KR20040076378A - Control circuit for stop of hybrid motor starter - Google Patents

Abstract

PURPOSE: A stop control circuit is provided to prevent a water hammering of a pump load caused due to a sudden stop of a motor by smoothly stopping the motor. CONSTITUTION: A stop control circuit comprises a circuit breaker(21) and a mechanical contact unit(29), and an electromagnetic contactor which are connected in serial so as to control the three phase power supplied to a motor(30); a current detection unit(24A) for detecting current of each phase; a line voltage detection unit(24B); a control unit(25) for converting a line voltage into a phase voltage, detecting a zero voltage point based on the converted phase voltage, and generating a phase angle control signal corresponding to load characteristics of the motor; and a semiconductor switch driving unit for controlling operations of a semiconductor switch unit(27) which is connected in parallel to the mechanical contact unit by using the phase angle control signal in such a manner that the motor stops in a smooth manner.

Description

CONTROL CIRCUIT FOR STOP OF HYBRID MOTOR STARTER}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor stop control technology of a hybrid motor starter (HMS). In particular, an electromagnetic contactor and an electronic motor protection relay (EMPR) are connected in series to directly control a motor. In the motor starting and protecting device which starts the motor by a soft starter or the like by a soft starter by changing the star-delta connection, the stop control circuit of the hybrid motor starter which allows the motor to be stopped more flexibly by optimum stop control. It is about.

In general, the motor starts the direct-type start method of supplying the power supply voltage directly to the motor using an electronic switch, and the star connection when the winding of the induction motor is started by using three electronic switches. One of them is the Star-Delta soft starter method, which switches to the delta connection form.

By the way, the direct start method causes a lot of inrush currents to the motor, which not only damages the motor, but also damages the contact portion of the switch.

In addition, the star-delta soft starter method does not cause any inrush current, but requires three switchgear, use a timer or auxiliary switch around, and some motors do not support star-delta connection change. This is not the way to use it in all cases.

On the other hand, when both of the above methods to stop the motor, the motor is stopped by a method of immediately shutting off the power supply, in this case, if the power is cut off immediately under the load of the pump, such as a sudden stop of the motor As a result, a large water hammer occurs, thereby causing a problem of damage to the system.

In order to solve all these problems, it is preferable to use SSSS (Solid-state Switched Soft Srarter) or VVVF (VVVF) controller. The price of such equipment is difficult to apply because it is considerably more expensive than conventional star-delta maneuvered equipment. In addition, SSSS, which is composed only of semiconductor switches, generates heat due to loss of both ends of the switch when current is energized and requires a heat sink to prevent this.

On the other hand, an electric motor protection relay (EMPR: Electronic) that monitors reverse phase, phase loss, unbalance, overload, overcurrent, etc., and protects the motor based on the monitoring result by judging whether there is a problem with the power supplied to the motor. Motor Protection Relay) is used. However, since the motor starting device and the EMPR are usually used in a unit rack form in a panel called a motor control center (MCC), wiring work for connecting these devices to each other is required. do. Therefore, when manufacturing such a unit rack, the wiring work is simple, and as much racks as possible in a given space can greatly reduce the panel manufacturing cost, which can cause a great response to the MCC manufacturer. As a result, there is an urgent need for a device capable of smoothly starting the motor while having a small volume.

1 is a block diagram of a unit rack for an MCC having a start, stop, protect, and monitor function of a motor according to the prior art. As shown therein, three-phase power supply terminals R, S, and T are circuit breakers MCCB. (11) is connected to an electronic motor protection relay (EMPR) 12, the output terminal of the relay unit 12 on the one hand U of the electric motor 16 through each of the three contacts of the power switch 13; , V, W windings, on the other hand, are connected to the windings X, Y, and Z of the electric motor 16 through a driving switch 14 so that each connection point of the starting switch 15 The auxiliary circuit 17 is connected to each of the three contacts, and the auxiliary circuit 17 is connected to the electronic motor protection relay 12 and the three switches 13, 14, and 15 to perform sequence control. This is as follows.

First, referring to the operation when the electric motor 16 is started, when the three contacts of the circuit breaker 11 is shorted (on), thereby power is supplied to the control circuit of the electronic motor protection relay unit 12, where Since the electronic motor protection relay unit 12 continues to monitor the current supplied to the line of the electric motor (16).

In this state, when a command is transmitted from the start switch (push button) connected to the auxiliary circuit 17, the contact point of the power switch 13 and the start switch 15 is short-circuited, whereby the electric motor 16 is a star. It starts to rotate in the form of connection (or Y connection).

At this time, the voltage applied to the connection of the motor 16 is Only the rated voltage of the ship is applied. As such, since the voltage applied to the electric motor 16 is low, the initial inrush current is significantly reduced. However, if the starter switch 15 is opened after a predetermined time has elapsed and the drive switch 14 is shorted, the wiring form of the electric motor 16 is switched to the delta form, and from this time, the motor 16 is turned on. The rated voltage is supplied. For this operation, the auxiliary circuit 17 requires a timer, an auxiliary relay, a push button, and the like.

Next, when the stop command is transmitted from the stop switch connected to the auxiliary circuit 17, the stop operation of the motor 16 immediately opens the power switch 13 and the drive switch 14 at the same time, and the motor 16 Power applied to the power supply is cut off, whereby the electric motor 16 is stopped according to the load torque.

On the other hand, when the electric motor 16 starts to rotate and the electric current starts to flow, the electronic motor protection relay unit 12 continuously checks the phase sequence of the power supply voltage while measuring the current flowing through the electric motor 16 to determine whether it is reversed or normal. Will be judged. If an abnormality is found, the power supply switch 13 is immediately opened to cut off the power supplied to the electric motor 16.

In addition, if the amount of current supplied to the motor 16 increases even more than the specified value and continues for a predetermined time even during starting, the power supply switch 13 is opened to protect the motor 16, and an abnormality in the line connected to the motor 16 is achieved. In addition, even when an image is generated due to an abnormality in the winding of the motor 16 itself, the power supply switch 13 is opened to protect the motor 16.

However, in this conventional technique, the amount of inrush current at start-up can be considerably reduced, but it does not have a complete soft starter characteristic, and the motor is stopped by a method of immediately shutting off the applied power. There was a problem such as a large water hammer due to the sudden stop of the. In addition, three switches, one timer and one auxiliary relay are required, which requires a lot of space for them, and the complexity of the connection for connecting them presents very disadvantageous conditions when mounted in the MCC board. In addition, when the motor is frequently opened and closed, there is a problem that the contact of the switch is easily damaged due to the arc generated at the switch contact. To solve this problem, a soft starter consisting of a solid state switch is used. In this case, the soft starter itself is cheaper than the inverter or the VVVF (about one third) but still has a star It is expensive compared to the delta launch method. In addition, the size of the soft starter composed of the solid state switch also has a bulky defect due to the design considering the continuous operation by the semiconductor switch.

Accordingly, an object of the present invention is to provide an electric motor in a system in which an electronic switch and an electronic motor protection relay (EMPR) are connected in series to directly start the motor or start the motor in a manner such as a soft starter by a star-delta connection change. The present invention provides a stop control circuit of a hybrid motor starter that realizes a flexible stop function at a low cost.

1 is a block diagram of a unit rack for MCC of the electric motor according to the prior art.

2 is a block diagram of a hybrid motor starter according to the present invention.

3 is a detailed block diagram of the controller of FIG. 2;

4 (a)-(h) are HMS operation timing diagrams according to the present invention.

5 is in the present invention Waveform diagram showing a phase detection method for each control.

6A is a conceptual diagram of a soft stop voltage control profile.

6 (b) is an explanatory diagram showing a speed change during soft stop control.

*** Description of the symbols for the main parts of the drawings ***

21: wiring breaker 22: hybrid switch

23 current transformer 24A current detection unit

24B: line voltage detection unit 25: control unit

26: semiconductor switch drive unit 27: semiconductor switch unit

28: display / setting section 30: electric motor

Figure 2 is a block diagram showing an embodiment of a stop control circuit of a hybrid motor starter according to the present invention to interrupt the three-phase power (R, S, T) supplied to the electric motor 30, as shown therein A mechanical circuit breaker (21) of the circuit breaker (21) and the switch which are connected in series; A driving coil SM driven by the control unit 25 to be described later to short-circuit the contacts of the mechanical contact unit 29; A current transformer portion 23 for detecting current of each phase supplied from the circuit breaker 21 to the mechanical contact portion 29; A current detector 24A for detecting current of each phase through each current transformer 23R, 23S, 23T in the current transformer section 23; A line voltage detection unit 24B for detecting a line voltage between each phase supplied to the electric motor 30; A control unit 25 for converting the line voltage to a phase voltage and generating a phase angle control signal so as to detect a zero voltage point based on the voltage to correspond to various motor load characteristics; A semiconductor for controlling the driving of the semiconductor switch unit 27 connected in parallel with the mechanical contact unit 29 by using the phase angle control signal output from the control unit 25 so that the motor 30 can be flexibly stopped. A switch driver 26; In addition to displaying the operation status of the system, a display / setting section 28 for accepting a user's setting value for system control is configured.

FIG. 3 is a detailed block diagram illustrating an embodiment of the controller 25 in FIG. 2, and as shown therein, a phase voltage delayed by a predetermined phase and outputted by a predetermined phase as detected by the line voltage detector 24B. A conversion unit 301; A zero voltage detector 302 for detecting a zero voltage crossing point of time with respect to the output voltage of the phase voltage converter 301; A sawtooth wave generator 303 for generating a sawtooth wave on the basis of the zero voltage detection point; A comparison unit 304 for comparing the sawtooth wave output from the sawtooth wave generator 303 with an output signal of the phase angle control voltage generator 310 to be described later and outputting a gate voltage according thereto; An AND gate 305 for and combining the gate voltage output from the comparator 304 with the output signal of the pulse generator 311; An AND gate 306 for AND-combining the gate control signal output from the sequence controller 312 and the output signal of the AND gate 305 to the semiconductor switch driver 26; A half cycle current integration calculation unit (307) for integrating a current value during the half cycle based on the detected current in the current detector (24A) and the zero voltage crossing detection result of the zero voltage detector (302); Receives the current value and the starting current profile during the half cycle, and for a smooth start through a predetermined calculation process A flexible starting control unit 308 for generating each control signal; On the basis of the integrated current value output from the half-cycle current integration calculation unit 307 and the voltage control profile output from the stop voltage profile generator 314, for the flexible stop operation of the motor 30 A flexible stop controller 309 for generating each control signal; The phase angle control voltage generator which selects an output signal of the flexible start controller 308 or an output signal of the flexible stop controller 309 according to the selection signal output from the sequence controller 312 and transmits the output signal to the comparison unit 304. 310; A pulse generator (311) for generating a pulse for loading and outputting the gate voltage output from the comparator (304) to the output signal of the pulse generator (311); A sequence control unit 312 for outputting a selection signal for flexible starting and stopping by operation sequence control according to a user's request; A starting current profile generator 313 for providing a starting current profile to the flexible starting controller 308 under the control of the sequence controller 312; A stop voltage profile generator 314 for generating a voltage control profile by performing a predetermined calculation function under the control of the sequence controller 312; An operation state display control unit 315 performing a control function for displaying an operation state on the display / setting unit 28 under the control of the sequence control unit 312; The driving state monitoring / protecting unit 316 monitors the driving state for safe driving and notifies the stop voltage profile generator 314 of the detected signal when an abnormal state is detected. When described in detail with reference to Figures 4 to 6 attached the action and effect as follows.

3 is a control block diagram for a soft starter and a soft stop according to the present invention, which shows a detailed implementation of the control on R in the hybrid motor starter (HMS) 22 of FIG. The remaining S and T phases also have the same structure, and each phase difference is 2 Since it is generated by / 3, the final control signal is also applied to each phase with the same phase difference. Therefore, in describing the operation of the present invention, the R phase is described as an example.

In a state in which the control power is secured to the hybrid switch 22 by the contacts 21R, 21S, 21T of the circuit breaker 21 being shorted, a run / stop switch (Run / Stop switch) is used to drive the electric motor 30. / Stop) to the run position, the control unit 25, the run control signal (a) of FIG. ) Is entered.

At this time, the controller 25 is the run control signal ( ) And the driving voltage SM as shown in FIG. ) In the actual system, the driving voltage (SM) is applied to the driving coil SM. Since a relay contact is frequently used as a switching device for applying), as shown in FIG. After having a delay time by), the driving coil SM is operated.

At the moment when the mechanical contacts 29X, 29Y, 29Z, which are main contacts of the switch, are shorted by the driving coil SM, a lot of inrush current flows to the electric motor 30 serving as a load. At this time, the current detector 24A detects the inrush currents of the R, S, and T phases through the current transformer 23R, and the line voltage detector 24B detects the line voltages of the phases. , , ).

The line voltage detected by the line voltage detection unit 24B ( , , ), The line voltage V_RS is converted by the phase voltage converter 301. Delayed phase voltage ( The zero voltage detection unit 302 detects a zero voltage crossing time point therefrom. The sawtooth wave generating unit 303 is a sawtooth wave as shown in FIG. ) Is supplied to one input of the comparator 304.

As described above, the reason why the sawtooth wave is generated based on the zero voltage crossing point for the phase voltage of each phase is RST 3 of the bidirectional semiconductor switch (for example, SCR and TRIAC) 27R compared to the output voltage by current control. This is to perform phase angle control on the phase.

The half cycle current integration calculation unit 307 integrates the current value during the half cycle based on the detection current in the current detection unit 24A and the zero voltage crossing detection result of the zero voltage detection unit 302. In order to softly start the electric motor 30 by appropriately controlling the semiconductor switch 27R based on the integrated current value, the flexible start control unit 308 is the following [Equation 1], [Equation 2]. ]in Each control function is performed, and the voltage command value V (t) is provided to the other input of the comparator 304 through the phase angle control voltage generator 111.

here,

Looking at Equation 1, V (0) = 0, V (t) then controls the driving of the semiconductor switch 27R at an arbitrary angle so that the semiconductor switch 27R starts to drive. While the integrated value Idc of the measurement current by the half-cycle current integration calculation unit 307 is smaller than Idcref, V (t) continues to increase, and when Idc becomes larger, As a result, V (t) is no longer increased, and as a result, the load current of the motor 30 is limited to the value of Idcref.

Here, Idcref is a value corresponding to several hundred percent of the rated current of the motor 30, and is limited to a value much smaller than the direct current, so that the power supply is not overloaded, and at the same time, it is set to a value capable of flexible starting. In addition, if the speed increases near the rated speed due to the characteristics of the motor 30, the load current drops sharply, so that Idc becomes smaller than Idcref. Accordingly, even at this time , So eventually at normal speed Operation at each angle completes the soft start operation.

On the other hand, the control process for the flexible stop operation of the electric motor 30 will be described with reference to FIGS. 3, 5 and 6 as follows.

In FIG. 3, the half cycle current integration calculation unit 307 integrates the current value during the half cycle based on the detection current of the current detection unit 24A and the detection result of the zero voltage detection unit 302 as described above. Is output to the flexible start control unit 308 and the flexible stop control unit 309.

In addition, the stop voltage profile generator 314 calculates the following Equations 3 to 5 to generate a voltage control profile as shown in FIG. The voltage value for generating the voltage control profile as shown in FIG. 6A in the stop voltage profile generator 314 And time value Is input by the user through the display / setting unit 28.

here,

For reference, the K1 to K5 is the average value of the load current of the motor 30 in the steady state ( This value depends on), which is dependent on the type of load of the motor 30 and is determined experimentally.

Accordingly, the flexible stop control unit 309 based on the integrated current value output from the half-cycle current integration calculation unit 307 and the voltage control profile output from the stop voltage profile generator 314, the motor 30. For flexible stop motion Each control signal is generated and output to the phase angle control voltage generator 310.

On the other hand, the sequence controller 312 outputs a selection signal OPER_SEL for flexible start and stop to the phase angle control voltage generator 310 according to a user's request according to the operation sequence control shown in FIG. 4. Accordingly, the phase angle control voltage generator 310 selects an output signal of the flexible start controller 308 or an output signal of the flexible stop controller 309 according to the selection signal OPER_SEL, and performs a control operation accordingly. You lose.

The comparison unit 304 compares the sawtooth wave output from the sawtooth wave generation unit 303 with the output signal of the phase angle control voltage generation unit 310 as shown in FIG. ), ( ), ( )

The AND gate 305 is connected to the gate voltage at the comparison unit 304. Outputs the pulse generator 311 while being output to " high ". In addition, the AND gate 306 of the next stage receives the output signal of the AND gate 305 to the semiconductor switch driver 26 as it is when the gate control signal SCR_BLOCK is input “high” from the sequence controller 312. Will be delivered at this time Each control is made. However, when the gate control signal SCR_BLOCK is input to the AND gate 306 as "low", the output signal of the AND gate 305 is cut off and the driving of the semiconductor switch driver 26 is stopped.

The sequence controller 312 generates the gate control signal SCR_BLOCK based on the signal TRIP_SIGNAL input from the operation state monitor / protector 316 and the output signal RUN / STOP of the run / stop switch.

As described in detail above, the present invention provides an electric motor in a system in which an electronic switch and an electronic motor protection relay (EMPR) are connected in series to directly start the motor or start the motor by a soft starter by a star-delta connection change. By making it possible to stop very flexibly, there is an effect that can prevent the water hammer phenomenon of the pump load due to the sudden stop of the motor.

Claims (4)

A circuit breaker 21 and a mechanical contact portion 29 of the switch, which are connected in series for interrupting three-phase power supplies R, S, and T supplied to the electric motor 30; In a hybrid motor starter composed of a current detector 24A for detecting a current of each phase and a line voltage detector 24B for detecting a line voltage, the line voltage is converted to a phase voltage, and a zero voltage point is detected based on this. A control unit 25 for generating a phase angle control signal so as to correspond to various load characteristics of the electric motor 30; By using the phase angle control signal, the semiconductor switch driving unit 26 for controlling the driving of the semiconductor switch unit 27 connected in parallel with the mechanical contact unit 29 so that the motor 30 is stopped flexibly. Stop control circuit of a hybrid motor starter, characterized in that configured. The electronic device of claim 1, wherein the controller 25 comprises: a phase voltage converter 301 for delaying the line voltage by a predetermined phase and outputting the delayed line voltage; A zero voltage detector 302 for detecting a zero voltage crossing point in the output voltage of the phase voltage converter 301; A sawtooth wave generator 303 for generating a sawtooth wave on the basis of the zero voltage crossing detection time point; A comparison unit 304 for comparing the sawtooth wave with an output signal of the phase angle control voltage generator 310 to be described later and outputting a gate voltage according thereto; An AND gate 305 for and combining the gate voltage output from the comparator 304 with the output signal of the pulse generator 311; An AND gate 306 for AND-combining the gate control signal output from the sequence controller 312 and the output signal of the AND gate 305 to the semiconductor switch driver 26; A half cycle current integration calculation unit (307) for integrating a current value during the half cycle based on the detected current in the current detector (24A) and the zero voltage crossing detection result of the zero voltage detector (302); It is supplied with the current value and starting current profile for the half cycle, A flexible starting control unit 308 for generating each control signal; Receiving the integrated current value and the stop voltage profile, for the flexible stop operation of the motor 30 A flexible stop controller 309 for generating each control signal; The phase angle control voltage generator which selects an output signal of the flexible start controller 308 or an output signal of the flexible stop controller 309 according to the selection signal output from the sequence controller 312 and transmits the output signal to the comparison unit 304. Stop control circuit of a hybrid motor starter, characterized in that it comprises a (310). The method of claim 2, wherein the flexible starting control unit 308 is the following equation (1), [Equation 2] Stop control circuit of a hybrid motor starter, characterized in that to perform each control function. [Equation 1] [Equation 2] here, 3. The stop control circuit of a hybrid motor starter according to claim 2, wherein the stop voltage profile is calculated by the following [Equation 3]-[Equation 5]. [Equation 3] [Equation 4] [Equation 5] here,