JPH0654568A - Starting control apparatus for three-phase induction motor - Google Patents

Abstract

PURPOSE:To reduce the power consumption at start-up and stabilize a starter by gradually and continuously increasing the low initial voltage in starting a motor and diverting the current to a magnet through electronic switch operation during the motor running. CONSTITUTION:The title apparatus is provided with SCR drive units SCR1-SCR6 in SCR inverse-parallel connection which controls the phase of a three-phase motor M through a three-phase (R, S and T) power supply. It is also provided with a three-contact magnet MT connected in parallel with the SCR drive units; starting controller 10 which controls the operation of the SCR drive units; and sequence controller 11 which controls the operation of the magnet MT. At start-up the low initial voltage is gradually and continuously increased by controlling SCR1 to SCR6 through the starting controller 10; in bypassing after the completion of start-up the sequence controller 11 is turned on and the current is diverted to the magnet MT. This reduces the cost for maintaining and servicing the equipment involved and further lengthens the lifetime of the motor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a start control device for a three-phase induction motor, and more particularly, it separates the start time from the operation time, and at the time of start, a non-contact start by SCR is used to prevent an arc from occurring and to prevent a motor load. By adjusting the starting voltage, the starting efficiency is improved, and at the same time, the stable starting prevents the impact current and extends the life of the electric motor. Also, at the time of operation, when the motor operates at the rated speed after completion of starting,
The starting efficiency is improved so that the system can be operated by bypassing the effective load current below the rated current.

[0002]

2. Description of the Related Art Conventional start-up methods include a Y-.DELTA. Start-up method, which is mainly used at tens of horsepower or less, and a reactor start-up method, which is used at tens of horsepower or more based on the principle of an autotransformer. These start-up schemes reduce the magnitude of the start-up current by lowering the voltage applied to each phase of the motor at start-up to an appropriate value.

However, in such a conventional starting method, since the contacts have to be turned on and off in the state where a current larger than the rated current flows, the contacts are considerably worn due to the arc, especially when the connection state is switched. Since the magnitude of the current changes abruptly, the adverse effect on the power supply and the electric motor due to this could not be eliminated. Therefore, there is a problem that the maintenance and repair cost of the equipment is added and it is impossible to fully protect the electric motor.

[0004]

SUMMARY OF THE INVENTION The present invention has been proposed in order to solve the above-mentioned conventional problems, and it is intended to gradually and continuously increase the initial voltage from a low value at the time of starting the electric motor. Thus, a starting control device for a three-phase induction motor is provided which can reduce power consumption at the time of starting and which can be converted to a magnet by an electronic switch operation during operation, so that the operating rate of the electric motor can be improved by stabilizing the starting device. With the goal.

[0005]

A start control device for a three-phase induction motor according to the present invention is an SC SCR anti-parallel connection for performing phase control of a three-phase motor by supplying three-phase (R.S.T.) power.
In an induction motor starter equipped with an R drive unit, a starting controller (10) for controlling the operation of the SCR drive unit, in which a three-contact magnet (MT) is connected in parallel between both ends of the SCR drive unit, is used for each phase ( R.S.T.) voltage detector (101) for outputting rectangular wave pulse synchronized with voltage phase
And a ramp signal generator (102) for generating a sawtooth wave of a negative potential component synchronized with the voltage phase of each phase, and a phase detector (103) for detecting the phase difference between the input voltage and the current.
And a starter circuit (104) that generates a negative potential integrated voltage over time and the outputs of the phase detector (103) and the voltage detector (101) are compared and an output signal proportional to the value of the difference is generated. The power supply power factor control unit (105) compares the output of the phase detector (103) with the reference voltage, and compares the output of the power supply power factor control unit (105) with the sawtooth wave output of the ramp signal generation unit (102). A comparison unit (106) that generates an output having a different SCR firing angle over time, and an oscillation unit (107) that generates a carrier signal for transmitting the output of the comparison unit (106) to the SCR gate drive unit (108).
And an SCR gate drive unit (1) that receives the outputs of the comparison unit (106) and the oscillation unit (107) as inputs and reduces the voltage level to an appropriate voltage level to output a signal for triggering the SCR.
08), the output of the phase detector (103) due to the bypass of the magnet (MT) when the SCR is energized is sensed and the DC voltage sequence controller (11) is operated to shut off the power supply inside the start controller (10). And a sequence controller (11) for controlling the operation of the three-contact magnet (MT).
Relay contact (RL) that is turned on when the switch is turned on.
-1) and a relay contact (RL-2) that is turned on at the time of bypass after completion of start-up are connected in series, and a starter controller (1
0) and the power supply side (AC220V), an overcurrent breaker (CT) is connected.

[0006]

The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows a connection configuration diagram of a starting control device according to an embodiment of the present invention. This device has a three-phase (RS).
T) SCR anti-parallel connection SCR drive unit (SCR1-SCR) that controls the phase of the three-phase motor (M) by power supply.
6). Further, it has a three-contact magnet (MT) connected in parallel to the SCR drive unit, a start controller (10) for controlling the operation of the SCR drive unit, and a sequence controller (11) for controlling the operation of the magnet (MT).

The starting controller (10) is shown in FIG.
As shown in, the voltage detector (101) that outputs a rectangular wave pulse synchronized with the voltage phase of each phase (R.S.T.) and the saw of the negative (-) potential component synchronized with the voltage phase of each phase. A ramp signal generator (102) that generates a wave and a phase detector (103) for detecting the phase difference between the input voltage and the current.
And a starter circuit (104) that generates a negative potential integrated voltage as time passes, the outputs of the phase detector (103) and the voltage detector (101) are compared, and an output signal proportional to the difference value is output. The generated power source power factor control unit (105) is compared with the output of the phase detector (103) and the reference voltage, and the output of the power source power factor control unit (105) and the ramp signal generation unit (102) are compared.
Comparing the sawtooth wave outputs and generating an output having different SCR firing angles over time, and a carrier signal for transmitting the output of the comparing section (106) to the SCR gate drive section (108). Oscillation part (10
7), the output of the comparing unit (106) and the output of the oscillating unit (107) are received as inputs, the voltage is stepped down to an appropriate voltage level, and the SCR
SCR gate drive unit (108) that outputs a signal for triggering a magnet, and a magnet (MT) when the SCR is energized.
An overlap control unit (109) that senses a change in the output of the phase detector (103) due to bypassing of the power supply, operates the DC voltage sequence controller (11), and shuts off the power supply inside the starting controller (10).
It is composed by.

FIG. 2 shows only the R-phase starting controller, and the S-phase and T-phase starting controllers have the same structure, so the illustration thereof is omitted.

Further, the sequence controller (11), as shown in FIG.
A relay contact (RL-1) that is turned on (ON) and a relay contact (RL-2) that is turned on when bypassing after completion of start-up are connected in series to a magnet (MT), and a start controller (10) and a power supply side. An overcurrent breaker (CT) is connected between (AC220V).

The operation and effect of the thus constructed apparatus of the embodiment will be described with reference to FIGS. 4 to 6.

First, as shown in FIG. 1, the three-phase induction motor (M) has a three-phase input power supply terminal (R.S.T.) and an SCR.
Initial power is supplied through (SCR1 to SCR6).

The above-mentioned SCR power control is based on phase control. Such phase control is detected by the output of the voltage phase of each phase and the phase detector (103) in the ramp signal generator (102) shown in FIG. Voltage and current phase signals (Fig. 4
(See (e) in FIG. 4) is detected and added to the output of the ramp signal generator (102) (see (d) in FIG. 4), and the starting circuit (10)
When the signal integrated in 4) (see (f) in FIG. 4) is input to the power source power factor control unit (105), a proportional voltage is output from the power source power factor control unit (105) due to the load weight when the motor is started ( (See (g) of FIG. 4).

At this time, the starting circuit (104) is composed of an integrating circuit having a negative potential output, and the voltage is increased to the negative potential side as time passes, and the starting time, the initial starting voltage, the starting ramp rate, etc. Can be adjusted.

Further, the power supply power factor control section (105) compares the outputs of the phase detector (103) and the voltage detector (101), produces an output signal proportional to the difference, and controls the starting circuit (104). If the signals to be input are simultaneously input, a phase control voltage depending on time is generated.

Further, if the load of the electric motor is large, the firing angle of the phase control is increased, and if the load is small, the firing angle of the phase control is adjusted to be small.

Thereafter, the comparison section (106) compares the signal detected by the phase detector (103) as shown in (e) of FIG. 4 with the set reference voltage, and the comparison result is output from the power supply power factor control section (105). The output obtained by comparing the signal of (g) of FIG. 4 and the sawtooth wave signal of (d) of FIG.
The firing angle produces another output (see FIG. 4C).

On the other hand, in the oscillating section (107), the comparing section (1
The carrier signal is generated in order to transmit the output of S.06) to the SCR gate driver (108), and when it is applied to the SCR gate driver (108), this is dropped to an appropriate voltage and SC
At the output side of the R gate driver (108), the same signal as in (4) of FIG. 4 is generated, and when applied to each gate side of the SCR, SC
On the output side of the SCR to which R is energized, the same signal as in (c) of FIG. 4 is added to the three-phase motor (M) to perform phase control in the shaded area, so that the starting of the electric motor is controlled.

As described above, when the magnet (MT) is in the bypass state and the SCR is in the conducting state when the SCR is energized, the output of the phase detector (103) changes greatly. Control unit (1
09) to detect the DC voltage sequence controller (1
1) is operated to cut off the power supply to each circuit unit at the timing shown in FIG. 5C to stop the operation.

Here, the on / off switch control unit (1
3) S for operating the AC voltage sequence circuit (15)
The relay contact (RL-1) connected in series with the coil (L) in the magnet (MT) connected in parallel with CR is turned on and off, and the DC voltage sequence controller (11) operates the starting circuit (104). Upon completion, it receives a signal and serves to power the timer (14).

Then, the timer (14) generates an output when the motor is rotated at a rated speed and then stabilizes when the starting circuit (104) by the SCR is completed, and the AC voltage sequence circuit (15) causes the timer (14) to operate. 14), the relay contact (RL-2) connected in series with the magnet coil (L) is turned off, and the main contact (a) of the magnet (MT) is turned on to stop the operation of the SCR. Only the magnet (MT) is operated as in (a).

As shown in FIG. 6, the characteristics of the current at the time of start-up and operation change of the device of the present invention operated in this way are shown in FIG. A stable current that does not have an excessive state flows in the section of point A).

[00023]

As described above, according to the present invention, the maintenance cost of equipment can be reduced by controlling the starting initial voltage of the three-phase induction motor so as to gradually and continuously increase from a low value. it can. Further, the effect of extending the life of the electric motor can be achieved.

[Brief description of drawings]

FIG. 1 is a connection configuration diagram of a start control device according to an embodiment of the present invention.

FIG. 2 is a detailed block diagram of a starting controller according to an embodiment of the present invention.

FIG. 3 is a connection configuration diagram of a sequence controller according to an embodiment of the present invention.

FIG. 4 is a signal waveform diagram for explaining the operation of the controller according to the embodiment of the present invention.

FIG. 5 is a timing chart for explaining start-up and operation timing sequence operation in one embodiment of the present invention.

FIG. 6 is a current characteristic diagram of starting and operating time in one embodiment of the present invention.

[Explanation of symbols]

10: Power on / off and starting controller 13: On / off switch control section 14: Timer 101: Voltage detector 102: Lamp (RAMP) signal generating section 103: Phase detector 104: Starting circuit 105: Power supply power factor control section 106: Comparison unit 107: Oscillation unit 108: SCR gate drive unit 109: Overlap control unit M: Three-phase motor MT: Magnets SCR1 to SCR6: Silicon control rectification terminals (S
CR) CT: Overcurrent breaker RL-1: Operation relay contact when power switch is turned on and off RL-2: Operation relay contact when bypassed after completion of start

Claims (1)

[Claims] 1. An induction motor starter having an SCR drive unit of an SCR anti-parallel connection for performing phase control of a three-phase motor by supplying a three-phase (R.S.T.) power supply. A three-contact magnet (MT) is connected in parallel to the starter controller (1 to control the operation of the SCR drive unit.
0) is a voltage detector (101) that outputs a rectangular wave pulse synchronized with the voltage phase of each phase (R.S.T.) and a sawtooth wave of a negative potential component synchronized with the voltage phase of each phase. A ramp signal generating section (102) for generating, a phase detector (103) for detecting a phase difference between an input voltage and a current, a starting circuit (104) for generating a negative potential integrated voltage over time, Phase detector (103) and voltage detector (1
01), and a power source power factor control section (105) for generating an output signal proportional to the value of the difference, and a phase detector (1
03) output is compared with the reference voltage, and the power supply power factor control unit (10
5) and the sawtooth wave output of the ramp signal generator (102) are compared to generate an output in which the SCR firing angle differs over time, and a comparator (106).
Receives the outputs of the oscillating section (107) and the comparing section (106) and the oscillating section (107) for generating a carrier signal for transmitting the output of the SCR gate driving section (108) to an appropriate voltage level, An SCR gate driver (108) for outputting a signal for triggering the SCR,
Overlap control for detecting the output change of the phase detector (103) due to the bypass of the magnet (MT) when the SCR is energized and operating the DC voltage sequence controller (11) to cut off the power supply inside the start controller (10). And a sequence controller (11) configured to control the operation of the three-contact magnet (MT) and a relay contact (RL-1) that is turned on when the magnet (MT) is switched on.
And a relay contact (RL
-2) are connected in series, and the start controller (10) and the power supply side (AC220
A starting control device for a three-phase induction motor, characterized in that an overcurrent breaker (CT) is connected between V).