Delixi circuit breaker mechanism spring design

The spring is a widely used component in the circuit breaker mechanism, and the critical spring has a great impact on the function of the circuit breaker. From the perspective of energy, combined with the installation space of the tension spring, the author uses the existing accounting formula of the tension spring to solve the unknown quantity from the known quantity to obtain the required tension spring parameters, and finally constitutes the planning diagram of the tension spring.

The spring circuit breaker is a widely used part in the operation organization of tension springs. Various tension springs such as cylindrical or coil springs, disc springs, leaf springs, torsion springs and so on are used in the organization, and the critical tension springs have a great impact on the function of the circuit breaker. If the opening tension spring and closing tension spring are not properly planned, the circuit breaker min, the closing will not be in place or opened.

In this paper, starting from the circuit breaker General Energy Layout, combined with the installation space of the tension spring, using the known conditions, solving the tension spring parameters, and then combining the surface treatment, strength checking, strengthening and other factors of the tension spring, the spring that meets the requirements is planned.

Delixi circuit breaker mechanism spring design

Delixi circuit breaker mechanism spring design

1. Spring planning

When planning the spring actuation organization, it is first necessary to understand the overall energy organization of the circuit breaker, that is, to confirm the energy of the contact tension spring through the additional current and additional voltage of the circuit breaker. Then according to the speed of the circuit breaker, the quality of the moving parts, the frictional resistance, etc. When the brake is opened, the energy to open the tension spring is confirmed. Finally, the energy of the closed tension spring is determined based on the closing speed, the mass of the moving parts, and the frictional force.

According to the known energy of the opening and closing tension spring, combined with the known conditions, the parameters of the tension spring are solved, and then combined with the production process and strength check of the tension spring, the tension spring that meets the requirements is planned.

1.1 Planning of opening springs

The opening spring has two main functions: one is to meet the requirements of the circuit breaker opening speed, and the other is to ensure that the circuit breaker is in place; The former needs to break the arc, and the latter needs to ensure that the dynamic and static contacts have enough opening distance after opening.

The following takes the vacuum circuit breaker as an example to plan the open spring spring, which is a cylindrical spiral tension spring. This kind of tension spring is widely used, and the tension spring does not need to be guided during operation, and the structure is simple.

Set the average opening speed vf of the vacuum circuit breaker, the opening speed vg, the opening and stopping speed ve, the insulated tie rod speed V at the end of the contact tension spring, the conductive rod mass md, the insulating tie rod mass M, the friction force Ff, the overtravel h, the energy required by the contact tension spring Ac, the energy released by the opening tension spring in the overtravel is Af1, and the energy released by the opening tension spring at the opening distance is Af2. Ac+af1+mgh-ffh = 1/2mv2, mv = (m+MD) VG, Af2 = 1/2(m+md)ve2-1/2(m+md)vg2, vf = (vg+ve)/2, so ve=2vf-vg.

Vacuum circuit breaker vf, vg have certain requirements, M, md, H are known, Ac can be obtained early, Ff can be budgeted according to the movement mode of the part, therefore, Af1, Af2 can be obtained. The energy (Af1+Af2) released by the open tension spring during the opening process is planned to be 12J. According to the output angle of the tissue, when the opening tension spring operation (i.e., from P1 + p2 = 2e/λ = 888.9n..

According to the open condition of the circuit breaker, P1≥350N, then P2≤538.9N tension spring stiffness P' = (P2-P1)/λ ≤ 7.0. In order to make the circuit breaker switch smoothly connected, it is generally required that the value of the opening tension spring P2 should not be too large, that is, the tension spring stiffness P' should be appropriately taken as a small value. P' = gd4/(8d23n), between which d - tension spring wire diameter, D2 - tension spring middle diameter, n - effective number of turns, g - tension spring shear modulus (g = 80000 - 83000 MPa). Therefore, D2 should be as large as possible.

According to the size of the space, when the tension spring is opened, the outer diameter D1 = 38 mm, the middle diameter D2 = D1-D = 31 - 35 mm (D is estimated to be 3 - 7 mm), the winding ratio C = D2/D, generally 4 - 16, and the common value is 5 - 8. If C n = 17 and D = 4.4 —— 5 mm. P1 = P0+kλ0, P0 is the initial tension of the tension spring, λ0 is the deformation of the tension spring P1.

P0 = π d3 τ 0/(8d2k), where k ≈ (4c-1)/(4c-4)+(0.615/c) = 1.21, k is the compensation coefficient of the tension spring, τ0 is the initial stress of the tension spring, and its value τ 0 = (0.1 - 0.15) τ lim is taken as τ0.

Therefore, P0 = 94n, λ 0 = (P1-P0)/k = 38.8mm. After checking, P2 < Plim (the ultimate working load of the tension spring), the tension spring satisfies the application requirements.

1.2 Planning of closing springs

It is also necessary to start with the energy of the planning of the closed tension spring. The energy of the closing tension spring is mainly allocated to the contact tension spring, the opening tension spring, the electricity that does the work when closing, the gravitational work of the moving parts, and the energy consumed by the friction of the moving parts. , during which the load energy generally accounts for 30-50% of the closing energy. Since the energy of the touch and opening tension springs has been obtained, it is possible to roughly estimate the energy of the closing tension spring.

In the case of a vacuum circuit breaker, the work done by touching the tension spring (disc spring) is mainly in the overtravel phase. According to the electrical parameters such as the additional current and breaking current of the circuit breaker, the initial pressure of the contact tension spring is P1 = 2200n, the operating pressure P2 = 3150n, the overtravel is T = 3.5mm, and the energy of the three-phase contact tension spring is E1 = 3 * (P1+P2)* T/2 = 3 *(2200+3150)* 3.5/2 = 28088n. mm≈28.1J thus, load

When the stroke of the tissue closing tension spring is S = 20 mm, then E = (P1 + P2) * S/2, P1 + P1 + P2 = 10670N. Due to the constraints of space size, it is necessary to install the tension spring in the range of the outer diameter D0 < φ 57 and the inner diameter D1 > φ 20, and it is difficult for a single tension spring to meet the above requirements. Therefore, the plan uses a combined tension spring. Fig. 2 shows a compression tension spring, and the sum of the P1 and P2 values of the combined tension spring should be satisfactory to P1 + P1 + P2 = 10670N, and each should be satisfied with P2 < Plim.

2. Planning of combined springs

When the cylindrical spiral compression tension spring is planned to accept a large load and the installation space is limited, the combined tension spring can be used. This tension spring wire has a small diameter and is easy to make. When planning a combined tension spring, the following should be noted:

1) The strength of the tension spring should be close to equal, and the following relationship should be calculated

1/D2 = D1/D2 = (Pn1/Pn2) 1/2 and PN = PN1+PN2, the ratio of Pn1 (maximum working load of external tension spring) to Pn2 (maximum working load of internal tension spring) of general combination tension spring of class g is 5:2.

2) The deformation of the tension spring should be close to equal, during which the deformation Fn of one tension spring under the maximum operating load should not be greater than the operating limit deformation Fj of the other tension spring, and the practical deformation difference can be adjusted by the gasket.

3) In order to ensure that the combined tension springs are not entangled with each other during operation, and to avoid the skew of the tension springs on the surface and inside, the rotation direction of the two tension springs should be opposite. If you choose a combination of three tension springs, you should ensure that the rotation direction of the central tension spring is opposite to the rotation direction of the outer and inner tension springs.

4) The radial clearance of the combined spring should be satisfied with the following relationship δ: δ = (d11-d22)/2 ≥ (d1-d2)/2, where d11 is the inner diameter of the outer tension spring, d22 is the outer diameter of the inner tension spring, and D1 and D2 are the wire diameters of the outer tension spring and the inner tension spring.

5) The bearing surface structure of the end of the spring should be able to avoid the deviation of the inner and outer tension springs in the operation.

3. Conclusion

Springs are widely used in circuit breaker mechanism, and critical tension springs have a great impact on the function of circuit breakers. For critical tension springs, it is necessary to ≤ 80% plim at the operating pressure P2 of the tension springs during planning to ensure that the tension springs will not be plastically deformed due to fatigue. In addition, the tension spring can be strengthened by shot peening, pressing and other methods, and its Plim can be increased by about 20%.

Of course, according to the different application occasions of the tension spring, the Plim value of the tension spring can also be increased by using appropriate materials. After galvanizing the surface of the tension spring, it is necessary to carry out dehydrogenation treatment to avoid hydrogen embrittlement of the tension spring. In short, when planning the tension spring of Delixi circuit breaker mechanism, we should not only consider the requirements of the circuit breaker mechanism, but also consider the general planning standards of the tension spring itself, so that the planned tension spring can better meet the application requirements of the circuit breaker.

Delixi circuit breaker mechanism spring design

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