In recent years, with the deepening of the socialist market economy, product competition has become increasingly fierce. Some electrical manufacturers, in order to promote and promote their products, arbitrarily specify technical performance parameters that do not conform to scientific and standard standards in their samples or product manuals, which causes confusion. The reason for this is that there is a lack of genuine understanding of the meanings of those parameters; The second is that the meaning of the parameters is clear, but in order to make users feel that their product is superior to others, intentionally blurring the concept and elevating it, regardless of which situation, it is not serious and irresponsible. To clarify the issue, we will express the meaning of electrical parameters according to current national and international standards, in order to clarify the source. The definition of "rated working voltage" in the "Electrotechnical Terminology for Low Voltage Electrical Appliances" (GB/T2900.18-92) is "the working voltage value that ensures the normal operation of electrical appliances under specified conditions." The rated working voltage in China and more than 30 countries around the world is AC 50Hz 220/380V, while in more than 10 countries such as the UK and Australia it is AC 50Hz 240/415V, and in countries such as Bangladesh, India, Malaysia, Pakistan, Singapore, etc. it is AC 50Hz 230/400V. This time, there are also 127/220V and so on. IEC Publication 38 suggests that in the future, countries should adopt a standardized voltage of 230/400V (with phase voltage as the numerator and line voltage as the denominator) due to the wide variety of voltage types that affect trade and communication. However, this reform involves a wide range of aspects and is a vast engineering system. Therefore, countries around the world still use the original voltage system.
Since it is 220/380V in our country, it is impossible to have a working voltage of 400V. However, in many manufacturers' short-circuit breaker samples, their short-circuit breaking capacity column clearly indicates a rated voltage of 400V. With the same short-circuit breaking current, users may think that it is higher than 380V (if only from the numbers, 400V is naturally much higher than 380V). If this behavior of raising the working voltage is not intentional confusion, it is a misunderstanding in understanding. When conducting short-circuit breaking tests and overload operation performance tests on circuit breakers, it is stipulated that the test voltage is 1.05Ue, which is understood by some as 1.05X380=400V. In fact, the 1.05 times Ue here is the power frequency recovery voltage (steady-state recovery voltage). According to GB/T14048.1, the tolerance of voltage Ue for test parameters is+5%, which means that the fluctuation of grid voltage can be within the range of 0-5%, which is 380-400V. The power frequency recovery voltage is 1.05 times Ue, which includes this fluctuation range (the maximum is the upper limit value). Another misconception is that the general transformer to the user has a low voltage ratio of 10/0.4KV, which means that the primary voltage of the transformer is 10KV, while the secondary voltage (to the user) is 0.4KV, which is 400V. Therefore, the rated voltage of its circuit breaker product is set at 400V. This is a fallacy. The 400V on the secondary side is the no-load voltage of the transformer. When calculating the load voltage, the voltage drop inside the secondary winding should be considered, which is about 5% of the voltage value. Therefore, the actual load voltage of 0.4 is 380V. For transformers (or generators), the rated voltage can be represented by the no-load voltage, while the rated voltage of electrical equipment (including switchgear) can only be understood correctly and the actual performance assessment can only be the load voltage. The standard voltage settings and rated electrical voltages for three-phase four wire systems or AC systems in GB156-93 are specified as 220V, 380V, 660V, etc. The standard also specifies the rated voltage of generators, which are 230V, 400V, 690V. The standard also stipulates that "the rated voltage of the electrical equipment matched with the generator output terminal can be the rated voltage of the generator, as specified in the product standard." However, it seems that there is currently no circuit breaker in China that can be matched with the generator (or transformer) output terminal.
In summary, the statement that the rated voltage of a product is either 400V or 690V is incorrect. The definition of rated insulation voltage in GB/T1900.18 is: "The standard voltage value used to measure the insulation strength, electrical clearance, and creepage distance of different potential parts of an electrical appliance and its components under specified conditions. Unless otherwise specified, the ratio is the maximum rated working voltage of the electrical appliance." The equivalent use of IEC 947-1 (first edition in 1998) in GB/T14048.1 "General Principles for Low Voltage Switchgear and Control Equipment" emphasizes the insulation coordination of the system. Therefore, the condition for electrical appliances to be used in power systems is that the rated insulation voltage of the electrical appliance should be higher than or equal to the rated voltage of the power system. According to standard regulations, if an electrical product has multiple operating voltage values, such as 380V (the voltage level of most products) and 660V (commonly used in mines), its rated insulation voltage can be set at 660V. After calibrating the rated insulation voltage, the minimum creepage distance of the product is determined based on the pollution level applicable to the product (usually level 3 for circuit breakers) and the CTI value of its insulation components (compared to the leakage trace index) (this CTI value determines the group of insulation materials, divided into I, II, IIIa, IIIb). For example, with a rated insulation voltage of 660V, pollution level 3, material groups IIIa and IIIb, the minimum creepage distance of an electrical appliance that can withstand long-term voltage is 10mm. Electrical products can design the creepage distance of their insulation components based on this value, without the need to arbitrarily increase their rated insulation voltage.
Nowadays, some circuit breaker manufacturers, in order to improve their competitiveness, claim that their rated insulation voltage is 800V, which is one level higher than others' 660V, and their circuit breaker rating is the highest, which is 660V, so there is no need to raise it. And there are two points that cannot be ignored. Firstly, as the rated insulation voltage increases, the creepage distance needs to be increased. If the pollution level and the group of insulation materials remain unchanged, the minimum creepage distance should be 12.5mm when Ui (rated insulation voltage) is 800V, which is 2.5mm more than when Ui=660V; Secondly, according to the product standards of circuit breakers, after conducting overload operation performance tests and short-circuit breaking capacity tests, withstand voltage (power frequency withstand voltage) verification is required. The applied voltage is twice the rated insulation voltage. For Ui=660V, the withstand voltage is 1320V, and for Ui=800V, the withstand voltage value needs to be increased to 1600V, which actually increases the burden. But the most important thing is to regularly test the power frequency surface voltage value. When Ui=660V, the withstand voltage value is 2500V for 1 minute. When Ui=800V, the withstand voltage value is 3000V. Therefore, that meaningless display, to be honest, is to add trouble to oneself. According to GB/T14048.1, "For electrical appliances intended for use in places where serious consequences must be taken seriously due to insulation faults (such as installation category VI or for use in large capacity power supply systems or requiring isolation functions), a voltage level higher than the rated insulation voltage should be used for creepage distance. It is recommended to increase the rated insulation voltage by two or more voltage levels in the R10 priority coefficient." The R10 priority coefficient is 1.25. The first voltage above 660V is 800V, and the second voltage is 1000V. According to the above regulations, 1000V should be selected, with the same pollution level and material group as 660V. Its creepage distance should not be less than 16mm. However, due to the non selective protection (no three-stage protection) of the molded case circuit breaker, and their rated current generally below 800A, they are not suitable for installation category IV (power level) and large capacity power supply systems. It can be seen that choosing Ui greater than 660V is not practical, but only increases waste and trouble.
3. Regarding the working current of the auxiliary contact as a microswitch for the auxiliary contact (or auxiliary switch), it has two current parameters: the agreed heating current and the working current. There are multiple working currents, but the agreed heating power source is only one. The definition of the agreed heating power supply current in GB/T2900.18 is: "The maximum current that a switching device can carry when the temperature rise of each component does not exceed the limit value under the 8-hour working system under specified conditions." Its working current is determined by the load function of the electromagnet it controls in the closed state. Therefore, the agreed heating current and working current are two different concepts. In Appendix C of GN14048.5-93 "Part 1: Electromechanical Control Circuit Electrical Appliances and Switching Components for Low Voltage Switchgear and Control Equipment", "Examples of nominal rated values of auxiliary contacts for certain usage categories", the operating currents of AC-15 and DC-13, which are currently widely used, are listed. In AC-15 category, when the auxiliary contact has Ith=2.5A, the power (capacity) of the control electromagnet in the closed state is 180VA; Ith=5A, control power is 360VA, Ith=10A, control power is 720VA; DC-13 (DC) Ith=1A, control power is 28W, Ith=2.5A, control power is 69W, Ith=5A, control power is 138W, Ith=10A, control power is 275W. Based on the load power of the controlled electromagnet and the voltage value of the micro switch (auxiliary contact), its working current can be calculated. For example, if Ith=3A, the control power of Ith=2.5A can be referred to. When it is AC-15, the control power is 180VA (in accordance with the regulations of AC-15 for controlling AC electromagnet loads greater than 72VA), 180VA/380V=0.47A, 180VA/220V=0.81A, which is the operating current of the auxiliary contact at 380V and 220V voltages; For example, DC-13 (control DC electromagnet), Ith=2.5A, control the capacity (power) of the electromagnet to be 69W, 69W/220V=0.31A, 69W/110V=0.63A, which is the working current of the auxiliary contact at 220V and 110V. It is important to determine the working current of the auxiliary contact because the electrical operation performance experiments of the auxiliary contact, as well as the abnormal making and breaking capacity experiments, are all related to the value of Io. The value of Io, whether it is large or small, does not meet the requirements of the product.
Upon reviewing the 1997 revised industry standards for a certain type of molded case circuit breaker and two other types of universal circuit breakers, which still account for a considerable proportion of the domestic market, it was found that the regulations for the rated working current of auxiliary contacts are very confusing and do not comply with the national standards. If a certain circuit breaker specifies Ith as 1A, 3A, and 6A respectively. At AC380V, the operating currents are 0.3A, 0.4A, and 3A (all of which belong to AC-15 category), and the power of the controlled AC electromagnet in the closed state is calculated to be 114VA, 152VA, and 1140VA, respectively; At DC220V, with Ies of 0.15A, 0.15A, and 0.2A, the power of the DC electromagnet is 33W, 33W, and 66W, respectively. Obviously, it does not comply with the provisions of GB14048.5 standard. The other two universal circuit breakers are regulated to have an AC solenoid power of 300VA and a DC solenoid power of 60W. This is based on the old standards AC-11 and DC-11, but AC-11 and DC-11 were ordered to be cancelled as early as 1993, so it is unreasonable to apply them again. The above three questions may not be entirely correct, and we hope to receive guidance from experts.
The relevant standards and their explanations should be used as follows:
GB/T3367.9-1984 Railway Locomotive Terminology - Traction Electrical Equipment Terminology
28.31 Interlocking contact
"Electrical contacts used to prevent certain electrical components from operating under certain conditions."
GB/T10-1984 Railway Locomotive Terminology - Traction Electrical Equipment Names
10.3.12 Auxiliary contact
10.3.13 Interlocking contact "
GB/T2900.18-1992 Electrotechnical Terminology - Low Voltage Electrical Appliances
5.3.1 Contact system
An electrical component consisting of moving contacts, stationary contacts, and related conductive components, as well as all structural components such as elastic components, fasteners, and insulation components.
5.4.6 Interlocking mechanism
A mechanical interlocking mechanism designed between several switching devices or components to ensure that the switching devices or their components operate in the prescribed order or to prevent misoperation.
5.3.1.8 Auxiliary contacts
A contact connected to the auxiliary circuit of a switching device and operated mechanically by the switching device
GB/T2900.36-1996 Electrotechnical Terminology - Electric Traction
25.13 Interlock circuit
A circuit that connects mechanical, electrical, or other devices, such as through auxiliary contacts, to make the working status of one device depend on the working status and position of another or several devices.
30.31 Interlocking contact
An electrical contact used to prevent an electrical appliance from operating under certain conditions
Based on the above standards, it can be seen that except for GB/T3367.10, where interlocking contacts and auxiliary contacts are both used as entries, the other standards choose one of the two as an entry, indicating that the two express the same thing, but the features emphasized by the two are different. The auxiliary contact emphasizes its difference from the main contact, and in the two standards that do not include the auxiliary contact as an entry, the word "auxiliary contact" is used in other entries to emphasize its difference from the main contact. The interlocking contact emphasizes its function. Auxiliary interlocking does not appear as an entry in these standards. It is recommended to use "interlocking contacts" to represent individual electrical interlocking contacts and auxiliary contacts with electrical interlocking functions. "Interlocking contact system" refers to the system related to interlocking contacts as the main term, and "auxiliary contacts" should be used when emphasizing differentiation from main contacts. Do not use "auxiliary interlocking" when it is not necessary.
5. Voltage resistance, power frequency withstand voltage, withstand voltage, insulation dielectric strength, and power frequency withstand voltage
These terms appear in professional books, technical documents, regulations, and other textual materials, all of which refer to the effective value of the power frequency sine voltage that does not cause breakdown under specified test conditions.
The regulations regarding national and industry standards are as follows:
GB/T2900.25-1994 Electrotechnical Terminology - Rotating Electrical Machines
6.2.50 High voltage test, Dielectric test
The test of applying high voltage to insulation to determine whether the strength of the insulation medium meets the requirements
GB/T755-1987 Basic Technical Conditions for Rotating Electrical Machines
6.2 Ground insulation withstand voltage test.
TB/T2436-1993 General Technical Conditions for Rotating Electrical Machines for Railway Locomotives and EMUs
7.2 Insulation dielectric strength of the motor
The motor winding should be able to withstand a 1-minute insulation withstand voltage test on the base and between the windings
TB/T1333-1996 Basic Technical Conditions for Locomotive Electrical Appliances
5.12.3 Power frequency withstand voltage
The electrical appliance should be able to withstand a power frequency test voltage (effective value) for 1 minute without breakdown or flashover
GB/T1333-1996 Basic Technical Conditions for Locomotive Electrical Appliances
5.12.3 Power frequency withstand voltage
The electrical appliance should be able to withstand a power frequency test voltage (effective value) for 1 minute without breakdown or flashover
GB/T2900.18-1992 Electrotechnical Terminology - Low Voltage Electrical Appliances
6.1.67 Power frequency withstand voltage
The effective value of the power frequency sinusoidal voltage that does not cause breakdown under specified test conditions
GB/T163185-1996 Basic Test Methods for Rotating Traction Motors
17 Voltage withstand test
The motor shall undergo a withstand voltage test at the specified test voltage value under hot conditions for 1 minute, and the insulation shall not be broken down. The frequency of the test voltage is 50Hz, and the waveform is an actual sine wave
GB/T2900.15-1997 Electrotechnical Terminology - Transformers, Transformers, Transformers, Voltage Regulators, Reactors
2.1.48 Rated insulation level
The insulation of transformer type electrical equipment is designed to withstand a set of test voltages under specified conditions.
Note: These test voltages are:
a) Rated lightning impulse and rated short-circuit withstand voltage at power frequency
b) Rated lightning impulse and rated operating impulse withstand voltage.
Among the words mentioned in the title, "pressure resistance" is a non-standard term, which is basically not used in written language. The rest can be found in the standard. Most of these standards were introduced in previous years to align with international standards, which means they were directly translated. Due to the different English vocabulary used by different countries or organizations, there are also people who translate the same English into different Chinese. However, it is inappropriate to use different terms to represent the same thing in our textual materials, as this is not conducive to technical communication and concise and clear textual expression. There are two types of voltage endurance: power frequency and impulse, and the term specifically refers to the imprecise power frequency voltage endurance. Power frequency withstand voltage has the possibility of withstanding air pressure. The insulation dielectric strength is the purpose of the voltage withstand test and is not intuitive enough. There is a suspicion of duplication between "withstand" and "receive" in the power frequency withstand voltage. It is recommended to uniformly use the power frequency withstand voltage to represent the withstand voltage test of applying a 50Hz sine wave to the insulation, with an effective value higher than the normal working value for 1 minute without flashover breakdown, to determine whether the insulation dielectric strength meets the requirements.
The reason for the non-standard use of famous terminology is due to lagging standards and weak standardization awareness. With the development of socialist market economy and the integration of the world economy, the standardization of terminology will become more important and urgent.