38 Bolshaya Semenovskaya,
Moscow, Russia
sergei_zuev@mail.ru, varlamovd@mail.ru,
fironov@amfconsulting.ru, knsalex@yandex.ru,
prokypt@gmail.com,aleksander55_94@mail.ru,
ya.vetal11@yandex.ru
Abstract. This article provides information on the development of an adjustable
spot welder implemented on the basis of the capacitor principle without a trans-
former. Also the scientific work considers the calculation of the energy of the
capacitors for a spot welding apparatus using modern methods of numerical
simulation and programming. The method of calculation is given, as well as a
mathematical solution tool. The calculation results are compared with the ex-
periment. Based on the data obtained, according to the results of calculations,
work was carried out on a prototype, the result of which was an adjustable spot
welder. It allows you to accurately and quickly weld nickel plates to lithium
cells, creating full-fledged batteries from them, which are widely used in mod-
ern technology, including promising vehicles. The presence of sensors and a
screen allows the operator to control the charging process and the direct opera-
tion of the unit, which simplifies the use of the device.
Keywords: Capacitor energy, Spot welding apparatus, Numerical method,
Welding, Discharge time.
1 Calculation of the energy of capacitors
1.1 Formulation of the problem
An adjustable spot welding apparatus [1], developed by a team of authors, belongs to
the type of semiautomatic devices and is implemented in a capacitor method without
using a transformer [2]. The discharge for the welding process gives a block of ten
electrolytic capacitors with a voltage of 35 V and a capacity of 10,000 mF. This
method allowed to reduce the size and increase the safety of the device. The discharge
Copyright © 2020 for this paper by its authors. Use permitted under Creative Commons Li-
cense Attribution 4.0 International (CC BY 4.0).
2 S. Zuev et al.
of the capacitors in this device, and hence the release of the stored energy, occurs
almost instantaneously in the interval of 1-3 ms. This minimizes the heat-affected
zone in the welded joint. In addition, the simplicity of dosing energy and upsetting
force results in a consistently high weld quality. Main advantages the spot welding
apparatus: high performance; minimum heat affected zone due to high energy density
and short pulse; connection strength; simplicity of technology that does not require
highly qualified personnel; uniformity of the mains load at high welding currents.
Let's consider the operation of the welding device in more detail.
Features of the developed adjustable spot welding machine and its differences from
analogues:
- "Open" code of the microcontroller [3], which allows the completion and optimi-
zation of the device software.
- The cheapness of the development. According to the results of the calculations,
an
adjustable spot welder costs an average of 29% cheaper compared to analogues [4].
- Ergonomics and ease of use [5]. The device is quite easy to disassemble, and
bend the
corrugated body of the electrodes in the required direction to perform difficult-to-
access work;
- Increased maintainability due to ease of repair and availability of spare parts and
components [6].
When preparing microelectronic products for welding with an apparatus, it is nec-
essary to take into account the aspects of manufacturability. So, taking into account
the high degree of deformation during welding of trace elements, the uniformity of
which ensures the quality and reliability of the joint, it is necessary to achieve equality
and uniformity of the thickness of the welded trace elements. It is desirable to reduce
(by about 10–30%) the deformation of microelements, which is explained by the de-
sire to prevent the formation of defects in the contact and a noticeable decrease in the
cross section of the microelements being connected.
A distinctive feature of the developed device is a low rate of mass transfer in the
electrode-workpiece contact due to the short pulse duration and welding current.
During the creation of the device, the necessary parameters were calculated, such
as the resistance of the welding circuit, the discharge current with the shunt, and the
discharge current of normal operation. According to the results of these calculations,
the safe modes of operation of the device were determined [7].
An electric discharge for carrying out the welding process gives a block of ten
electrolytic capacitors with a voltage of 35 V and a capacity of 10,000 mF. Consider
the operation of the device in more detail.
After opening the transistors, the block will discharge onto a nickel plate to which
the electrodes are pressed [8]. The duration of the operating mode (discharge) is set
by the potentiometer R12 and it is 0.1; 0.2; 0.5; 1.0; 2; 5 and 10.0 milliseconds (ms).
Welding current pulses, during which heating and welding of products are carried
out, can be single and combined. To improve the quality of welding, the device has
the ability to form combined pulses, consisting of two or more parts following each
other.
Calculation of the Energy of Capacitors for a Spot Welding Apparatus by a Numerical… 3
To determine the optimal operating mode of the welding machine [9], the energy
stored in the capacitors was calculated. The main characteristics of the device depend
exactly on this value, such as, for example, welding current, max welding power [10].
Energy stored in capacitors:
E=С·U2/2=0,1·302/2=4,5·10-4 kW·ms, (1)
where C is the capacitance of the capacitor bank, f; where U — initial voltage val-
ue of transition process, V.
1.2 The sequence of calculation
The sequence of calculation can be represented as follows.
The transient process [12] of the discharge of the capacitor will be characterized by
the transition of the energy [13] of the electric field of the capacitor into the thermal
energy of the resistance of the resistor. In general, the formula will look like:
−2 t
U2 C U C2
E = I 2 Rdt = e RC dt = , (2)
0
R 0 2
where I is the discharge current of the capacitor bank, A; R — the resistance of the
discharge circuit, Ohm; t — the discharge time, s; Uс — current value of voltage on
the capacitor, decreasing exponentially with time, V.
When the resistance in the discharge circuit is equal to R = 0.015 Ohms, we deter-
mine the discharge energy in the general form:
t −2 t t −2 t t
U 2 n RC 30 2 n 0, 0150,1 n
e dt =
0 , 002 − 2 x
E= e dt = 60000 e , (3)
R 0 0,015 0 0
where tn is the discharge time interval, ms.
Draw up a general table 1 "Optimum values for setting the intervals of the dis-
charge time", calculated in accordance with the formula (3).
Table 1. Optimum values for setting discharge time intervals.
tn, ms Discharge energy (Е), 𝒌𝑾 ∙ 𝒎𝒔
0,1 5,6
0,2 10,5
0,5 21,9
1 33,14
2 41,87
5 44,94
10 44,99
Then, in accordance with formula (4), we get table 2 "The remaining percentage of
the energy of the full discharge".
4 S. Zuev et al.
E − E (t n )
= 100 % , (4)
E
where E(tn) is the discharge energy during tn, ms.
Table 2. The remaining percentage of the energy of the full discharge.
tn, ms Remaining energy percentage of the full discharge, %
0,1 87,5
0,2 76,7
0,5 51,3
1 26,3
2 6,95
5 0,13
10 0,0022
Practical use of the spot welder has shown high quality results. Figure 1 shows that
the weld spots are smooth and neat. The quantitative sample during the tests showed
the absence of lack of penetration, burnout, deep dents, cracks and splashes when
creating a spot welded joint. The lithium-ion batteries were fully functional and fully
charged. Thus, the developed apparatus can be used in the manufacture for the assem-
bly of microcircuits, if necessary, for welding miniature hinged elements to them.
For products with semi-conductive and non-conductive film coatings [11], a weld-
ing voltage pulse is formed, consisting of several unipolar welding pulses with a giv-
en shape change pattern, obtained by the energy of one quarter of the supply voltage
period. In this case, it is possible to use the mode of the apparatus, when the first im-
pulse provides an electrical breakdown of the coating, and the subsequent impulses
provide welding of products.
A number of welded materials are very sensitive to changes in the uniformity of
the electrode pressure [14]. A slight change in the geometry of the working part of the
electrode, their wear or misalignment can cause a splash of molten metal. To elimi-
nate the undesirable phenomenon, it is possible to use combined electrodes, consisting
of metal electrodes, dielectric bushings, which prevent the deviation and loss of
alignment of the electrodes. Such electrodes provide better welding of products.
The calculation results are presented in Figure 1.
2 Conclusion
The obtained calculation results, both numerical and graphic, can provide im-
portant information on the dynamics of the capacitor charge, which can be used by
other scientific groups when conducting research in related fields [15]. The conducted
review of scientific papers on the research topic showed significant interest from out-
side groups on this topic [16]. Also, the obtained data can be used to determine the
safe operating modes of this type of devices [17], to develop recommendations on the
method of thermal inspection of joints obtained by spot welding. Significant defor-
Calculation of the Energy of Capacitors for a Spot Welding Apparatus by a Numerical… 5
mations lead to a thinning of the thickness and, as a consequence, a sharp decrease in
the mechanical properties of the joint [18]. An essential prerequisite for obtaining a
good quality welded joint using the developed apparatus is a clean surface of the
products to be contacted with the same properties [19]. Welding defects can be caused
by the presence of areas of local anomalous overheating of the alloy and can be asso-
ciated with the formation of discontinuities in the process of plastic deformation [20],
which requires further research.
Fig. 1. Discharge energy of the capacitors of the spot welding apparatus. The inset shows the
welding process.
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