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High-voltage Switch is any relay protection device, the use of environmental conditions to select relay protection device to use the environment requirements, mainly refers to temperature, humidity, atmospheric pressure, coastal atmosphere (salt spray corrosion), dust pollution , chemical gases and electromagnetic interference and Other factors, taking into account the high voltage switch in many bad operating conditions, especially as an open type high voltage circuit breaker equipment running in the outdoor environment, working conditions are worse, and long years and reliable operation of the special features and key parts of the system A fully sealed product with high altitude and strong electrical resistance must be selected because only fully sealed relays have excellent long-term resistance to harsh environmental performance, good electrical contact stability, and reliable switching load capability.
1. The influence of temperature on the relay The relay is a heat-sensitive component. The high temperature can accelerate the aging of the internal plastic and insulating materials of the relay. The contacts are oxidized and the arc extinguishing is difficult. The technical parameters of the electrical components decay and the reliability is reduced. Because the high voltage switch is internally installed The flooding and thermal insulation heaters, therefore, must not be placed close to flooding and thermal insulation heaters throughout the design of the system, and should be well ventilated. Although the relay is afraid of thermal components, but too low temperature can not be ignored, low temperature can make the contact cold-stick effect is exacerbated, the contacts on the surface exposed, many manufacturers of relays that the minimum temperature of a 25 °C, but the high voltage switch application in the alpine There are also not many regions. Therefore, it is recommended that there be enough room for selection to avoid relays being unreliable due to low temperatures. Under proper conditions, heaters are added in high-cold areas to ensure reliable operation of the relays at low temperatures and to ensure stable operation of the entire system.
2. The influence of low pressure on the relay Under the condition of low pressure, the heat dissipation condition of the relay deteriorates, and the temperature of the coil increases, which changes the relay's given pull-in and release parameters and affects the normal operation of the relay. The low pressure can also insulate the relay. The resistance is reduced, the arc extinguishing of the contacts is difficult, and the contacts are easily melted, which affects the reliability of the relay. For low pressure conditions, the method of sealing the entire machine is recommended.
3. The influence of mechanical stress on relays mainly refers to the effects of vibration, shock, and impact stress elements on the anti-seismic and anti-mechanical stress of the control system. The vibration caused by the circuit breaker's self-vibration and the closing and closing operations in the high-voltage switch have more influence on the relay. Large, you should choose the middle armature relay balance mechanism, for the electromagnetic relay reed suspension structure, low natural frequency, oscillation and shock can cause resonance, resulting in relay contact pressure drop, prone to momentary disconnection or contact jitter , affect the reliability of the relay, it is recommended in the design as much as possible to use anti-vibration measures to prevent resonance.
4. Influence of insulation voltage on the relay The exposed insulator of the non-sealed or sealed relay has long-term exposure to dust, water and gas pollution, which causes its dielectric strength to decline, and it is easy to cause insulation breakdown failure. Therefore, the following points should be noted:
(1) Adequate creepage distance: General requirements are not less than 3mm;
(2) Adequate dielectric strength: There is more than AC2000V between conductors without electrical contact, and greater than AC1000V between contacts of the same group.
(3) Ability to withstand weather stress for a long time: The coil is resistant to mold and the insulation resistance level is stable and reliable for a long time.
5. The influence of the contact output (switching circuit) load mainly refers to the contact load characteristics, such as: lamp load, motor load, inductor, contactor (relay) coil, resistive load, etc.; contact load value (open circuit voltage Values, closed-circuit current magnitude, such as: low-level load, dry circuit load, low current load, large current load, etc.
Any automation equipment must really determine the nature of the load and the amount of load that are actually required. It is especially important to use suitable relay products. The failure or reliability of the relay is not reliable, mainly refers to whether the contact can complete the specified switching circuit function. If the actual load of the switch is inconsistent with the switching load specified by the selected relay, reliability will not be discussed.
Second, the use of relays should pay attention to the special problems and analysis Some engineering and technical personnel of sealed relays and non-hermetic relays believe that non-sealed products have intuitive actions and failure analysis, and the action of the fully sealed product is invisible. The subjectively identified non-sealed products are more reliable than fully sealed products. The concept of recognition is very wrong.
2. The parallel connection of relay contacts and the use of serial relay contacts in parallel cannot increase the load current, because the actions of the multiple sets of contacts of the relay are absolutely not acted simultaneously, ie, the first set of contacts that are turned on first switches the increased load. While the other contacts in parallel have not been actuated, it is easy to make the contacts damaged without contacting or welding, so that the contacts cannot be disconnected. The parallel connection of the contacts can reduce the failure rate due to the mistake of “breakâ€, but it is the opposite for the “sticky†error. The "failed" error of the contact is the main failure mode, so the parallel connection should be affirmed for improving the reliability and can be used for key parts.
3. The correct connection of relay contacts (1) In the power automation control operation, as much as possible to use moving contacts, less use of dynamic disconnect contacts, that is, when the relay contacts are connected, it should be used as much as possible to connect the movable contact . Minimize the use of dynamic disconnect contacts, because the relay of moving contacts is less than the frequency of contact bounce of relays that are moving than the contacts of moving contacts during operation. Contact jitter can cause adverse effects on the circuit and shorten the life of the contacts.
(2) The positive and negative polarity of the relay contact should be reliably connected. For relays with positive and negative polarity connections, the positive pole must be connected to the positive Q1 to the auxiliary switch SB1 and a control button K1 to the electromagnet power supply. The negative pole must be connected to the negative power supply to indicate the positive and negative polarity, otherwise the next stage design Possible connection error. Causes the relay not to act or fail.
4. The choice of relay In the three-phase alternating current motor, due to the lack of phase fault in the line, the lack of phase operation of the motor, resulting in the accident of the motor burn out, in order to solve the occurrence of such accidents, most designers chose the thermal relay with the phase loss protection. However, the reasonable selection of thermal relay must be selected according to the following requirements:
(1) For the long-term stable operation of the motor, take the heat relay relay setting current of 0.9 ~ 1.05 times or the median value is equal to the rated current of the motor, use the thermal relay setting current is adjusted to the motor rated current;
(2) Under normal circumstances, the rated current of the thermal relay should be greater than the rated current of the motor, and then select the type of the thermal relay according to the rated current. When the starting current of the motor is 6 times its rated current or the starting time exceeds 5 seconds, The setting current of the heating element is adjusted to the rated current of the motor; when the starting time of the motor is long and the impact load is dragged or the vehicle is not allowed to stop, the setting current of the heating element is adjusted to 1.1 to 1.5 times the rated current of the motor. ;
(3) The thermal relay trips due to a fault in the line or other reasons. At this time, the reset is used to reset the thermal relay. Usually the thermal relay is provided with two types of specifications: self-resetting and manual reset. In normal use, it is recommended to set it to manual reset. Make sure that the thermal relay can be reset after being treated.
1. The influence of temperature on the relay The relay is a heat-sensitive component. The high temperature can accelerate the aging of the internal plastic and insulating materials of the relay. The contacts are oxidized and the arc extinguishing is difficult. The technical parameters of the electrical components decay and the reliability is reduced. Because the high voltage switch is internally installed The flooding and thermal insulation heaters, therefore, must not be placed close to flooding and thermal insulation heaters throughout the design of the system, and should be well ventilated. Although the relay is afraid of thermal components, but too low temperature can not be ignored, low temperature can make the contact cold-stick effect is exacerbated, the contacts on the surface exposed, many manufacturers of relays that the minimum temperature of a 25 °C, but the high voltage switch application in the alpine There are also not many regions. Therefore, it is recommended that there be enough room for selection to avoid relays being unreliable due to low temperatures. Under proper conditions, heaters are added in high-cold areas to ensure reliable operation of the relays at low temperatures and to ensure stable operation of the entire system.
2. The influence of low pressure on the relay Under the condition of low pressure, the heat dissipation condition of the relay deteriorates, and the temperature of the coil increases, which changes the relay's given pull-in and release parameters and affects the normal operation of the relay. The low pressure can also insulate the relay. The resistance is reduced, the arc extinguishing of the contacts is difficult, and the contacts are easily melted, which affects the reliability of the relay. For low pressure conditions, the method of sealing the entire machine is recommended.
3. The influence of mechanical stress on relays mainly refers to the effects of vibration, shock, and impact stress elements on the anti-seismic and anti-mechanical stress of the control system. The vibration caused by the circuit breaker's self-vibration and the closing and closing operations in the high-voltage switch have more influence on the relay. Large, you should choose the middle armature relay balance mechanism, for the electromagnetic relay reed suspension structure, low natural frequency, oscillation and shock can cause resonance, resulting in relay contact pressure drop, prone to momentary disconnection or contact jitter , affect the reliability of the relay, it is recommended in the design as much as possible to use anti-vibration measures to prevent resonance.
4. Influence of insulation voltage on the relay The exposed insulator of the non-sealed or sealed relay has long-term exposure to dust, water and gas pollution, which causes its dielectric strength to decline, and it is easy to cause insulation breakdown failure. Therefore, the following points should be noted:
(1) Adequate creepage distance: General requirements are not less than 3mm;
(2) Adequate dielectric strength: There is more than AC2000V between conductors without electrical contact, and greater than AC1000V between contacts of the same group.
(3) Ability to withstand weather stress for a long time: The coil is resistant to mold and the insulation resistance level is stable and reliable for a long time.
5. The influence of the contact output (switching circuit) load mainly refers to the contact load characteristics, such as: lamp load, motor load, inductor, contactor (relay) coil, resistive load, etc.; contact load value (open circuit voltage Values, closed-circuit current magnitude, such as: low-level load, dry circuit load, low current load, large current load, etc.
Any automation equipment must really determine the nature of the load and the amount of load that are actually required. It is especially important to use suitable relay products. The failure or reliability of the relay is not reliable, mainly refers to whether the contact can complete the specified switching circuit function. If the actual load of the switch is inconsistent with the switching load specified by the selected relay, reliability will not be discussed.
Second, the use of relays should pay attention to the special problems and analysis Some engineering and technical personnel of sealed relays and non-hermetic relays believe that non-sealed products have intuitive actions and failure analysis, and the action of the fully sealed product is invisible. The subjectively identified non-sealed products are more reliable than fully sealed products. The concept of recognition is very wrong.
2. The parallel connection of relay contacts and the use of serial relay contacts in parallel cannot increase the load current, because the actions of the multiple sets of contacts of the relay are absolutely not acted simultaneously, ie, the first set of contacts that are turned on first switches the increased load. While the other contacts in parallel have not been actuated, it is easy to make the contacts damaged without contacting or welding, so that the contacts cannot be disconnected. The parallel connection of the contacts can reduce the failure rate due to the mistake of “breakâ€, but it is the opposite for the “sticky†error. The "failed" error of the contact is the main failure mode, so the parallel connection should be affirmed for improving the reliability and can be used for key parts.
3. The correct connection of relay contacts (1) In the power automation control operation, as much as possible to use moving contacts, less use of dynamic disconnect contacts, that is, when the relay contacts are connected, it should be used as much as possible to connect the movable contact . Minimize the use of dynamic disconnect contacts, because the relay of moving contacts is less than the frequency of contact bounce of relays that are moving than the contacts of moving contacts during operation. Contact jitter can cause adverse effects on the circuit and shorten the life of the contacts.
(2) The positive and negative polarity of the relay contact should be reliably connected. For relays with positive and negative polarity connections, the positive pole must be connected to the positive Q1 to the auxiliary switch SB1 and a control button K1 to the electromagnet power supply. The negative pole must be connected to the negative power supply to indicate the positive and negative polarity, otherwise the next stage design Possible connection error. Causes the relay not to act or fail.
4. The choice of relay In the three-phase alternating current motor, due to the lack of phase fault in the line, the lack of phase operation of the motor, resulting in the accident of the motor burn out, in order to solve the occurrence of such accidents, most designers chose the thermal relay with the phase loss protection. However, the reasonable selection of thermal relay must be selected according to the following requirements:
(1) For the long-term stable operation of the motor, take the heat relay relay setting current of 0.9 ~ 1.05 times or the median value is equal to the rated current of the motor, use the thermal relay setting current is adjusted to the motor rated current;
(2) Under normal circumstances, the rated current of the thermal relay should be greater than the rated current of the motor, and then select the type of the thermal relay according to the rated current. When the starting current of the motor is 6 times its rated current or the starting time exceeds 5 seconds, The setting current of the heating element is adjusted to the rated current of the motor; when the starting time of the motor is long and the impact load is dragged or the vehicle is not allowed to stop, the setting current of the heating element is adjusted to 1.1 to 1.5 times the rated current of the motor. ;
(3) The thermal relay trips due to a fault in the line or other reasons. At this time, the reset is used to reset the thermal relay. Usually the thermal relay is provided with two types of specifications: self-resetting and manual reset. In normal use, it is recommended to set it to manual reset. Make sure that the thermal relay can be reset after being treated.
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