First, the water resistance cabinet principle Water resistance starter cabinet is a widely used motor starting equipment in recent years. Water resistance, that is, liquid resistance (adding electrolytic powder in water to make water resistance), as the name implies, is to connect a liquid resistance in the motor stator circuit (squirrel-cage motor) or rotor circuit (winding motor), and the motor is in the process of starting. The resistance of the liquid-state resistor is automatically reduced steplessly in a predetermined time until the resistance value approaches zero, the liquid resistance is automatically cut off, and the motor is put into normal operation. It can start up to 2-3 times per hour.
Second, the movement process water resistance cabinet operation process: the high voltage switch cabinet closing, the water resistance cabinet receives the high voltage switch cabinet closing signal, the water resistance cabinet movement plate starts to run from top to bottom, within the set time The resistance value of the moving plate gradually decreases. When the resistance is close to zero, a vacuum switch in the water blocking cabinet is sucked by a limit switch, the water resistance is shorted, the motor is started, and the delay is delayed. After a few seconds, the movable plate automatically resets to the original state and waits for the next start. If the water blocking cabinet is not completed within a predetermined time, it will send out a fault alarm signal and automatically cut off the switch cabinet to ensure that the motor is not open.
Third, the shortcomings of the water resistance cabinet Water resistance is inefficient, only soft start. If it is used as a speed control, the water resistance cabinet box (liquid resistance part) must be electrified for a long period of time. Once the tank leakage or the liquid resistance is reduced or dry, a production accident or safety accident will occur. And due to the long-term electrification of the liquid resistance of the tank and the serious heat generation, peripheral cooling equipment is required to maintain operation. Therefore, the relative human maintenance costs will also increase.
Fourth, the transformation of water resistance tanks in the actual transformation of the site: Although the water tank resistance exists in the above shortcomings, but customers in the transformation of the water tank resistance will still retain the frequency of water resistance start mode.
(1) There are two types of water resistance cabinets in general. According to the different types of motors, two types of water resistance are connected in series: 1. The water resistance of the rotor string means that the motor is a wound-type motor, that is, the rotor circuit is not short-circuited. At this time, the soft start is gradually realized by changing the resistance value of the rotor circuit in the starting process.
2. The stator string water resistance means that the motor belongs to a squirrel-cage motor, ie the rotor circuit has been short-circuited inside the motor. At this time, soft start is gradually realized by changing the resistance value of the stator circuit in the starting process.
(B) According to the implementation of different ways, divided into two kinds of water resistance 1, the size of the temperature change resistance that is in the start-up process, due to the liquid electrolyte within the liquid temperature increases, the electrolyte molecules activity increased, so that the resistance The value gradually decreases, and the terminal voltage is gradually changed to achieve the purpose of soft start.
2. Increase the plate lift motor in the cabinet. Increase the plate lift motor through the cabinet, change the distance between the input and output plates at a uniform speed, change the size of the resistance value, and gradually change the voltage of the machine terminal to achieve the purpose of soft start.
Note: If the temperature changes the resistance value, it mainly belongs to the stator series water resistance series (ie the squirrel-cage motor).
If the resistance value is changed by the plate lifting motor, the stator and rotor series water resistance can be achieved. At present, the commonly used method is through the pole plate lifting and lowering method to facilitate the control of the start-up process.
Fifth, the internal structure of the water resistance (A) If the resistance is changed by temperature, the interior of the cabinet mainly includes:
1. The bypass cabinet is mainly short-circuited after the startup is completed.
According to the principle of different, and the number of short-circuit contactors, and some water resistance completely dragged after short-circuited, and some short-circuited, the water resistance is still charged.
According to customer needs, choose vacuum circuit breaker or vacuum contactor. The vacuum circuit breaker needs to be divided and closed, and the vacuum contactor is divided into the electrical hold and the mechanical hold type. The electrical hold does not need to add an additional shutoff operation, and the power down is the break, while the mechanical hold needs the shutoff operation.
2. The main body of the water resistance cabinet includes three independent water tanks. Each tank has a fixed copper plate at the bottom. The upper part of the water tank has a fixed copper plate, which leads to a single line. (For squirrel-cage motors: stator water resistance)
According to the size of the motor, the required volume of heat-dissipating liquid is calculated, and the volume of the cabinet body is large or small. For example, if the motor is 10 MW, the body of the water resistance cabinet may reach 10m*2m*4m.
(II) The plate lifts and changes the resistance. The inside of the cabinet mainly includes: a water tank (three-phase separation), a set of plates, a plate lifting motor and the corresponding bearings, and short-circuit contactors (short-circuit contactors are also required by customers Need), PLC, etc.
Sixth, the operation mode (the actual operation of the site based on the data and implementation methods)
(1) Temperature change resistance value 1. After the manufacturer's debugging in the power frequency mode, each plate is immersed in water, and the electrolytic powder according to the calculation is added to the water. At start-up, after power-on, the water temperature rises gradually, the electrolyte activity increases, the resistance between the plates gradually decreases, and the voltage at the motor end gradually decreases from low to high. According to the adjustment time, after the start Short contact vacuum contactor (temperature change resistance is mainly used for squirrel-cage motor), start is completed, water resistance is thrown off. Because of the water resistance of this principle, when the motor is restarted continuously, the start-up characteristics will be different due to inconsistent water temperatures at each restart. In the case of a long startup interval, the start-up characteristics can be basically consistent.
2. After the high voltage in frequency conversion mode, directly short the contactor (shorted contactor action signal is taken from the normally open point of high voltage switch QF0).
(B) Plate lift to change the resistance (focus on the introduction)
1. After the exercise process is finished, the plates are immersed in water and the electrolytic powder based on the calculation is added to the water. Before starting, the upper plate is at the top, and when starting, the upper plate is gradually moved down by the lifting motor. (Some settings are down a few seconds, stop for a few seconds, continue down, repeat). As the distance between them decreases, the resistance between the corresponding two plates decreases, and the voltage at the motor terminal gradually goes from low to high. When the upper plate moves to the lowest limit, the vacuum contactor is short-circuited. At the same time, the upper plate began to rise upwards, and when it reached the maximum limit, the start was completed. In this type of water resistance, when the motor is started continuously, the difference in starting characteristics will not be large, but the servo motor and other components will increase the maintenance work of the water resistance cabinet. (For squirrel-cage and wire-wound motors).
2. Actual data and control logic referenced at the site (1) When the general water resistance is activated, the starting current multiple is between 2 and 3.5 times, and the pressure drop at the grid side can meet the capacity requirement of the upper transformer;
(2) According to the motor size, the starting time is generally set to 20 ~ 40 seconds, the time is generally adjustable, generally more than 40 seconds, the switch cabinet will have anti-time limit protection;
(3) "Water resistance start signal". The general water resistance tanks are now controlled by PLC. The water tank start signal is taken from the corresponding “switch breaker state†of the switch cabinet, that is, the breaker of the customer's switch cabinet. After closing, the PLC of the water resistance cabinet receives the signal, and it starts to start, for example, the plate begins to move downward;
(4) After the breaker of the switch cabinet is opened, the PLC of the water resistance cabinet receives the signal, and the shorted contactor is broken;
(5) That is, the condition of the water resistance switch contactor action is the closing of the high voltage circuit breaker QF0 (taken from the QF0 normally open point).
3. Modifications to be made at the scene after the water resistance cabinet is rebuilt by the inverter (1) Water resistance of the rotor string (Corresponding winding motor, manual bypass)
1 The transformation of the primary circuit is the same as the ordinary frequency conversion transformation;
2 The transformation of the secondary circuit shall lead to a pair of “short-circuit contactor normally closed point†from the short-circuit contactor of the water resistance cabinet and be connected to the “emergency stop†circuit of the inverter. It can be understood as: if the water resistance is short If the contactor is not shorted, the inverter cannot start. It should be noted that the "remote/local" transfer switch must be bypassed when accessing the "emergency stop" circuit. That is, after the rotor of the winding motor is shorted, it is started as a squirrel-cage motor;
3 Water resistance cabinet start conditions are stringed into the power frequency state.
4 field application case introduction. Anhui Huaining Shangfeng Cement adopts the frequency conversion transformation of “rotor string water resistance†mode. The on-site motor parameters are shown in the following table:
The site requires water resistance cabinet transformation frequency conversion, and in the frequency mode of operation to retain the water resistance function of the water resistance cabinet, the motor is a three-phase asynchronous winding motor, water resistance cabinet type is increased in the cabinet plate lift motor (that is, plate lift Change resistance). Inverter is a bracket and a manual bypass cabinet. Once the inverter bypass cabinet has the same wiring as the standard wiring, as shown in Figure 1, the 10KV line coming from the customer bus will not pass through the water resistance cabinet (only the customer's AC380V control power to water resistance cabinet).
At this time, in the inverter mode, the short-circuit contactor in the bypass cabinet of the water-resistance cabinet is equivalent to the short-circuit rotor here, so that the winding-type motor is changed into a squirrel-cage motor for use by the frequency converter. In the power frequency mode, after the motor is softened and the soft rise is successful, the short circuit breaker in the bypass cabinet of the water resistance cabinet is equivalent to a shorted rotor here, so that the winding motor is changed into a squirrel cage motor for labor. Frequency use.
When the power frequency mode is used, the QS3 is firstly closed, and the DCS is remotely closed to close the QF circuit breaker. After the water resistance cabinet receives the QF closing signal and the power frequency status, the water resistance cabinet is operated. At this time, the water resistance cabinet plate comes from above. Under running, through the water resistance cabinet to achieve a soft start, when the plate is running to the bottom, there is a limit switch, through the chain, water supply switch cabinet contactor KM a signal, so that the vacuum contactor KM pull in the water resistance cabinet The water resistance is shorted out and maintained, and the winding type becomes the start of the squirrel-cage motor. After a delay of several seconds, the movable plate is automatically reset to its original state, waiting for a next start.
When operating in variable frequency mode, the QS1 and QS2 isolation switches are closed first, DCS starts QF closing, and high-voltage power enters the inverter. (The water resistance cabinet startup signal is serially connected to the power frequency state and cannot be started at this time), while KM water After the switch contactor receives the QF closing signal, the KM directly short-circuits and turns the wire into a squirrel-cage motor. After receiving the KM short-circuit signal, the inverter remotely starts/stops/adjusts the variable-frequency output through the DSC.
In addition, I have also seen an alternative rotor series water resistance and frequency conversion transformation. The user directly opens the rotor connection of the motor and short-circuits the copper directly on the rotor to become a squirrel-cage motor. At this point, the water resistance has been completely thrown off. However, if the inverter fails and the inverter is turned to the industrial frequency, the copper on the rotor needs to be removed (it can't be removed without softening, which is equivalent to the direct power frequency startup of the squirrel-cage motor, leading to the customer's transformer capacity. I can't stand it. It's too much trouble. However, the right of choice rests with the user. The user thinks that the rotor of his/her own will often cause a shotgun phenomenon, so it is appropriate to short-circuit it.
(2) Stator string water resistance (for squirrel-cage motors, manual bypass)
This kind of transformation is relatively complex. The main contents to be determined are as follows:
1 Short circuit breaker. There are at least one short-circuit contactor, and sometimes two or three. For example, it is necessary to inquire about the sequence of closing and opening of the contactors. This must be clarified in the automatic bypass cabinet because it is automatically changed. In the frequency conversion process, it may cause serious consequences. It is necessary to ask whether the self-locking mode of each contactor is electrically maintained or mechanically maintained. In the case of electrical hold, the same signal can be used for opening and closing. If it is maintained mechanically, the opening and closing should be designed separately.
2 Water block start signal. Before the frequency conversion reformation, the water resistance cabinet start signal receives the “circuit breaker normally open point signal†(which is the normally open signal of the busbar high voltage switch cabinet QF0, that is, when the QF0 is closed, normally open becomes normally closed, and the water resistance cabinet starts. If the frequency is softened, if the frequency conversion is modified, it is generally required to increase the inverter's "power frequency status" signal in the circuit that starts the water resistance cabinet start signal. That is, when the power frequency, the water resistance is still normal start, if the frequency conversion, the water resistance cabinet does not move.
3 water resistance shorted signal. Before the frequency conversion reformation, the short circuit signal received by the water resistance cabinet is the “polar plate lower limit position travel switch signalâ€. After the frequency conversion is reformed, it can be changed flexibly according to the requirements. It is necessary to increase the control signal to increase the opening and closing circuit in the closing and opening circuit of the short-circuit contactor. The control method is determined according to customer requirements and system security.
4 field application case introduction. Zaozhuang Quantou Cement Plant adopts the frequency conversion reformation of “stator string water resistance†mode. The on-site motor parameters are shown in the following table:
The schematic diagram of a wiring diagram is shown in Fig. 2. The short contactor in the water resistance cabinet is KM, and the high pressure passes through the water resistance cabinet.
This system is the stator string water resistance, the water resistance cabinet has only one contactor KM, the contactor is the mechanical retention type, the secondary principle change of the system has the following parts.
The first part is that the PLC program changes the logic and leads the line to the KM's split and close coils. The water resistance switch contactor KM control scheme is as follows:
In the power frequency mode, the KM is still controlled by the logic of the water resistance cabinet to achieve soft start.
In the variable frequency mode, when the high-voltage starter circuit breaker QF is closed, the KM is closed; when the high-voltage starter circuit breaker QF is opened, the KM is opened.
The second part is the start signal of the water resistance cabinet. Increase the frequency converter frequency signal into the starting circuit.
The third part is the switchgear allow closing signal. Inverter "high-voltage closing allow K6" string into the high-voltage switchgear QF allow closing circuit, which sent from the controller "high-voltage closing allowed K6" string into the "inverted state" signal.
When the power frequency mode is used, first the QS43/QS44 isolation switch is closed, the DCS starts the QF closing, and after the water resistance tank receives the QF closing signal and the power frequency status signal, the water resistance tank runs, and at this time, the water resistance tank plate is operated. Run from top to bottom, through the water resistance cabinet to achieve a soft rise, when the plate is running to the bottom, there is a limit switch, through the chain, water supply switch contactor KM a signal, so that the water contactor vacuum contactor KM pulls in, shorts out the water resistance and holds, the electrical machinery starts to complete, after delaying a few seconds later, the moving plate automatically resets to the original condition, waits for next time starting.
When operating in variable frequency mode, QS41/QS42 isolation switch is closed first, and DCS starts QF closing. (The water resistance cabinet startup signal is serially connected to the power frequency state. At this time, it cannot be started, nor does the high voltage input QS43 disconnected). The inverter enters the inverter and starts/stops/adjusts the inverter output remotely via the DSC.
At present, for the wire-wound type motor, the water resistance cabinet main cabinet and the water resistance cabinet bypass cabinet are separate and independent, and the high pressure does not pass through the water resistance cabinet, that is, only the control cable enters the water resistance cabinet and the water resistance cabinet outlet control Cable to motor rotor. For squirrel-cage motors, the water resistance cabinet main cabinet and the bypass cabinet are integrated, and a high-voltage cable is connected to the motor stator through the water resistance cabinet.
Second, the movement process water resistance cabinet operation process: the high voltage switch cabinet closing, the water resistance cabinet receives the high voltage switch cabinet closing signal, the water resistance cabinet movement plate starts to run from top to bottom, within the set time The resistance value of the moving plate gradually decreases. When the resistance is close to zero, a vacuum switch in the water blocking cabinet is sucked by a limit switch, the water resistance is shorted, the motor is started, and the delay is delayed. After a few seconds, the movable plate automatically resets to the original state and waits for the next start. If the water blocking cabinet is not completed within a predetermined time, it will send out a fault alarm signal and automatically cut off the switch cabinet to ensure that the motor is not open.
Third, the shortcomings of the water resistance cabinet Water resistance is inefficient, only soft start. If it is used as a speed control, the water resistance cabinet box (liquid resistance part) must be electrified for a long period of time. Once the tank leakage or the liquid resistance is reduced or dry, a production accident or safety accident will occur. And due to the long-term electrification of the liquid resistance of the tank and the serious heat generation, peripheral cooling equipment is required to maintain operation. Therefore, the relative human maintenance costs will also increase.
Fourth, the transformation of water resistance tanks in the actual transformation of the site: Although the water tank resistance exists in the above shortcomings, but customers in the transformation of the water tank resistance will still retain the frequency of water resistance start mode.
(1) There are two types of water resistance cabinets in general. According to the different types of motors, two types of water resistance are connected in series: 1. The water resistance of the rotor string means that the motor is a wound-type motor, that is, the rotor circuit is not short-circuited. At this time, the soft start is gradually realized by changing the resistance value of the rotor circuit in the starting process.
2. The stator string water resistance means that the motor belongs to a squirrel-cage motor, ie the rotor circuit has been short-circuited inside the motor. At this time, soft start is gradually realized by changing the resistance value of the stator circuit in the starting process.
(B) According to the implementation of different ways, divided into two kinds of water resistance 1, the size of the temperature change resistance that is in the start-up process, due to the liquid electrolyte within the liquid temperature increases, the electrolyte molecules activity increased, so that the resistance The value gradually decreases, and the terminal voltage is gradually changed to achieve the purpose of soft start.
2. Increase the plate lift motor in the cabinet. Increase the plate lift motor through the cabinet, change the distance between the input and output plates at a uniform speed, change the size of the resistance value, and gradually change the voltage of the machine terminal to achieve the purpose of soft start.
Note: If the temperature changes the resistance value, it mainly belongs to the stator series water resistance series (ie the squirrel-cage motor).
If the resistance value is changed by the plate lifting motor, the stator and rotor series water resistance can be achieved. At present, the commonly used method is through the pole plate lifting and lowering method to facilitate the control of the start-up process.
Fifth, the internal structure of the water resistance (A) If the resistance is changed by temperature, the interior of the cabinet mainly includes:
1. The bypass cabinet is mainly short-circuited after the startup is completed.
According to the principle of different, and the number of short-circuit contactors, and some water resistance completely dragged after short-circuited, and some short-circuited, the water resistance is still charged.
According to customer needs, choose vacuum circuit breaker or vacuum contactor. The vacuum circuit breaker needs to be divided and closed, and the vacuum contactor is divided into the electrical hold and the mechanical hold type. The electrical hold does not need to add an additional shutoff operation, and the power down is the break, while the mechanical hold needs the shutoff operation.
2. The main body of the water resistance cabinet includes three independent water tanks. Each tank has a fixed copper plate at the bottom. The upper part of the water tank has a fixed copper plate, which leads to a single line. (For squirrel-cage motors: stator water resistance)
According to the size of the motor, the required volume of heat-dissipating liquid is calculated, and the volume of the cabinet body is large or small. For example, if the motor is 10 MW, the body of the water resistance cabinet may reach 10m*2m*4m.
(II) The plate lifts and changes the resistance. The inside of the cabinet mainly includes: a water tank (three-phase separation), a set of plates, a plate lifting motor and the corresponding bearings, and short-circuit contactors (short-circuit contactors are also required by customers Need), PLC, etc.
Sixth, the operation mode (the actual operation of the site based on the data and implementation methods)
(1) Temperature change resistance value 1. After the manufacturer's debugging in the power frequency mode, each plate is immersed in water, and the electrolytic powder according to the calculation is added to the water. At start-up, after power-on, the water temperature rises gradually, the electrolyte activity increases, the resistance between the plates gradually decreases, and the voltage at the motor end gradually decreases from low to high. According to the adjustment time, after the start Short contact vacuum contactor (temperature change resistance is mainly used for squirrel-cage motor), start is completed, water resistance is thrown off. Because of the water resistance of this principle, when the motor is restarted continuously, the start-up characteristics will be different due to inconsistent water temperatures at each restart. In the case of a long startup interval, the start-up characteristics can be basically consistent.
2. After the high voltage in frequency conversion mode, directly short the contactor (shorted contactor action signal is taken from the normally open point of high voltage switch QF0).
(B) Plate lift to change the resistance (focus on the introduction)
1. After the exercise process is finished, the plates are immersed in water and the electrolytic powder based on the calculation is added to the water. Before starting, the upper plate is at the top, and when starting, the upper plate is gradually moved down by the lifting motor. (Some settings are down a few seconds, stop for a few seconds, continue down, repeat). As the distance between them decreases, the resistance between the corresponding two plates decreases, and the voltage at the motor terminal gradually goes from low to high. When the upper plate moves to the lowest limit, the vacuum contactor is short-circuited. At the same time, the upper plate began to rise upwards, and when it reached the maximum limit, the start was completed. In this type of water resistance, when the motor is started continuously, the difference in starting characteristics will not be large, but the servo motor and other components will increase the maintenance work of the water resistance cabinet. (For squirrel-cage and wire-wound motors).
2. Actual data and control logic referenced at the site (1) When the general water resistance is activated, the starting current multiple is between 2 and 3.5 times, and the pressure drop at the grid side can meet the capacity requirement of the upper transformer;
(2) According to the motor size, the starting time is generally set to 20 ~ 40 seconds, the time is generally adjustable, generally more than 40 seconds, the switch cabinet will have anti-time limit protection;
(3) "Water resistance start signal". The general water resistance tanks are now controlled by PLC. The water tank start signal is taken from the corresponding “switch breaker state†of the switch cabinet, that is, the breaker of the customer's switch cabinet. After closing, the PLC of the water resistance cabinet receives the signal, and it starts to start, for example, the plate begins to move downward;
(4) After the breaker of the switch cabinet is opened, the PLC of the water resistance cabinet receives the signal, and the shorted contactor is broken;
(5) That is, the condition of the water resistance switch contactor action is the closing of the high voltage circuit breaker QF0 (taken from the QF0 normally open point).
3. Modifications to be made at the scene after the water resistance cabinet is rebuilt by the inverter (1) Water resistance of the rotor string (Corresponding winding motor, manual bypass)
1 The transformation of the primary circuit is the same as the ordinary frequency conversion transformation;
2 The transformation of the secondary circuit shall lead to a pair of “short-circuit contactor normally closed point†from the short-circuit contactor of the water resistance cabinet and be connected to the “emergency stop†circuit of the inverter. It can be understood as: if the water resistance is short If the contactor is not shorted, the inverter cannot start. It should be noted that the "remote/local" transfer switch must be bypassed when accessing the "emergency stop" circuit. That is, after the rotor of the winding motor is shorted, it is started as a squirrel-cage motor;
3 Water resistance cabinet start conditions are stringed into the power frequency state.
4 field application case introduction. Anhui Huaining Shangfeng Cement adopts the frequency conversion transformation of “rotor string water resistance†mode. The on-site motor parameters are shown in the following table:
motor model
YPKK800-6
Rotating speed
993R/MIN
power
2800KW
Motor manufacturers
Lanzhou Electric Co., Ltd.
Rated voltage
10KV
Water resistance cabinet type
Plate lift changes resistance
Rated current
191.4A
Power factor
0.881
load
B line kiln tail high temperature fan
The site requires water resistance cabinet transformation frequency conversion, and in the frequency mode of operation to retain the water resistance function of the water resistance cabinet, the motor is a three-phase asynchronous winding motor, water resistance cabinet type is increased in the cabinet plate lift motor (that is, plate lift Change resistance). Inverter is a bracket and a manual bypass cabinet. Once the inverter bypass cabinet has the same wiring as the standard wiring, as shown in Figure 1, the 10KV line coming from the customer bus will not pass through the water resistance cabinet (only the customer's AC380V control power to water resistance cabinet).
Fig. 1 Schematic diagram of the rotor resistance water resistance wiring diagram
At this time, in the inverter mode, the short-circuit contactor in the bypass cabinet of the water-resistance cabinet is equivalent to the short-circuit rotor here, so that the winding-type motor is changed into a squirrel-cage motor for use by the frequency converter. In the power frequency mode, after the motor is softened and the soft rise is successful, the short circuit breaker in the bypass cabinet of the water resistance cabinet is equivalent to a shorted rotor here, so that the winding motor is changed into a squirrel cage motor for labor. Frequency use.
When the power frequency mode is used, the QS3 is firstly closed, and the DCS is remotely closed to close the QF circuit breaker. After the water resistance cabinet receives the QF closing signal and the power frequency status, the water resistance cabinet is operated. At this time, the water resistance cabinet plate comes from above. Under running, through the water resistance cabinet to achieve a soft start, when the plate is running to the bottom, there is a limit switch, through the chain, water supply switch cabinet contactor KM a signal, so that the vacuum contactor KM pull in the water resistance cabinet The water resistance is shorted out and maintained, and the winding type becomes the start of the squirrel-cage motor. After a delay of several seconds, the movable plate is automatically reset to its original state, waiting for a next start.
When operating in variable frequency mode, the QS1 and QS2 isolation switches are closed first, DCS starts QF closing, and high-voltage power enters the inverter. (The water resistance cabinet startup signal is serially connected to the power frequency state and cannot be started at this time), while KM water After the switch contactor receives the QF closing signal, the KM directly short-circuits and turns the wire into a squirrel-cage motor. After receiving the KM short-circuit signal, the inverter remotely starts/stops/adjusts the variable-frequency output through the DSC.
In addition, I have also seen an alternative rotor series water resistance and frequency conversion transformation. The user directly opens the rotor connection of the motor and short-circuits the copper directly on the rotor to become a squirrel-cage motor. At this point, the water resistance has been completely thrown off. However, if the inverter fails and the inverter is turned to the industrial frequency, the copper on the rotor needs to be removed (it can't be removed without softening, which is equivalent to the direct power frequency startup of the squirrel-cage motor, leading to the customer's transformer capacity. I can't stand it. It's too much trouble. However, the right of choice rests with the user. The user thinks that the rotor of his/her own will often cause a shotgun phenomenon, so it is appropriate to short-circuit it.
(2) Stator string water resistance (for squirrel-cage motors, manual bypass)
This kind of transformation is relatively complex. The main contents to be determined are as follows:
1 Short circuit breaker. There are at least one short-circuit contactor, and sometimes two or three. For example, it is necessary to inquire about the sequence of closing and opening of the contactors. This must be clarified in the automatic bypass cabinet because it is automatically changed. In the frequency conversion process, it may cause serious consequences. It is necessary to ask whether the self-locking mode of each contactor is electrically maintained or mechanically maintained. In the case of electrical hold, the same signal can be used for opening and closing. If it is maintained mechanically, the opening and closing should be designed separately.
2 Water block start signal. Before the frequency conversion reformation, the water resistance cabinet start signal receives the “circuit breaker normally open point signal†(which is the normally open signal of the busbar high voltage switch cabinet QF0, that is, when the QF0 is closed, normally open becomes normally closed, and the water resistance cabinet starts. If the frequency is softened, if the frequency conversion is modified, it is generally required to increase the inverter's "power frequency status" signal in the circuit that starts the water resistance cabinet start signal. That is, when the power frequency, the water resistance is still normal start, if the frequency conversion, the water resistance cabinet does not move.
3 water resistance shorted signal. Before the frequency conversion reformation, the short circuit signal received by the water resistance cabinet is the “polar plate lower limit position travel switch signalâ€. After the frequency conversion is reformed, it can be changed flexibly according to the requirements. It is necessary to increase the control signal to increase the opening and closing circuit in the closing and opening circuit of the short-circuit contactor. The control method is determined according to customer requirements and system security.
4 field application case introduction. Zaozhuang Quantou Cement Plant adopts the frequency conversion reformation of “stator string water resistance†mode. The on-site motor parameters are shown in the following table:
motor model
YKKP630-6W
Rotating speed
995R/MIN
power
2800KW
Motor manufacturers
Chongqing Saili Meng Motor Co., Ltd.
Rated voltage
10KV
Water resistance cabinet type
Plate lift changes resistance
Rated current
186.6A
load
2# high temperature fan
The schematic diagram of a wiring diagram is shown in Fig. 2. The short contactor in the water resistance cabinet is KM, and the high pressure passes through the water resistance cabinet.
Figure 2 Stator series water resistance wiring diagram
This system is the stator string water resistance, the water resistance cabinet has only one contactor KM, the contactor is the mechanical retention type, the secondary principle change of the system has the following parts.
The first part is that the PLC program changes the logic and leads the line to the KM's split and close coils. The water resistance switch contactor KM control scheme is as follows:
In the power frequency mode, the KM is still controlled by the logic of the water resistance cabinet to achieve soft start.
In the variable frequency mode, when the high-voltage starter circuit breaker QF is closed, the KM is closed; when the high-voltage starter circuit breaker QF is opened, the KM is opened.
The second part is the start signal of the water resistance cabinet. Increase the frequency converter frequency signal into the starting circuit.
The third part is the switchgear allow closing signal. Inverter "high-voltage closing allow K6" string into the high-voltage switchgear QF allow closing circuit, which sent from the controller "high-voltage closing allowed K6" string into the "inverted state" signal.
When the power frequency mode is used, first the QS43/QS44 isolation switch is closed, the DCS starts the QF closing, and after the water resistance tank receives the QF closing signal and the power frequency status signal, the water resistance tank runs, and at this time, the water resistance tank plate is operated. Run from top to bottom, through the water resistance cabinet to achieve a soft rise, when the plate is running to the bottom, there is a limit switch, through the chain, water supply switch contactor KM a signal, so that the water contactor vacuum contactor KM pulls in, shorts out the water resistance and holds, the electrical machinery starts to complete, after delaying a few seconds later, the moving plate automatically resets to the original condition, waits for next time starting.
When operating in variable frequency mode, QS41/QS42 isolation switch is closed first, and DCS starts QF closing. (The water resistance cabinet startup signal is serially connected to the power frequency state. At this time, it cannot be started, nor does the high voltage input QS43 disconnected). The inverter enters the inverter and starts/stops/adjusts the inverter output remotely via the DSC.
At present, for the wire-wound type motor, the water resistance cabinet main cabinet and the water resistance cabinet bypass cabinet are separate and independent, and the high pressure does not pass through the water resistance cabinet, that is, only the control cable enters the water resistance cabinet and the water resistance cabinet outlet control Cable to motor rotor. For squirrel-cage motors, the water resistance cabinet main cabinet and the bypass cabinet are integrated, and a high-voltage cable is connected to the motor stator through the water resistance cabinet.
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