The solution (contact break) is the distance between the working surfaces of the contacts in their off position.
Failure (lapping) is the distance traveled by the moving contact from the moment the contacts come into contact with the auxiliary surfaces until they are completely closed by the working surfaces. Produced with a lapping spring.
The initial contact pressure (pressure) is generated by the lapping spring. Depending on the type of device, it is in the range of 3.5 - 9 kg.
The final contact pressure (pressure) is created by an electro-pneumatic or electromagnetic drive, depending on the type of apparatus, it must be less than 14 - 27 kg.
Figure 4. Template for measuring contact break
a) contactors of the PK MK 310 (MK 010) MK 015 (MK 009) type and group switches, b) cam switches and breaking contacts of the MKP 23 contactor
The contact line of the contacts must be at least 80% of the total contact area.
The contact gap is determined by the smallest distance between the contacts in the open position. It is measured by an angular template, graduated in millimeters (Figure 4 a and b).
The failure of contacts in each of the devices is measured depending on the design of the contact system. So the measurement of the failure of contacts in contactors of the PC type and contactor elements of group switches is carried out with the device turned on with angular templates of 12 and 14 degrees.The angle of deviation of the holder of the moving contact from the stop of the contact lever (Fig. mm
The failure of the contacts of the cam elements at cam switches is determined in the closed position of the contacts by distance but(Figure 5, b). Distance " but » 7-10 mm corresponds to a dip of 10-14 mm
Figure 5. Determination of contact failure.
a) determination of the failure of contacts of contactors of the PC type and contactor elements of group switches b) - determination of the failure of contacts of cam elements to cam devices
The initial contact pressure is determined by the compression force of the lapping spring. The final pressing of the contacts is measured with a dynamometer with closed contacts, the counting of which is carried out at the moment when it will be possible to pull out a strip of paper clamped between the contacts with a compressed air pressure in the electro-pneumatic drive of 5 kg / cm 2. With an electromagnetic drive, the closing coil voltage must be 50V. In this case, the dynamometer must be fixed to the movable contact so that the force applied to it crosses the contact line of the contacts and coincides with the direction of movement of the contact at the moment of separation.
For knife disconnectors, the quality of the contact is checked by the force on the handle when turned on, it should be at least 2.1-2.5 kg / cm 2, and when turned off - 1.3-1.6 kg / cm 2.
The line of contact of the contacts must be at least 80% for all devices, except for the devices specified in the technical conditions. Determined by the print on copy paper when the machine is turned on
Solution of contacts of electronic devices
In low voltage electronic devices, the contact solution is mainly determined by the arc extinguishing criteria and only at significant voltages (above 500 V) does its value begin to depend on the voltage between the contacts. Experiments show that the arc leaves the contacts already at a solution of 1 - 2 mm.
More unfavorable conditions for extinguishing the arc are obtained with a constant current, the dynamic forces of the arc are so significant that the arc moves intensively and extinguishes already at a solution of 2 - 5 mm.
According to these experiments, it can be considered that in the presence of a magnetic field for extinguishing the arc at a voltage of up to 500 V, it is possible to take a solution value of 10 - 12 mm for a constant current, for an alternating current, 6 - 7 mm is taken for all current values. An excessive increase in the solution is not necessary, because it leads to an increase in the stroke of the contact parts of the apparatus, and, consequently, to an increase in the dimensions of the apparatus.
The presence of a bridge contact with 2 breaks makes it possible to reduce the contact stroke, while maintaining the total value of the solution. In this case, a solution of 4 - 5 mm is usually taken for each break. Particularly excellent arc extinguishing results are obtained with an AC bridge contact. Excessive solution reduction (less than 4 - 5 mm) is usually not done, because errors in the manufacture of individual parts can significantly affect the size of the solution. As the need to obtain small mixtures, it is necessary to anticipate the possibility of its adjustment, which complicates the design.
If the contacts work in the criteria when they can be heavily contaminated, the solution must be increased.
Usually the solution increases and. for contacts that open a circuit with high inductance, because at the moment of extinction of the arc, significant overvoltages occur and with a small gap there may be a reignition of the arc. The solution also increases for the contacts of protective devices in order to increase their reliability.
The solution grows significantly with an increase in the frequency of the alternating current, because the rate of voltage rise after the arc is extinguished is very high, the distance between the contacts does not have time to deionize and the arc ignites again.
The magnitude of the solution on an alternating current of the highest frequency is usually determined experimentally and is very dependent on the design of the contacts and the arc chute. At voltages of 500-1000 V, the size of the solution is usually taken as 16-25 mm. Huge values apply to contacts that turn off circuits with higher inductance and huge currents.
The contacts wear out during operation. In order to ensure their reliable contact for a long time, the kinematics of the electronic device is made in such a way that the contacts touch earlier than the movable system (the system for moving the movable contacts) reaches the stop. The contact is attached to the moving system via a spring. Due to this, after contact with the fixed contact, the movable contact stops, and the movable system moves forward until it stops, further compressing the contact spring.
Thus, if the fixed contact is removed with the closed position of the movable system, then the movable contact will shift to a certain distance, called a dip. Failure determines the margin for contact wear at a given number of operations. With other equal criteria, a larger dip provides a higher wear resistance, i.e. longer service life. But a bigger failure usually requires a stronger drive system.
Contact push- the force compressing the contacts in the place of their contact. Distinguish between the initial pressing at the moment of the initial contact of the contacts, when the dip is equal to zero, and the final pressing with the complete failure of the contacts. As the contacts wear out, the dip is miniaturized, and, as it follows, the additional compression of the spring. The final press is closer to the original. So Makar, initial pressure is one of the main characteristics in which the contact must remain functional.
The main function of the failure is to compensate for the wear of the contacts, therefore the magnitude of the failure is determined first by the value of the greatest wear of the contacts, which is usually taken: for copper contacts - for each contact up to half of its thickness (total wear is the total thickness of the 1st contact); for contacts with solders - Until the soldering is completely worn out (complete wear is the total thickness of the soldering of the movable and fixed contacts).
In the case of a contact grinding process, especially rolling, the magnitude of the dip is very often significantly greater than the maximum wear and is determined by the kinematics of the moving contact, which provides the required rolling and slippage. In these cases, in order to reduce the total travel of the movable contact, the axis of rotation of the movable contact holder can be positioned closer to the contact surface.
The values of the little permissible contact pressure are determined from the criterion for maintaining a measured contact resistance. If special measures are taken to maintain a measured contact resistance, the values of small contact pressure can be reduced. So, in special compact equipment, the contact material of which does not give an oxide film and the contacts are completely firmly protected from dust, dirt, water and other external influences, contact pressure is miniaturized.
The final contact pressure does not play a decisive role in the operation of contacts, and its value at the theoretical level should be equal to the initial pressure. But the choice of failure is almost always associated with the compression of the contact spring and an increase in its force, therefore it is constructive to obtain uniform contact presses - initial and final - is unrealistic. Usually, the final contact pressure with new contacts exceeds the initial one by one and a half to two times.
Dimensions of contacts of electronic devices
Their thickness and width are very much dependent on both the design of the contact connection and the design of the arcing device and the design of the entire apparatus as a whole. These dimensions in different designs can be very different and very much depend on the purpose of the device.
It should be seen that the size of the contacts, which often break the circuit under current and extinguish the arc, is better to increase. Under the influence of the often broken arc, the contacts become very hot; an increase in their size, mainly due to the heat capacity, makes it possible to lower this heating, which leads to a very noticeable decrease in wear and to an improvement in the criterion for extinguishing the arc. Such an increase in the heat capacity of contacts can be carried out not only due to a direct increase in their size, but also due to arc-extinguishing horns associated with contacts in such a way that not only an electronic connection is made, but also a good heat removal from the contacts is ensured.
Contact vibration- the phenomenon of repeated rebound and subsequent closure of contacts under the influence of various circumstances. Vibration can be damped when the amplitudes of the rebounds decrease and after some time it stops, and non-damped when the vibration phenomenon can last any time.
The vibration of the contacts is very harmful, because a current passes through the contacts and at the moment of rebounds between the contacts an arc arises, causing increased wear, and from time to time, welding of the contacts.
The prerequisite for the damped vibration resulting from the switching on of the contacts is the impact of the contact against the contact and their next rebound from each other due to the elasticity of the contact material - mechanical vibration.
It is unrealistic to remove one hundred percent mechanical vibration, but it is always better that both the amplitude of the first rebound and the total vibration time are smaller.
The vibration time is characterized by the ratio of the contact mass to the initial contact pressure. It is better to have this value smaller in all cases. It can be reduced by lowering the mass of the movable contact and increasing the initial contact pressure; but the decrease in mass should not affect the heating of the contacts.
Especially huge values of the vibration time at switch-on are obtained if, at the moment of touching, the contact pressure does not increase abruptly to its own real value. This happens when the design and kinematic diagram of the movable contact is incorrect, when, after touching the contacts, the initial pressure is established only after the selection of backlash in the hinges.
It is worth noting that an increase in the grinding process usually increases the vibration time, because the contact surfaces, when moving relative to each other, encounter bulges and roughnesses that contribute to the rebound of the movable contact. This means that the amount of lapping should be selected in good dimensions, usually determined empirically.
Electrodynamic forces are a prerequisite for continuous vibration of contacts that appears when they are closed. Because vibration under the action of electrodynamic forces occurs at huge current values, the resulting arc is very intense and due to such vibration of the contacts, usually they are welded. Thus, this type of contact vibration is completely unacceptable.
To reduce the ability to generate vibration under the action of electrodynamic forces, current leads to the contacts are often made in such a way that the electrodynamic forces acting on the moving contact compensate for the electrodynamic forces arising at the contact points.
When a current of such magnitude passes through the contacts, at which the temperature of the contact points achieves the melting temperature of the contact material, adhesion forces arise between them and the contacts are welded. Such contacts are considered welded when the force that ensures their divergence cannot overcome the adhesion forces of the welded contacts.
A more common means of preventing contact welding is the use of suitable materials, and it is also advisable to increase the contact pressure.
A solution of contacts of electrical devices
In low voltage electrical devices, the contact solution is mainly determined and only at significant voltages (over 500 V) does its value begin to depend on the voltage between the contacts. Experiments show that the arc leaves the contacts already at a solution of 1 - 2 mm.
The most unfavorable conditions for extinguishing the arc are obtained with a constant current, the dynamic forces of the arc are so great that the arc actively moves and extinguishes already at a solution of 2 - 5 mm.
According to these experiments, it can be considered that in the presence of a magnetic field for extinguishing the arc at a voltage of up to 500 V, it is possible to take a solution value of 10 - 12 mm for direct current, for alternating current, 6 - 7 mm is taken for any current values. An excessive increase in the solution is undesirable, since it leads to an increase in the stroke of the contact parts of the apparatus, and, consequently, to an increase in the dimensions of the apparatus.
The presence of a bridge contact with two breaks makes it possible to reduce the contact stroke, while maintaining the total value of the solution. In this case, a solution of 4 - 5 mm is usually taken for each break. Particularly good results for arc extinguishing are obtained with the use of an AC bridge contact. Excessive reduction of the solution (less than 4 - 5 mm) is usually not done, since errors in the manufacture of individual parts can significantly affect the size of the solution. If it is necessary to obtain small solutions, it is necessary to provide for the possibility of its adjustment, which complicates the design.
If the contacts work under conditions where they can be heavily contaminated, the solution must be increased.
Usually the solution increases and. for contacts that open the circuit with, since at the moment of extinction of the arc, significant overvoltages appear and with a small gap, re-ignition of the arc is possible. The solution is also increased for the contacts of protective devices in order to increase their reliability.
The solution significantly increases with an increase in the frequency of the alternating current, since the rate of voltage rise after the arc is extinguished is very high, the distance between the contacts does not have time to deionize and the arc ignites again.
The magnitude of the solution on alternating current of high frequency is usually determined experimentally and strongly depends on the design of the contacts and the arc chute. At voltages of 500-1000 V, the size of the solution is usually taken as 16-25 mm. Larger values refer to contacts that switch off circuits with higher inductance and higher currents.
Failure of contacts of electrical devices
The contacts wear out during operation. To ensure their reliable contact for a long time, the kinematics of the electrical apparatus is performed in such a way that the contacts touch before the movable system (moving system of movable contacts) reaches the stop. The contact is attached to the moving system via a spring. Due to this, after contact with the stationary contact, the movable contact stops, and the movable system moves forward until it stops, additionally compressing the contact spring.
Thus, if the fixed contact is removed in the closed position of the movable system, then the movable contact will be displaced by a certain distance, called a dip. The dip determines the margin for contact wear at a given number of operations. All other things being equal, a larger dip provides a higher wear resistance, i.e. longer service life. But a larger failure usually requires a more powerful drive system.
Contact push- the force compressing the contacts in the place of their contact. A distinction is made between the initial pressing at the moment of the initial contact of the contacts, when the dip is equal to zero, and the final pressing with the complete failure of the contacts. With the wear of the contacts, the dip decreases, and, consequently, the additional compression of the spring. The final press is closer to the initial one. In this way, the initial push is one of the main parameters at which the contact must remain functional.
The main function of the failure is to compensate for contact wear., therefore, the magnitude of the failure is determined primarily by the value of the maximum wear of contacts, which is usually taken: for - for each contact up to half of its thickness (total wear is the total thickness of one contact); for contacts with solders - Until the soldering is completely worn out (complete wear is the total thickness of the soldering of the movable and fixed contacts).
In the case of a contact grinding process, especially rolling, the magnitude of the dip is very often much greater than the maximum wear and is determined by the kinematics of the movable contact, which provides the required amount of rolling and slipping. In these cases, to reduce the total stroke of the movable contact, it is advisable to place the axis of rotation of the holder of the movable contact as close to the contact surface as possible.
The values of the minimum permissible contact pressure are determined from the conditions for maintaining a stable contact resistance. If special measures are taken to save, the values of the minimum contact pressure can be reduced. So, in special small-sized equipment, the contact material of which does not give an oxide film and the contacts are absolutely reliably protected from dust, dirt, moisture and other external influences, contact pressure is reduced.
The final contact pressure does not play a decisive role in the operation of contacts, and its value should theoretically be equal to the initial pressure. However, the choice of failure is almost always associated with the compression of the contact spring and an increase in its force; therefore, it is structurally impossible to obtain the same contact pressure - initial and final -. Typically, the final contact pressure for new contacts exceeds the initial one and a half to two times.
Dimensions of contacts of electrical devices
Their thickness and width very much depend both on the design of the contact connection and on the design of the arcing device and the design of the entire apparatus as a whole. These dimensions in various designs can be very diverse and strongly depend on the purpose of the apparatus.
It should be noted that the size of the contacts, which often break the circuit under current and extinguish the arc, is desirable to increase. Under the action of a frequently broken arc, the contacts become very hot; an increase in their size, mainly due to the heat capacity, makes it possible to reduce this heating, which leads to a very noticeable decrease in wear and to an improvement in the conditions for extinguishing the arc. Such an increase in the heat capacity of the contacts can be carried out not only by directly increasing their dimensions, but also by means of arc-extinguishing horns connected to the contacts in such a way that not only the electrical connection is carried out, but also a good heat removal from the contacts is ensured.
Vibration of contacts of electrical devices
Contact vibration- the phenomenon of periodic rebound and subsequent closure of contacts under the influence of various reasons. Vibration can be damped when the amplitudes of the rebounds decrease and after a while it stops, and non-damped when the vibration phenomenon can last any time.
Vibration of contacts is extremely harmful, since current passes through the contacts and at the moment of rebounds between the contacts an arc appears, causing increased wear and sometimes welding of the contacts.
The cause of the damped vibration that is obtained when the contacts are turned on is the impact of the contact against the contact and their subsequent rebound from each other due to the elasticity of the contact material - mechanical vibration.
It is impossible to completely eliminate mechanical vibration, but it is always desirable that both the amplitude of the first rebound and the total vibration time are as small as possible.
The vibration time is characterized by the ratio of the contact mass to the initial contact pressure. It is desirable to have the smallest value in all cases. It can be reduced by reducing the mass of the movable contact and increasing the initial contact pressure; however, the decrease in mass should not affect the heating of the contacts.
Particularly long vibration times at switch-on are obtained if, at the moment of touching, the contact pressure does not abruptly increase to its actual value. This happens when the design and kinematic diagram of the movable contact is incorrect, when, after touching the contacts, the initial pressing is established only after the selection of backlash in the hinges.
It should be noted that an increase in the grinding process, as a rule, increases the vibration time, since the contact surfaces, when moving relative to each other, encounter irregularities and roughness that contribute to the rebound of the movable contact. This means that the amount of lapping should be selected in the optimal size, usually determined empirically.
The reason for the persistent vibration of the contacts, which appears when they are closed, are. Since vibration under the action of electrodynamic forces appears at high current values, the resulting arc is very intense and due to such vibration of the contacts, as a rule, they are welded. Thus, this kind of contact vibration is completely unacceptable.
To reduce the possibility of vibration under the action of electrodynamic forces, current leads to the contacts are often made in such a way that the electrodynamic forces acting on the moving contact compensate for the electrodynamic forces arising at the contact points.
When a current of such magnitude passes through the contacts, at which the temperature of the contact points reaches the melting temperature of the contact material, adhesion forces appear between them and the contacts are welded. Such contacts are considered welded when the force that ensures their divergence cannot overcome the adhesion forces of the welded contacts.
The simplest means of preventing contact welding is to use appropriate materials and to increase the contact pressure appropriately.
It is customary to call a contact failure the distance by which the point of contact of the moving contact with the fixed contact can be displaced from the position of complete closure if the fixed contact is removed. Since it is practically difficult to determine the size of the wire, it is limited to checking the gap formed between the plate on which the fixed contact is fixed and the contact holder bracket when the contacts are closed.
Initial pressure is the force created by the contact spring at the point of initial contact of the contacts. If the initial pressure is insufficient, the contacts may weld, and if the required initial pressure is exceeded, the clarity of the contactor operation is disturbed. Initial press test is performed as follows.
The line of contact of the contacts is preliminarily marked on the moving contact. When changing the initial push, the contacts must be in the open state.
A strip of tissue paper is clamped between the movable contact and the plate on which the movable contact is installed. A dynamometer hook is threaded into the opening of the movable contact, which is pulled until the paper can be freely moved by pulling it out by hand. The dynamometer readings at this moment give the value of the initial depression.
The final push is the force generated by the contact spring.
The check of the final pressing is carried out with the contactor fully switched on, similar to the measurement, only the paper in this case is laid between the movable and fixed contact.
Adjustment of the amount of pressing the contacts is made by changing the position of the bracket of the holders of the moving contacts by tightening or loosening the nuts.
Operating principle:
The contactor works as follows. When voltage is applied to the target of the coil, the core attracts the armature, which presses the moving contacts against the fixed ones. The core rests on shock-absorbing springs, which soften the impact of the armature on the core when the contactor is switched on. By means of a spring, the armature returns to the off position. The path of movement of the armature rotating on the axis is limited by the stop. When the armature is attracted to the core, the movable contacts are pressed against the fixed contacts and close the auxiliary contacts, which bypass the "Start" button so that after the motor starts it can be released.
Operating principle of the Switching device:
To prevent vibrations of the contacts, the contact spring creates a pre-pressure equal to half of the final contact force. Vibration is greatly influenced by the rigidity of the fixed contact attachment and the vibration resistance of the entire contact as a whole. In this respect, the design of the KPV-600 series is very successful. the fixed contact is rigidly attached to the bracket. One end of the arc quenching coil is attached to the same bracket. The second end of the coil, together with the lead, is securely fastened to an insulating plastic base. The latter is attached to a sturdy steel bracket, which is the base of the apparatus. The movable contact is made in the form of a thick plate. The lower end of the plate has the ability to rotate about the pivot point. Thanks to this, the plate can roll over the crack of the stationary contact. The output is connected to the moving contact using a flexible conductor (connection). Contact pressure is generated by a spring.
When the contacts are worn, the cracker is replaced with a new one, and the movable contact plate rotates 180 ° and its undamaged side is used in work.
To reduce the melting of the main contacts by the arc at currents of more than 50 A, the contactor has arcing contacts - horns. Under the action of the magnetic field of the arc-extinguishing device, the reference points of the arc quickly move to the bracket connected to the stationary contact and to the protective horn of the movable contact. The armature is returned to its initial position by a spring.
The main parameter of the contact is the rated current, which determines the dimensions of the contactor.
The KPV series of contacts has a design with an NC main contact. Closing is performed due to the action of a spring, and opening is due to the force developed by an electromagnet.
The rated current of the contactor is the current of intermittent-continuous operation. In this mode, the contactor is on for no more than 8 hours. After this interval, the device must be turned on and off several times (to clean the contacts from copper oxide). After that, the device turns on again.
KTPV-500 type, has a direct current electromagnet, movable contacts are isolated from the case, which makes it safer to service the device.
The movable contact with the spring is attached to an insulating arm connected to the contactor shaft. Due to the easier extinguishing of the AC arc, the contact gap can be taken small. Reducing the solution makes it possible to approach the axis of rotation. The small distance of the point of contact of the contacts from the axis of rotation makes it possible to reduce the force of the electromagnet required to turn on the contact, which makes it possible to reduce the size and power consumption of the magnet.
The movable contact and the armature of the electromagnet are interconnected through the contactor shaft. Unlike DC contactors, the movable contact in the KPV-600 contactor does not have rolling. The device is disconnected under the action of the contact springs and the forces of the weight of the moving parts.
The principle of operation of the arc extinguishing device.
In DC contactors, devices with electromagnetic blowing are most widely used. When the magnetic field interacts with the arc, an electrodynamic force arises that moves the arc at high speed. To improve the cooling of the arc, it is driven into a slot made of an arc-resistant material with high thermal conductivity.
When the contacts diverge, an arc arises between them. The arc can be considered as a conductor with current. The coil creates a c.f., under the action of which a current is generated. This flow passes through the coil core, pole pieces and the air gap in which the arc is burning.
To ensure the conditions for extinguishing the arc, it is necessary to raise the current-voltage characteristic of the arc with increasing current.
In the region of low currents, with increasing current, the contact solution required for quenching increases. At a given speed of their movement, more time is required to reach the required solution. In the region of high currents, the quenching process is determined by electrodynamic forces. The higher the rate of extension of the arc by dynamic forces, the less time it takes for the arc to reach its critical length.
In high-frequency installations, in order to ensure normal operating conditions for generators, cos φ circuits tend to be closer to unity.
For reliable and fast extinguishing of the arc in the area of low currents, low current contactors with replaceable magnetic blast coils are used. These coils have a rated current of 1.5 - 40 A. At a low cut-off current, a coil is installed with a large number of turns, due to which the necessary magnetic field is created to extinguish the arc in a short time.
ELECTROSPETS
ELECTROSPETS
AC contactors, contact adjustment.
The main parameters of the contact device are the contact gap, contact failure, and pressing on the contacts of the contactors, therefore they are subject to mandatory periodic checking and adjustment in accordance with the data in Table. one.
|
Contactor type |
Contact solution, mm |
The gap controlling the dip, mm |
Initial push. kg (N) |
End pressure kg (N) |
|
Table 1... Contactors of the KT6000, KT7000 and KTP6000 series |
||||
|
|
||||
|
KT6012, KT6022, |
2,2-2,4 |
2,5-2,9 |
||
|
KT5013, KT6023, |
1,5-1,6 |
1,8-2,2 |
||
|
KT6014, KT6024, KT7014, KT7024 |
1,1-1,2 |
1,4-1,7 |
||
|
KT7015, KT7025 |
0,85-0,95 |
1.1-1,4 |
||
|
KT6032, KTP6032, KT6033, KTP6033 |
2,0-2,2 |
3,7-4,5 |
||
|
1,4-1,56 |
3-3,4 |
|||
|
1.1-1,2 |
2,6-3 |
|||
|
5,3-5,5 |
7,32-8,43 |
|||
|
13,1-16,6 |
||||
|
7,32-8,43 |
||||
|
13,1-16,6 |
||||
|
4-4,2 |
6,12-7,13 |
|||
|
3,2-3,3 |
5,34-5,23 |
|||
Continuation of table 1.
|
Contactor type |
Contact solution, mm |
The gap controlling the dip, mm |
Initial pressing, kg (N) |
Final pressure, kg (N) |
|
KT6052, KTP6052. KT6053, KTP6053 |
10 - 12,5 |
3,7 - 4 |
9,6-10,0 |
18
-
21 |
|
KT6054 |
6,5-6,8 |
12,5-15 |
||
|
KT6055 |
4,8-5 |
10,5-13 |
||
| Contactors series KT6000 / 2 | ||||
|
KT6022 / 2 |
7,5-8,5 |
1,7-2 |
2.2,-2,4 |
2,5-2,9 |
|
KT6023 / 2 |
1,5-1,6 |
1,8-2,2 |
||
|
KT6032 / 2, KT6033 / 2 |
3,3-3,5 |
2,0-2,2 |
3,7-4,5 |
|
|
KT6042 / 2, KT6052 / 2, KT6043 / 2, KT6053 / 2 |
10-12,5 |
3,7-4 |
9,6-10,0 |
18-21 |
Fig. 2... Positions (on, off) of contacts for adjusting solutions, dips, pressing and simultaneous contact of contacts of contactors of the KT6000, KTP6000, KT7000 and KT6000 / 2 series. a - contactors KT6032 / 2, KT6033 / 2; b, c - contactors of the KT6000, KTP6000, KT7000 series; 1 - the place of laying the paper tape when measuring the initial pressing on the contact; 2 - gap controlling contact failure; 3 - contact line; 4 - the place of laying the paper tape when measuring the final pressure on the contact; 5 - contact solution; 6 - direction of application of force when measuring the final pressure on the contacts; 7-directional application of force when measuring the initial pressure on the contacts; 8 - adjustment of pressing on the contact; 9 - adjustment of the failure and simultaneity of touching Contacts.
Checking for failures of contacts. Since it is practically impossible to measure the magnitude of the dip, check the gap that controls the dip, that is, the gap formed when the main contacts are fully closed, between the contact holder and the adjusting screws of the lever carrying the movable contact (Fig. 2). The failure of the main contacts in the closed position of the magnetic system of the contactor is monitored. With the full value of the contact dip, a full final pressure on the contact is ensured. As the contacts wear, the dip decreases, therefore, the final pressing on the contact decreases, which can lead to overheating of the contact. It is not allowed that the size of the gap controlling the failure be less than 1/2 of its original value indicated in table. one.In contactors of the KT6000 / 2 series, the failure of the main contacts is established by rotating one adjusting screw in contactors for currents of 160 A or two adjusting screws in contactors for currents of 250, 400 and 630 A. The design of the contact system of contactors of the KT6000, KTP6000 and KT7000 series allows double restoration of the failure, which is carried out by rotating the adjusting screw (in contactors for 100 and 160 A), the sleeve (in contactors for 400 A) and adjusting screws (in contactors for 250 and 630 A).
The size of the gap controlling the dip is measured with a feeler gauge. It is desirable that the magnitude of the contact failures be the greatest. Having established the required gap and making sure that there is no skewing of the movable contact, the adjusting screws must be locked, and the bushings must be fixed with the plate petals.
Checking the simultaneity of touching contacts. Non-simultaneous contact of the main contacts is checked with a probe that controls the gap between the contacts when the other contacts touch each other. It is convenient to control the simultaneity of touching the contacts using a 3-6 V light bulb connected in series to the contact circuit, but within the limits specified in table. 1. Non-simultaneous contact of new contacts is allowed up to 0.3 mm. It should be borne in mind that the more precisely the dips are adjusted, the less the non-simultaneous contact of the contacts.
Checking contact solutions. Contact solutions are checked with a gauge and must correspond to the dimensions indicated in table. 1. If the solution is not normal, then by turning the eccentric bar "the armature time around the axis, they are brought back to normal (contactors of the KT6000 / 2 series). In contactors of the KT6000, KTP6000, KT7000 series (except for KTP6050), the contact opening is adjusted by turning the stop around the axis by 90 °. In these contactors, several stop positions are provided, which determine the steps for adjusting the solution.
Checking the pressing of contacts. The pressing of the main contacts is determined by the elasticity of the contact springs. The pressing of the contacts is adjusted according to the highest values indicated in the table. 1, so that after wear of the contacts, it does not fall below the permissible values. The degree of wear of the contacts (crackers) is determined by the magnitude of the dip. If, as a result of the wear of the crackers, the failure is less than the minimum values indicated in table. 1, the contacts should be replaced with new ones. When measuring pressure, it is necessary to ensure that the tension line is approximately perpendicular to the contact plane of the contacts.
Initial push is the force created by the contact spring at the point of initial contact of the contacts. Insufficient initial pressing leads to melting or welding of contacts, and increased initial pressing can lead to fuzzy switching on of the contactor or it getting stuck in intermediate positions.
Initial hit test produced with open contacts (no current in the coil). In practice, the control of the initial pressing of the contacts is carried out not on the line of contact of the contacts, but between the moving contact and the lever using a dynamometer, a strip of thin paper and a loop (for example, from steel wire or keeper tape). The loop is applied to the moving contact, and a thin paper tape is inserted between the shaft protrusion and the adjusting screw - for 100 and 160 A contactors (Fig. 2, c), between the holder and the adjusting sleeve - for 400 A contactors (Fig. 2, b ), between the holder and two adjusting screws - for contactors for 250, 400 and 630 A (Fig. 2, a). Then, the tension of the dynamometer determines the force at which the strip of paper is easily pulled out. This force should correspond to the initial contact pressure indicated in table. 1. In fig. 2, the arrow indicates the direction of tension of the dynamometer. If the tension does not correspond to the table, it is necessary to change the tightening of the contact spring by turning the adjusting screws, nuts and bushings. After setting the required pressure, the adjusting devices must be rigidly fixed so that the setting is not disturbed.
Final push. The final push characterizes the contact pressure when the contactor is on. Correspondence of end clicks to tabular ones is possible only for new contacts. As the contacts wear, the amount of final pressure will decrease. To measure the final pressure, it is necessary to completely turn on the contacts, for which the armature of the magnetic system is pressed against the core and wedges, or the retraction coil is connected to full voltage. A strip of burning paper is clamped between the contacts. The loop is put on the movable contact (as when measuring the initial tension). The loop is pulled back by the hook of the dynamometer until the contacts disperse so much that the paper can be moved. The dynamometer readings in this case give the value of the final pressing on the contacts. The end press is not adjustable, but controlled. If the final pressing does not correspond to that indicated in the table. 1, it is necessary to replace the contact spring and carry out the entire adjustment process from the beginning.