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JB/T 5553-1991 Travel switch

Basic Information

Standard ID: JB/T 5553-1991

Standard Name: Travel switch

Chinese Name: 行程开关

Standard category:Machinery Industry Standard (JB)

state:Abolished

Date of Release1991-07-09

Date of Implementation:1992-07-01

Date of Expiration:2007-03-01

standard classification number

Standard Classification Number:Electrical Engineering>>Low Voltage Electrical Appliances>>K31 Low Voltage Distribution Appliances

associated standards

alternative situation:Replaced by JB/T 5553-2006

Publication information

other information

Focal point unit:Chengdu Machine Tool Electrical Equipment Research Institute

Publishing department:Chengdu Machine Tool Electrical Equipment Research Institute

Introduction to standards:

This standard specifies the type, parameters, technical requirements, test methods and inspection rules of travel switches. This standard applies to travel switches used for control, limit, positioning, travel, signal or program conversion in circuits with AC 50Hz (or 60Hz), voltage up to 380V, DC voltage up to 220V. JB/T 5553-1991 Travel switch JB/T5553-1991 Standard download decompression password: www.bzxz.net

Some standard content:

Mechanical Industry Standard of the People's Republic of China
JB5553—91
Travel switch
Published on July 9, 1991
Published by the Ministry of Machinery and Electronics Industry of the People's Republic of China
Implemented on July 1, 1992
Mechanical Industry Standard of the People's Republic of China
Travel switch
Subject content and scope of application
This standard specifies the type, parameters, technical requirements, test methods and inspection rules of travel switches. JB5553—91
This standard applies to travel switches used for control, limit, positioning, travel, signal or program conversion in circuits with AC 50Hz (or 60Hz), voltage up to 380V and DC voltage up to 220V. 2 Reference standards
GB1497
GB2423.10
GB2828
GB2900.18
GB4026
GB42J7
GB 4942.2
GB5226
Basic test methods for low-voltage electrical appliances
Basic standards for low-voltage electrical appliances
Basic environmental test procedures for electric and electronic productsBasic environmental test procedures for electric and electronic productsBasic environmental test procedures for electric and electronic productsBasic environmental test procedures for electric and electronic productsTest A:
Test B:
Test Db:
Test Fc:
Low temperature test method
High temperature test method
Alternating damp heat test method
Vibration (sinusoidal) test method
Guidelines for vibration (sinusoidal) test
Basic environmental test procedures for electric and electronic productsBatch inspectionCount sampling procedures and sampling tablesElectrical terminologyBasic terminology||tt ||Electrical terminologyLow-voltage electrical appliances
Identification and alphanumeric symbol marking of electrical terminalsGeneral rules for terminalsMethods for determining the comparative tracking index and proof tracking index of solid insulating materials under humid conditionsDegree of protection of low-voltage electrical enclosures
Glow-wire test method and guide
Fire hazard test for electrical and electronic products
General technical requirements for machine tool electrical equipment
General requirements for control circuits and electrical switching elements3 Terms, symbols and codes
3.1 Terms
3.1.1 General terms
The terms used in this standard, except for the supplementary terms, are in accordance with the corresponding terms and their definitions in standards such as GB2900.1, GB2900.18, GB1497 and JB4013.1.
3.1.2 Supplementary terms
3.1.2.1 Combined travel switch
A travel switch composed of two or more operating units installed in a protective shell at the same time. 3.1.2.2 Operating unit
The combination of a contact element in a combined travel switch and an operating system that operates it separately. 3.1.2.3 Actuator action stroke
Approved by the Ministry of Machinery and Electronics Industry on July 9, 1991 and implemented on July 1, 1992
The stroke of the actuator before the contact is closed (opened). 3.1.2.4 Release stroke
The stroke of the actuator when the contact returns to the initial position. 3.1.2.5 Full stroke of the actuator
The maximum allowable limit of the actuator stroke.
3.1.2.6 Differential stroke
The difference between the actuation stroke and the release stroke.
3.1.2.7 Contact switching time
JB555391
The time interval from the moment when the moving contact disconnects one pair of contacts to the moment when the other pair of contacts is connected. 3.1.2.8 Action position repetition error
The difference between the maximum (or minimum) value and the average value of the action stroke under the specified conditions and number of measurements. 3.1.2.9 Release force (automatic reset travel switch) After the travel switch is actuated, the force (or torque) applied to the actuator is gradually reduced to restore the contact to the initial position.
3.1.2.10 Restoring force (non-automatic reset travel switch) The force (or torque) required to restore the actuator or contact element to the initial position. 3.1.2.11 Maximum operating force
The maximum value of the force (or torque) applied to the actuator to enable the actuator to reach the full stroke position. 3.1.2.12 Snap-action contact element
Contact element whose speed of contact movement is independent of the speed of the operating system. 3.1.2.13 Driven contact element
Contact element whose speed of contact movement depends on the speed of the operating system. 3.1.2.14 Driven cross contact element
Contact element whose normally open and normally closed contacts are both in a closed state during a certain travel time when the moving contact moves from one position to another.
.3.1.2.15 Pole
Number of contact elements contained in the travel switch.
3.1.2.16 Same polarity
Double-break changeover contact with four terminals, the moving contact is shared, and the polarity of its two adjacent contacts is the same. 3.1.2.17 Reverse polarity
Double-break changeover contact with four terminals, the two moving contacts are electrically insulated from each other. 3.2 Symbols and codes
3.2.1 Symbols
This standard adopts the symbols and names of AC, DC, U., U,, l., la, CoS, Ta.95, SCPD, CTI, etc. in Article 3.1 of GB1497. 3.2.2 Codes
This standard adopts the codes and names in Article 3.2 of GB1497. 4 Product classification
4.1 Classification
4.1.1 According to the type,
a. Ordinary type;
b. Combination type.
4.1.2 According to the contact reset mode:
Automatic reset;
Non-automatic reset.
According to the purpose of the contact element:
Snap-action contact element;
Driven contact element;
Driven cross contact element.
According to the number of contact poles:
two-pole;
three-pole;
four-level.
According to the protection mode:
opening type;
protective type.
According to the type of actuator:
direct-acting plunger type;
direct-acting roller type;
roller arm type;
roller fork type;
adjustable roller arm type;
universal type;
side pressure roller type;
positive pressure roller type;
adjustable metal swing arm type;
elastic swing arm type.
Basic parameters and dimensions
Basic parameters
Rated insulation voltage (U,)
JB5553-91
The rated insulation voltage level of the travel switch is specified as: 380V; 220V; 60V. For the travel switch without clearly specified rated insulation voltage, the maximum value of the rated voltage value shall be regarded as the rated insulation voltage. 4.2.1.2 Conventional thermal current (1)
The conventional thermal current level of the travel switch is specified as: 16; 10; 5; 2.5A. 4.2.1.3
5 The selection of rated working voltage (U.) and rated working current (I,) is shown in Table 1. Table 1 Rated working voltage and rated working current Current type
4. 2. 1. 4
Rated working system
8h working system;
Rated working voltage
110;
220;
Intermittent cycle working system, the preferred values ​​of power-on duration are as follows: 15%, 25%, 40%, 60%.
4.2.1.5 Rated operating frequency
Rated working current
0.160.2,0.25,0.315,0.4;0.5,0.63;0.8,1.0,1.25;1.6,22.5,3.15,4,5,6.3;8;10;16
The rated operating frequency of the travel switch shall be selected according to Table 3 of Article 5.3.4.3 of GB1497. The specific rated operating frequency is specified by product standard 3
.
Overall dimensions and installation dimensions
JB5553--91
Overall dimensions and installation dimensions of the travel switch shall comply with product standards and product drawings approved by the prescribed procedures. 5 Technical requirements
5.1 Normal working conditions and installation conditions
5.1.1 Ambient air temperature
The upper limit of the ambient air temperature shall not exceed +40°C; the average value of the ambient air temperature for 24 hours shall not exceed +35°C; b.
The lower limit of the ambient air temperature shall not be less than -5°C. c.
Note: ①When placing an order, the user must declare to the manufacturer the working condition that the lower limit of the ambient air temperature is -10℃ or -25℃. ②For working conditions where the upper limit of the ambient air temperature exceeds +40℃ or the lower limit is below 25℃, the user should negotiate with the manufacturer. 5.1.2 Altitude
The altitude of the installation site shall not exceed 2000m. 5.1.3 Atmospheric conditions
The relative humidity of the atmosphere shall not exceed 50% when the ambient air temperature is +40℃; higher relative humidity may be achieved at lower temperatures; the average maximum relative humidity of the wettest month shall be 90%, and the average minimum temperature of the month shall be +25℃, taking into account the condensation on the surface of the product due to temperature changes.
5.1.4 Pollution level
The pollution level of the travel switch is specified as pollution level 3, unless otherwise specified in the product standard or it can only be reduced to pollution level 2 after the effective use of housing, protective coating or sealing methods (and also considering the possibility of pollutants generated by the electrical equipment during operation, the simple use of protective housing may not be effective at this time). 5.1.5 Vibration
The travel switch can work under the vibration condition of 10~55Hz frequency and 0.75mm (10g) amplitude. 5.1.6 Shell protection level
The shell protection level of the protective travel switch shall be selected according to GB4942.2. For the protective travel switch used on machine tools, it shall comply with the protection level specified in GB5226.
5.1.7 Installation category
The installation category of the travel switch is 1.
5.1.8 Installation conditions
The installation conditions of the travel switch are specified by the product standard. 5.2 Structural requirements
5.2.1 Materials
5.2.1.1 All materials of the travel switch (including metal materials, insulating materials and auxiliary materials) shall comply with the relevant standards. The grades, specifications and performance of the materials shall comply with the requirements of the drawings and relevant technical documents. 5.2.1.2 The insulating material shall be able to pass the fire hazard test. The test adopts the glow wire test method, the temperature of the glow wire tip is 960±15℃, for the insulating material of the non-current bearing parts it is 650±10℃, and the test duration is 30±1s. 5.2.1.3 The comparative tracking index of the insulating material constituting the creepage distance shall be measured, and its value shall comply with the provisions of Article 7.1.3.2 of GB1497.
5.2.2 Clearance and creepage distance
5.2.2.1 Clearance
The clearance of the travel switch shall be selected according to the values ​​listed in Table 2. 4
Rated insulation voltage
(AC effective value or DC value)
50 100
100150
150300
300≤600
JB555391
Table 2 Minimum electrical clearance
Minimum electrical clearance
Installation category
Pollution degree 2
Note: The electrical clearance values ​​specified in Table 2 are not applicable to the contact opening distance and the part affected by the arc. Special
Pollution degree 3
If the travel switch uses an electrical clearance smaller than that specified in Table 2, it must withstand the impulse withstand voltage test corresponding to the highest installation category in accordance with the provisions of Table 5 and 8.2.2.3 of GB1497. 5.2.2.2 Creepage distance
The creepage distance of the travel switch should be selected according to the values ​​in Table 3. Table 3 Minimum creepage distance
Rated insulation voltage
or working voltage
(AC effective value
or DC value)
125(127)
400(415)
Pollution degree 2
Material group
Minimum creepage distance
I,,,
Note: The minimum creepage distance specified in Table 3 does not apply to the contact opening distance and the part affected by the arc. 5.2.3 Terminals
5.2.3.1 Terminal strength
Pollution degree 3
Material group
The terminal of the travel switch should have sufficient mechanical strength, and the structure of the terminal should ensure that it is reliable and effective when connected to the specified external wire. However, it will not damage the wire and the terminal. 5.2.3.2 Capacity of connecting wires
The travel switch shall specify the type of wires (hard wire or soft wire) that can be connected to the terminal, the maximum and minimum cross-sectional areas of the wires, and the number of wires connected to the terminal at the same time.
5.2.3.3 Marking of terminal
The terminal of the travel switch shall have clear and permanent markings for easy identification, and the markings shall comply with the provisions of GB4026. 5.2.4 Protective grounding terminal
For travel switches with specific metal protective shells, a protective grounding terminal shall be set inside the protective shell. The grounding screw shall not be less than \M4 (M3.5), the grounding point must have good contact and have specific markings. The markings shall comply with the provisions of Article 7.1.7.3 of GB1497. The markings of the protective grounding terminal shall be clear and can be permanently identified. 5.2.5 Operating parameters
The operating parameters of the travel switch (such as action travel, differential, overtravel, release force, restoring force and contact opening distance, etc.) shall be specified in the product standards or drawings.
5.2.6 Other requirements
5.2.6.1 All metal parts of the travel switch must have an appropriate and reliable anti-corrosion layer, and there must be no surface or internal defects such as cracks, pores, and coating shedding. The surface of plastic parts should be smooth and flat, and there must be no cracks, pitting, bubbles, etc. The surface of the painted parts should be smooth, the paint film should be uniform, and there should be no shedding, bubbles, paint flow, etc. 5.2.6.2 Travel switches of the same model and specification should be able to ensure the interchangeability of the entire product and vulnerable parts. 5.2.6.3 The screw connection of the travel switch should be firm and no looseness is allowed. 5.3 Performance requirements
5.3.1 Operating performance
5.3.1.1 When operating the travel switch, the contacts should be able to close and open reliably, and there should be no stuck, blocked or inflexible operation. 2 The contact switching time of the quick-acting travel switch should not exceed 0.04s. 5.3.1.2
: The action position repetition error of the direct-acting travel switch should be selected according to the following values: 5.3. 1.3
0.1, 0.05, 0.03, 0.010.005mm.
5.3.1.4 The contact resistance of the travel switch should not be greater than 200mQ. 5.3.2 Temperature rise
The travel switch contacts are passed with the specified agreed heating current, and the temperature rise of its terminal does not exceed the specified value in Table 4. Table 4 Terminal overflow limit
Dielectric properties
Brass
Terminal material
Copper (or brass) tinned
Copper (or brass) tinned or nickel-plated
Other metals
Terminal temperature rise
The travel switch should be able to withstand the test voltage value shown in Table 5 and the power frequency withstand voltage test lasting 1 minute. The contact element of the travel switch, the contact distance (single break point contact distance less than 1mm, double break point contact distance less than 2×1mm) should be able to withstand the test voltage value shown in Table 6 and the power frequency withstand voltage test lasting 1 minute. Table 5 Power frequency withstand voltage test voltage value of travel switch Rated insulation voltage
60<≤300
300<≤660
Travel switch contact elements
Micro-open contact elements
Wet and heat performance
Power frequency test voltage (AC effective value)
Power frequency withstand voltage test voltage value between travel switch contact elements Rated insulation voltage
The travel switch should be able to withstand the alternating wet and heat test for 6 days under the conditions shown in Table 7. 6
Power frequency withstand voltage test (AC effective value)
2U+1000 (but not less than 1500)
3U (but not less than 500)
Cyclic change stage
High temperature and high display
Low temperature and high temperature
5.3.5 Making and breaking capacity
Temperature ℃
25→+40
JB555391wwW.bzxz.Net
Alternating damp heat test conditions
Relative humidity %
95~100
(Condensation on the surface of the test piece)
95~100
The travel switch should be able to withstand the AC and DC making and breaking capacity tests under the conditions specified in Table 8. Table 8 Switching capacity under abnormal use conditions
Note: If necessary, the number of operation cycles, operation frequency, and power-on time may be specified separately by the product standard. 5.3.6 Mechanical life
Duration h
times/min
The mechanical life of the travel switch is expressed by the number of no-load operations of the contact element. Its mechanical life times are specified in the specific product standards. The recommended mechanical life levels are as follows (expressed in 10\ times): 10, 30, 100. 300. 600. 1000. 1500, 3000. 5.3.7 Electrical life
When the AC and DC life of the limit switch is tested under the conditions listed in Table 9 at the rated operating frequency, the AC and DC life times shall be as follows:
For mechanical life of less than 10 million times, its electrical life is 20% (AC load) and 10% (DC load) of the mechanical life times; but the AC load electrical life shall not be less than 100,000 times: the DC load electrical life shall not be less than 50,000 times; b.
For mechanical life of more than 10 million times, its electrical life is 15% (AC load) and 6% (DC load) of the mechanical life times. Current type
Use category
5.3.8 Rated fuse short-circuit current
JB5553-91
Table 9 Electrical life test parameters of travel switch
or Te Shu
lef le
Unless otherwise specified in the product standard, the travel switch should be able to withstand the 1000A expected short-circuit current test. 5.3.9 Low temperature and high temperature resistance
The travel switch should be able to work normally under the conditions of low temperature -5℃ and high temperature +40℃; a.
The travel switch should have the ability to adapt to transportation and storage in the environment of low temperature -25℃ and high temperature +55℃. 5.4 Acceptance and maintenance
The user has the right to conduct quality acceptance of the travel switch according to the requirements of this standard. cosp2
Under the condition that the user complies with the storage, installation and use rules, the manufacturer shall be responsible for repair, replacement and refund if the product is damaged or cannot work normally due to poor manufacturing quality within 12 months from the date of installation of the travel switch, but not more than 18 months after the manufacturer delivers it to the user.
6 Test methods
Except for the supplementary provisions of this standard, the test methods of the travel switch shall be carried out in accordance with the relevant provisions of GB998. 6.1 General test conditions
6.1.1 Test requirements
The travel switch shall be manufactured according to the drawings and technical documents approved by the prescribed procedures, and each test or each complete sequence test shall be carried out on a new a.
, clean product;
b. The travel switch shall be tested according to the parameters (or methods) specified in the standard. However, for the convenience of testing, the tested travel switch shall be considered equally effective if it adopts more stringent parameters (or methods) than those specified in the standard. C.
The test shall be installed according to the provisions of this standard. Before the test, the tested travel switch shall be operated several times with no load or load (less than the rated load).
6.1.2 Test values ​​and their tolerances
The test values ​​of the travel switch shall comply with the provisions of the standard. The allowable deviations of the main test values ​​are shown in Table 10. Table 10 Allowable deviations of the main test values
Test value name
Allowable deviation
Test value name
Power factor
Time constant
The deviations of the test values ​​have been specified in this standard and the test shall be carried out according to the provisions of this standard. Permissible deviation
If the standard only specifies the test value but not the permissible deviation of these values, the test shall be carried out under conditions slightly more severe than the specified value.
6.2 Verification structure requirements
6.2.1 Fire hazard test of insulating materials
JB5553-91
The fire hazard test of insulating materials shall be carried out in accordance with GB5169.4. 6.2.2 Determination of comparative tracking index (CTI) of insulating materials The test equipment, preparation of electrolyte, test procedures and methods for the determination of comparative tracking index (CTI) of insulating materials shall comply with the relevant provisions of GB4207.
6.2.3 Determination of electrical clearance and creepage distance The determination of electrical clearance and creepage distance shall be measured using conventional measuring tools with a reading accuracy higher than 0.05mm, and the calculation and measurement methods shall comply with the relevant provisions in Appendix A of GB1497.
6.2.4 Test of strength of wire terminals
The test shall be carried out with the wire with the maximum allowable load surface and the minimum allowable cross-section. The wire shall be connected and removed 5 times each. The tightening torque applied to the terminal shall be tested according to the tightening torque specified in Table 24 of GB1497. This test shall be carried out on two tested terminals respectively. After each test, the wire pressing screws on the terminal shall be loosened and the wire shall be removed. The second test shall be carried out with a new wire. After the test, the terminal shall not be permanently deformed and shall be able to work normally. 6.2.5 Test of enclosure protection level
The test method of the enclosure protection level of the travel switch shall be carried out in accordance with GB4942.2. 6.2.6 Vibration test
The vibration test shall be carried out in accordance with the requirements of GB2423.10 and GB2424.7. During the test, the travel switch shall not be allowed to have poor contact or disconnection.
6.2.7 Test of operating parameters
The operating parameters shall be measured using special equipment. 6.3 Verification performance requirements
6.3.1 Operating performance test
When operating the travel switch by hand, there shall be no stuck, blocked or inflexible movement. The closing and opening of the contacts shall be monitored by a signal lamp with a voltage not exceeding 6V. 6.3.2 Contact switching time test
The contact switching time test shall be carried out on special equipment. The movement of the control pin of the special equipment shall be between 10 and 30 mm/min. Repeat the measurement 5 times to obtain a total of 10 data (action and return), and the maximum value shall not exceed 0.04S. 6.3.3 Action position repetitive error test
The test shall be carried out on a special operating machine. The movement of the control pin of the operating machine shall enable the push rod of the contact element to produce a speed of 10 to 30 mm/min. The operating machine shall be equipped with a measuring instrument that meets the accuracy requirements. In the readings of the travel switch measured 10 times, the difference between the maximum value (or minimum value) and the average value shall not exceed the specified value. 6.3.4 Contact resistance test
When measuring contact resistance, a DC voltage of 6V and a current of 1A should be applied to the contact, and the voltage drop method should be used to measure continuously for 3 times. The maximum value of the 3 measured data should not exceed 200m. When measuring the contact resistance of the normally open contact, the actuator of the travel switch should be placed at a position about one-third of the overtravel. The order of each contact resistance measurement is: the contact element under test is in the closed state → connect the current → measure the voltage drop → pass the current in the opposite direction → measure the voltage drop → cut off the current → disconnect the contact under test. The arithmetic average of the measured forward contact resistance and reverse contact resistance is taken as the primary contact resistance value.
6.3.5 Temperature rise test
6.3.5.1When the travel switch is subjected to the temperature rise test, all contacts in the closed state should be connected, and the agreed heating current should be applied, and the test should be carried out at the same time. The temperature is measured by the thermocouple method. 6.3.5.2 After the test, the temperature rise of the terminal should not exceed the value specified in Table 4 of this standard. The temperature rise of the conductive parts shall not cause any damage to the adjacent parts and shall not hinder the operation of the travel switch. 6.3.6 Dielectric performance test 6.3.6.1 Test voltage application location: JB5553-91 8. a. Between the live parts of the contact element and the parts designated to be grounded; b. Between the two ends of the disconnected contacts of the contact element; between the live parts of adjacent contact elements. c. 6.3.6.2 During the test, the voltage waveform is a sine wave with a frequency between 45 and 62 Hz. When the high voltage is short-circuited, the current should not be less than 0.5 A. The test time is 1 min. During the factory test and sampling test, the test time can be 1 s. During the test, the leakage current should not exceed 50 mA, and there is no breakdown or flashover.
6.3.7 Wet and hot performance test
6.3.7.1 Before the test begins, the travel switch should be placed under the test conditions for at least 8 hours as a pretreatment to prevent unnecessary surface condensation caused by sudden changes in the environment.
The test should be measured in the last 1 to 2 hours of the "low temperature and high humidity" stage. At this time, the temperature in the test box is 25 ± 3 ° C, the humidity should be controlled at 95% to 98%, and condensation should be avoided on the surface of the test product. The insulation resistance is measured first, and then the power frequency withstand voltage test is carried out. The specific requirements are shown in GB2423.4.
6.3.7.2 After the wet and hot test, the travel switch can still meet the following requirements: the insulation resistance of the travel switch should not be less than 1.5MO; a.
The travel switch can still pass 80% of the power frequency withstand voltage test; b.
The operating performance of the travel switch should meet the requirements of Article 5.3.1.1. c
6.3.8 Switching capacity test
6.3.8.1 The breaking capacity test shall be connected according to the circuits shown in Figures 6 to 9 of GB1497. The circuit parameters, number of operation cycles, operation frequency and power-on time shall comply with the provisions of Table 8. Both the normally open and normally closed contacts shall be tested for breaking capacity, but it is allowed to be performed on two products separately.
Figure 6 of GB1497 is applicable to the breaking capacity test of adjacent contacts that are not electrically separated in the use category of AC-11 and DC-11. Figure 7 of GB1497 is applicable to the breaking capacity test of adjacent contacts that are not electrically separated in the use category of AC-14, AC-15, DC-13 and DC-14.
Figure 8 of GB1497 is applicable to the breaking capacity test of adjacent contacts that are electrically separated in the use category of AC-11 and DC-11. Figure 9 of GB1497 is applicable to the breaking capacity test of adjacent contacts that are electrically separated in the use category of AC-14, AC-15, DC-13 and DC-14.
The results of the switching capacity test shall meet the following requirements: 6.3.8.2
During the test, no electrical fault, mechanical fault, contact welding, arcing to the shell, etc. shall occur; a.
The pre-ignition time of the AC switching capacity test shall not be greater than 0.15; the arc time of the DC switching capacity test shall not be greater than 0.15b.
It can still pass the power frequency withstand voltage test;
d. After more than 2 times of no-load closing and opening, it shall be able to meet the requirements of Article 5.3.1.1. 6.3.9 Mechanical life test
6.3.9.1 The mechanical life test shall comply with the following conditions: 8. During the mechanical life test, the test product shall not be maintained, repaired or replaced with parts. The wear of the contacts shall not be considered as mechanical wear, but if the contact bridge is deformed or broken for a long time, it must be considered as a mechanical failure; b. When conducting a mechanical life test, the operating frequency shall comply with the product standard. However, in order to shorten the test cycle, the test operation frequency can be increased without affecting the mechanical performance; c. The overtravel of the travel switch actuator should be adjusted to 50%-80% of the original design value of the overtravel of the actuator; the connection between the operating machine and the actuator of the travel switch should have enough free range of motion to avoid the operating machine hindering the free movement of the actuator d.
;
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