JP3342861B2 - Three-phase zero-cross cycle control method and three-phase zero-cross cycle controller realizing the method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention adjusts the amount of power applied to a load by detecting a zero-cross point of a three-phase AC power supply, and more particularly to a heating resistor in an electric furnace connected via a transformer. The present invention relates to a three-phase zero-cross cycle control method for adjusting the amount of applied power and a three-phase zero-cross cycle control device for realizing the method.

In the drawings, the same reference numerals indicate the same or corresponding parts.

[0003]

2. Description of the Related Art Zero-cross cycle control, which has better harmonic characteristics than phase control, is known in a single-phase system, for example, from Japanese Patent Application Laid-Open Nos. 10-280342 and 11-16776 by the present applicant. It is.

FIG. 1 shows an example of the basic configuration of a three-phase zero-cross cycle control device when such a known single-phase zero-cross cycle control is developed into a three-phase zero-cross cycle control.

With this three-phase zero-cross cycle control device,
Consists of two thyristors connected in antiparallel to each other
Three sets of thyristors vs. THR₊, THR1_-; THS₊,
THS _-; THT₊, THT_-But thyristor bridge
A pure resistor triangularly connected to the three-phase AC power supply AC as SB
Connected between the heating resistors R1, R2, and R3.
You. And the zero-cross switching circuit MP has three phases
Connected to AC power supply AC and this thyristor bridge SB
ing. This zero-crossing switching circuit MP
The zero cross point of the three-phase AC power supply AC is detected and this silly
The star bridge SB is fired.

FIG. 2 shows that the phase sequence of the power supply is R-phase → S-phase → T-phase.
And the interphase voltage V_RSChanges from negative to positive
When the zero-cross point is set as the starting point a, the three-phase zero-cross point in FIG.
Entry / exit when the loss cycle controller is energized for one cycle
3 shows a force waveform and the like. (A) shows three of three-phase AC power supply AC
It shows the voltage as seen from the neutral point of the phases R, S, T. (B)
Three-phase voltage V of three-phase AC power supply AC_RS, V_ST, V_TRof
Indicates voltage. (C) shows each of the thyristor bridges SB.
Irista THR₊, THR_-, THS ₊, THS_-, T
HT₊, THT_-And the conduction period when
It is a sequence diagram which shows a conduction period. In this case, the hatch
The period during which power is applied is the conduction period. "_....”
During this period, a firing signal is applied to the gate of the thyristor.
Thyristor voltage is reversed even if
Therefore, this is a period in which the non-conduction is established. From this figure,
Thyristor THR₊And THS_-Fires at the starting point a,
Each time the rear phase angle elapses 60 °, each thyristor
T_-, THS₊, THR_-, THT₊, THS_-In order
It turns out that it fires. (D) shows the heating resistors R1, R
2 and R3 have the same resistance value
This heating resistor generated by the sequence of (c)
Load current i flowing through R1_UVThrough the heating resistor R2.
Load current i_VWAnd the heating resistor R3 is energized.
Load current i_WUIs shown. (E) shows the three-phase AC power supply AC
Input current i that is applied to each phase R, S, T_R,
i_S, I_TIs shown.

As can be seen from FIG. 2, in order to perform zero-cycle energization of one cycle in three phases, a phase angle of 480 is required.
Of the three-phase power supply is energized to the load during the period F (300 °).
At 90 °), only two of the three phases are energized. As can be seen from FIG. 2D, the respective load currents i _UV , i
_VW, i _WU is the effective value slightly larger than the effective value of the cycle in the case of continuous current (i _UV, 3.8% in i _VW, with i _WU
4.7% larger, see equations 1 and 2, respectively). In addition, the load currents i _UV and i _VW are asymmetric on the positive side and the negative side, respectively, and have a DC component (corresponding to about 10.1% of the effective value in the case of continuous energization, see Equation 3).

[0008]

(Equation 1)

[0009]

(Equation 2)

[0010]

(Equation 3)While FIG. 2 shows a case where one cycle of electricity is applied,
FIG. 3 shows input / output waveforms and the like when two cycles of current are applied.
Show. In this case, when conducting electricity for m cycles continuously,
The full period is 360 ° × m + 120 ° in phase angle. Period F
(360 × m−30 °) means that the three-phase AC power
During the period G (90 °) before and after the period F,
Only two of the three phases are energized to the load. Also, each
Load current i _UV, I_VW, I_WUIs the effective value of m
Although slightly larger than the effective value for the cycle, the increase
In comparison with the case of one cycle in FIG.
Become.

From FIGS. 2 and 3, it can be seen that between the S phase and the V phase,
Thyristor vs. THS connected ₊, THS_-Is always
Thyristor vs. THR₊, TH
R_-, THT₊, THT_-Performs the operations shown in FIGS. 2 and 3.
Then, the voltage applied to the load is the same as in FIGS. 2 and 3.
It can be seen that they are the same.

[0012] Figure 4 is a phase sequence is R-phase → S phase → T phase of the power supply, when the inter-phase voltage V _RS is starting from the zero crossing point b and changed to negative from positive, in FIG. 1 6 shows input / output waveforms and the like when the three-phase zero-cross cycle control device is energized for one cycle. The operations shown in FIGS. 2A to 2E correspond to FIGS. 4A to 4E, respectively. Comparing FIG. 2D with FIG. 4D, each waveform has a relationship that the signs are reversed.
A diagram corresponding to FIG. 3 when current is continuously applied for two cycles is omitted in FIG. 4, but is similar to the relationship between FIG. 3 and FIG.

FIG. 5 shows a step-up / step-down circuit which is also triangularly connected between the thyristor bridge SB of FIG. 1 and the triangularly connected resistance heating elements R1, R2, R3 in order to easily adjust the electric furnace to a desired electric power specification. 3 shows a three-phase zero-cross cycle control device when transformers T1, T2, and T3 are connected. However, when the three-phase zero-cross cycle control device shown in FIG. 5 is operated as shown in FIGS. 2 and 3, the output load currents i _UV , i _UV and i
There is a disadvantage that the DC components of _VW (that is, the DC components of the load voltage) are accumulated, and the transformers T1 and T2 are magnetically saturated and damaged. Therefore, conventionally, it has been impossible to realize three-phase zero-cross cycle control using a circuit in which a transformer is installed in a load as shown in FIG.

[0014]

An object of the present invention is to connect a heating resistor via a step-up / step-down transformer while maintaining excellent harmonic characteristics as in the case of a single-phase zero-cross cycle control method. If so, a three-phase zero-cross cycle control method and a three-phase zero-cross cycle control device that can normally apply power to these heating resistors without magnetically saturating the transformer are provided. It is in.

[0015]

According to the present invention, there is provided a camera comprising:
A three-phase zero-cross cycle control method according to claim 2 and a three-phase zero-cross cycle control device according to claims 3 and 4 solve the problem.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 6 shows a three-phase zero-cross cycle control device according to the present invention which solves the above-mentioned disadvantages.

This three-phase zero-cross cycle control device has:
Unlike the three-phase zero-cross cycle control device of FIG. 5, a total of eight thyristors are connected in anti-parallel to each other two by two to form a thyristor bridge SB. And whether the S phase and the V 'phase are always short-circuited by the conductor,
Or, it is made conductive equivalent to the short circuit by an additional thyristor pair. That is, the first thyristor pair T
HR1 ₊ , THR1 ₋ are connected between the R phase and the U ′ phase, the second thyristor pair THT1 ₊ , THT1 ₋ is connected between the T phase and the W ′ phase, and the third thyristor pair THR
2 _+, THR2 _- is connected between the R-phase and W 'phase, and the fourth thyristor pairs THT2 _+, THT2 _- phase T
Phase and the U ′ phase.

In the present invention, a distributed cycle control is described as an example of the zero-cross cycle control method. In this distributed cycle control, the control is executed so that the energized period and the non-energized period are distributed as finely and evenly as possible on the time axis. In the case of the present invention, the continuous energizing period is m cycles (m = 1, 2, 3,...; A natural number), and the continuous non-energizing period is n cycles (n = 1, 3, 5,...; Odd number).

Therefore, when the output power is 100%, m
= ∞, no power interruption period, output power 66.67% (2/3)
, M = 1, n = 1, and 40% (1 / 2.5)
In this case, m = 1 and n = 3. The following table shows the output% and a part of the corresponding energizing period and non-energizing period.

[0021] For example, when the output power is 50%, both the 67% pattern and the 40% pattern in this table appear almost alternately. FIG. 9 shows that the three-phase zero-cross controller of FIG.
5 shows input waveforms and the like when operating at n = 1.

In this case, the zero cross switching circuit M
P detects the phase sequence of the three-phase AC power supply AC at that time, for example, R-phase → S-phase → T-phase when the three-phase zero-cross cycle control device is activated. Then, the zero-cross switching circuit MP defines interphase voltage determined in this detection time, for example, the energization start operation from the zero crossing point a when the phase voltage V _RS is changed to the positive side from the negative side as the mode 1. The zero-cross switching circuit MP is configured such that when energization is required during mode 1, each of the first thyristor pair THR1 ₊ , THR1 ₋ and the second thyristor pair THT1 ₊ , THT1 ₋ of the thyristor bridge SB is provided. A gate signal for performing the mode 1 operation is input to the gate. That is, in this mode 1, as shown in FIG.
Only the second thyristor pair THR1 ₊ , THR1 ₋ and this second thyristor pair THT1 ₊ , THT1 ₋ are activated (see FIG. 7).

As a result, the steady state period F (360 ° × m
−60 °), the three-phase AC power supply (AC) is connected to terminals U ′,
V 'and W' are respectively energized, and before and after the steady-state period F, that is, during the transient state G from the start of the three-phase zero-cross cycle control to 90 °, and before the mode 1 is interrupted. During the 90 ° transient G,
Only two of the three phases are energized.

The circuit configuration and operation described above are similar to those of FIG.
Since each of the load currents i _UV , i _VW , and i _VW during the mode 1 period of FIG. 9D is equivalent to the circuit configuration and operation shown in FIG.
The waveform of i _WV is the load current i _UV , i _VW ,
i Waveforms of _WV coincide with each other.

Next, the zero-cross switching circuit MP
At the end of the energization period in mode 1,
Voltage V_RSZero-cross point when changes from positive to negative
The energization start operation from b is defined as mode 2. Soshi
Therefore, this zero cross switching circuit MP
Thyristor bridging when power is required during
Third SB thyristor pair THR2₊, THR2_-When
Fourth thyristor pair THT2₊, THT2_-Each gate
, A gate signal for performing the operation of mode 2 is input. You
That is, in this mode 2, as shown in FIG.
Third thyristor pair THR2₊, THR2_-And this
Thyristors of 4 vs. THT2₊, THT2 _-Only actuated
(See FIG. 8).

The power supply period in mode 2 is shown in the right half of FIG. At this time, the load current i in FIG.
_UV corresponds to the waveform of the load current _VW in FIG. 4 in which the load current _VW is inverted. The load electric energy i _VW in FIG.
Match _{waveform UV} has positive and negative reversed, and the load current i _WU in FIG. 9 corresponds to the waveform the load current i _WU has positive and negative reversal in FIG.

[0027] Thus, in this manner mode 1 energized load current i _UV between, the load current i _UV with opposite polarity direct current component with respect to the waveform of i _VW, i _VW is, these loads R1,
Since the power is supplied to R2, the positive magnetic flux and the negative magnetic flux in the transformers TR1 and TR2, which generate voltages following these load currents, cancel each other, thereby preventing the occurrence of magnetic saturation.

Although the above description has been given of the case where the phase order is R-phase → S-phase → T-phase, even if the phase order is T-phase → S-phase → R-phase, the R-phase and T-phase are interchanged. Similar considerations are possible.

FIG. 10 is a detailed block diagram of an example of the zero-cross switching circuit MP in FIG. 6 for detecting the zero-cross of the three-phase AC power supply AC and controlling the firing of the thyristor bridge SB to actually realize the above-described operation. is there. Hereinafter, the operation of the zero-cross switching circuit MP will be described in detail with reference to this block diagram.

First, the required output x is a DC signal, and the amount of power applied to the load is set within a range of 0 to 100%. The VF converter 1 outputs the number of pulses proportional to the required output amount x. For example, if the frequency of the three-phase AC power supply is 5
If the output demand x is set to 60% in the 0 Hz area, 30 pulses are output per second, and the pulse interval is 33.3 ms. The output request memo unit 2 stores the output of the VF conversion unit 1 until the shift pulse SP described later is generated. During output, the memo unit 4 outputs the shift pulse S
At the point of occurrence of P, the contents of the output request memo unit 2 are copied, and one cycle (360
°) to the subsequent thyristor control signal generator 8 as to whether or not output is required. The old output memo unit 3 copies the contents of this output memo unit 4 at the time of generation of the shift pulse SP, and 210 ° from the time of generation of the shift pulse SP (the transient state period G
120 ° + 90 ° of the maximum delay from the current voltage) or when the mode switching occurs. The old output memo unit 3 controls the last 120 ° period of the conduction phase angle of 480 ° for one cycle of the three-phase zero-cross output.

When the output of the output memo unit 4 is off, the output of the old output memo unit 3 is on, and the input current signal IS from the current transformer CT in FIG.
The switching unit 5 that has been initialized to the mode 1
A signal for switching from mode to mode 2 is input to the mode memo unit 6. Then, the mode is repeatedly inverted from "1" to "2" and from "2" to "1" each time this signal is input.

In the mode 1, the inter-phase voltage (for example,
V _RS ) from the negative side to the positive side each time passing the zero crossing point, and in the case of mode 2, the inter-phase voltage (for example,
Each time V _RS passes from the positive side to the negative side at the zero cross point, the shift pulse generator 7 outputs one shift pulse SP. Each time this shift pulse SP is output,
The contents of the output memo section 4 are copied to the old output memo section 3,
The contents of the output request memo unit 2 are copied to the output memo unit 4 and the output request memo unit 2 is cleared.

The power supply phase sequence / phase determination unit 9 is a three-phase AC power supply.
Determine the AC phase sequence R → S → T or T → S → R
The result is sent to the thyristor control signal generator 8, while the
A pulse is generated at the time of pressure zero crossing, and a shift pulse is generated.
Six minutes in one cycle every 60 ° starting from SP
The split signal period TS (numbers 1 to 6 in FIG. 9) is generated and shifted.
Output to the pulse generator 7 and the thyristor control signal generator 8.
Power. These intra-cycle time division signals TS are
Lister THR1₊, THR1, THT1₊, THT
1_-, THR2₊, THR2_-, THT2₊, THT2
_-Conduction period and non-conduction period as shown in FIG.
Used to generate the thyristor drive signal SS for controlling the
Used. That is, the old output memo unit 3 and the output memo unit
4 is the first two in-cycle time divisions in one cycle
The signal period TS is sent to the thyristor control signal generator 8 and
The output memo unit 4 has the remaining four hours in one cycle.
The split signal period TS is transmitted to the thyristor control signal generator 8.
Then, the thyristor control signal generating section 8
According to the time division signal period TS in the cycle, eight
Lister THR1₊, THR1, THT1₊, THT
1_-, THR2₊, THR2 _-, THT2₊, THT2
_-Thyristor drive signal SS for turning on / off the gate of
Generate.

The present invention is not limited to a load to which electric power is applied to a heating resistor in an electric furnace, and can be applied to loads for other uses.

[0035]

As described above, according to the present invention, each time one of the modes and the other mode are sequentially executed alternately with the non-energized section interposed therebetween, one of the polarities generated by the load in the one mode is generated. DC component of the other mode and the DC component of the opposite polarity to this one polarity in the other mode are canceled each other, so that excellent harmonic characteristics are maintained as in the single-phase zero-cross cycle control method. In addition, when the heating resistors are connected via a step-up / step-down transformer, power can be normally applied to these heating resistors without magnetic saturation of the transformer.

[Brief description of the drawings]

FIG. 1 shows a basic configuration example of a three-phase zero-cross cycle control device.

FIG. 2 shows a three-phase zero-cross cycle control device of FIG.
It shows input / output waveforms and the like during one cycle operation (interphase V
_The case where the zero cross point when _RS changes from the negative side to the positive side is the starting point).

FIG. 3 shows a three-phase zero-cross cycle controller of FIG.
It shows input / output waveforms and the like when operating in a continuous cycle.

FIG. 4 shows a three-phase zero-cross cycle controller of FIG.
Showing input and output waveforms etc. when cycled (if interphase voltage V _RS is starting from the zero cross point when the change to the negative side from the positive side).

FIG. 5 shows a conventional three-phase zero-cross cycle control device when a heating resistor is connected via three transformers in FIG.

FIG. 6 shows a three-phase zero-cross cycle control device of the present invention.

FIG. 7 shows an equivalent circuit when the three-phase zero-cross cycle control device of FIG.

FIG. 8 shows an equivalent circuit when the three-phase zero-cross cycle control device of FIG.

FIG. 9 shows input / output waveforms and the like when the three-phase zero-cross cycle control device of FIG. 6 operates in mode 1 and mode 2.

FIG. 10 is a block diagram of the zero-cross switching circuit of FIG. 6, which detects zero-cross of the three-phase AC power supply and controls firing of the thyristor bridge.

[Explanation of symbols]

 SB Thyristor bridge AC 3-phase AC power supply R1 Heating resistor R2 Heating resistor R3 Heating resistor MP Zero-crossing switching circuit T1 Transformer T2 Transformer T3 Transformer CT Current transformer 1 V-F converter 2 Output request memo 3 Old output Memo section 4 Memo section during output 5 Mode switching section 6 Mode memo section 7 Shift pulse generation section 8 Thyristor control signal generation section 9 Power supply phase order / phase determination section SP Shift pulse IS Input current signal TS Time division signal period within one cycle SS Thyristor drive signal x required output

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G05F 1/45 H02M 1/08 H05B 3/00

Claims (5)

(57) [Claims] 1. A three-phase alternating current power supply (AC) is connected to an R-phase → S-phase →
The input voltage is input to the terminals R, S, and T of the three-phase alternating current power supply (AC) in the order of T phases, and the input voltage is subjected to three-phase zero-cross cycle control to the load from the terminals U, V, and W to the load. A three-phase zero-cross cycle control method for outputting, comprising:
Thyristor pair (THR1 ₊ , THR1 ₋ )
And a second thyristor pair (THT)
1 _+, THT1 _-) is connected between the T-phase and W-phase, third
Thyristor pair (THR2 ₊ , THR2 ₋ ) has R phase and W
Phase, and a fourth thyristor pair (THT)
2 ₊ , THT2 ₋ ) are connected between the T phase and the U phase, and the thyristor bridge (SB) in which the S phase and the V phase are always short-circuited is used to conduct continuous m cycles (m ≧ 1). And then successive n / 2 cycles (n = 1, 3,
5, ....; odd numbers) are de-energized repeatedly (m ₁ ,
n ₁ , m ₂ , n ₂ ,...), when power is required in one mode (mode 1; mode 2), the inter-phase voltage V _RS changes from negative to positive. starts the power from the changed zero-crossing point, the first thyristor pair (THR1 _+, THR1 _-) and a second thyristor pair (T
HT1 _+, THT1 _-) only is operated, a continuous m
When energization of the cycle is performed between the phase angle of 360 ° × m + 120 °, and when the non-energized section (n ₁ , n ₂ , ...) is reached,
When this one mode (mode 1; mode 2) is changed to the other mode (mode 2; mode 1), and the current needs to be supplied in the other mode (mode 2; mode 1), the phase voltage V _RS starts energization from positively changed zero-cross point from negative third thyristor pair (THR2 _+, THR2 _-) and fourth thyristor pair (T
HT2 _+, THT2 _-) only is operated, a continuous m
The energization of the cycle is performed at a phase angle of 360 ° × m + 120 °, and the one mode (mode 1; mode 2) and the other mode (mode 2; mode 1) alternate with the non-energized section interposed therebetween. A three-phase zero-cross cycle control method. 2. The three-phase alternating current power supply (AC) is changed from a T-phase to an S-phase.
The voltage is input to the terminals T, S, and R of the three-phase AC power supply (AC) in the order of the R phase, and the input voltage is subjected to three-phase zero-cross cycle control. A three-phase zero-cross cycle control method for outputting, comprising:
Thyristor pair (THR1 ₊ , THR1 ₋ )
And a second thyristor pair (THT)
1 _+, THT1 _-) is connected between the T-phase and W-phase, third
Thyristor pair (THR2 ₊ , THR2 ₋ ) has R phase and W
Phase, and a fourth thyristor pair (THT)
2 ₊ , THT2 ₋ ) are connected between the T phase and the U phase, and the thyristor bridge (SB) in which the S phase and the V phase are always short-circuited is used to conduct continuous m cycles (m ≧ 1). And then successive n / 2 cycles (n = 1, 3,
5, ....; odd numbers) are de-energized repeatedly (m ₁ ,
n ₁ , m ₂ , n ₂ ,...), when energization is required in one mode (mode 1; mode 2), the inter-phase voltage V _TS changes from negative to positive. starts the power from the changed zero-crossing point, the first thyristor pair (THR1 _+, THR1 _-) and a second thyristor pair (T
HT1 _+, THT1 _-) only is operated, a continuous m
When energization of the cycle is performed between the phase angle of 360 ° × m + 120 °, and when the non-energized section (n ₁ , n ₂ , ...) is reached,
When this one mode (mode 1; mode 2) is changed to the other mode (mode 2; mode 1), and the current needs to be supplied in the other mode (mode 2; mode 1), the phase voltage V _TS starts energization from positively changed zero-cross point from negative third thyristor pair (THR2 _+, THR2 _-) and fourth thyristor pair (T
HT2 _+, THT2 _-) only is operated, a continuous m
The energization of the cycle is performed at a phase angle of 360 ° × m + 120 °, and the one mode (mode 1; mode 2) and the other mode (mode 2; mode 1) alternate with the non-energized section interposed therebetween. A three-phase zero-cross cycle control method. 3. The three-phase alternating current power supply (AC) is changed from R phase → S phase →
The input voltage is input to the terminals R, S, and T of the three-phase alternating current power supply (AC) in the order of T phases, and the input voltage is subjected to three-phase zero-cross cycle control to the load from the terminals U, V, and W to the load. An output three-phase zero-cross cycle control device, comprising:
Thyristor pair (THR1 ₊ , THR1 ₋ )
And a second thyristor pair (THT)
1 _+, THT1 _-) is connected between the T-phase and W-phase, third
Thyristor pair (THR2 ₊ , THR2 ₋ ) has R phase and W
Phase, and a fourth thyristor pair (THT)
2 ₊ , THT2 ₋ ) are connected between the T phase and the U phase, and the thyristor bridge (SB) in which the S phase and the V phase are always short-circuited is used to conduct continuous m cycles (m ≧ 1). And then successive n / 2 (n = 1, 3,
5, ...; odd number), when repeatedly executing (m ₁ , n ₁ , m ₂ , n ₂ ,...) Control, one of the modes (mode 1; mode) when the energization is required in the state of 2) interphase voltage V _RS starts energization from positively changed zero-cross point from negative first thyristor pair (TH
R1 _+, THR1 _-) and a second thyristor pair (Thtl
_+, Thtl _-) only by operating the energization of successive m cycles performed between the phase angle 360 ° × m + 120 °, the non-energization period _{(n 1, n 2, ......} ) in When this happens, this one mode (mode 1; mode 2) is changed to the other mode (mode 2; mode 1), and it becomes necessary to energize in the other mode (mode 2; mode 1). sometimes,
The energization is started from the zero cross point where the inter-phase voltage V _RS changes from negative to positive, and the third thyristor pair (THR2 ₊ , THR) is turned on.
2 _-) and the fourth thyristor pair (THT2 _+, THT
2 _-) alone is operated, perform the energization of successive m cycled between the phase angle 360 ° × m + 120 °, this one mode (mode 1; mode 2) to the other mode (mode 2; mode 1 ) Are sequentially and alternately executed with the non-energized section interposed therebetween. 4. A three-phase alternating current power supply (AC) is changed from a T-phase to an S-phase.
The voltage is input to the terminals T, S, and R of the three-phase AC power supply (AC) in the order of the R phase, and the input voltage is subjected to three-phase zero-cross cycle control. In the output three-phase zero-cross cycle control device, a first thyristor pair (THR1 ₊ , THR1 ₋ ) composed of two thyristors connected in antiparallel to each other is connected between the R phase and the U phase, Thyristor pair (THT
1 _+, THT1 _-) is connected between the T-phase and W-phase, third
Thyristor pair (THR2 ₊ , THR2 ₋ ) has R phase and W
Phase, and a fourth thyristor pair (THT)
2 ₊ , THT2 ₋ ) are connected between the T phase and the U phase, and the thyristor bridge (SB) in which the S phase and the V phase are always short-circuited is used to conduct continuous m cycles (m ≧ 1). Then, successive n / 2 (n = 1, 3, 5,...)
; Odd number) is repeated (m ₁ , n ₁ , m)
_2, n _2, .....) if you run, one mode (mode 1; when energized is required in the state of mode 2), the zero-crossing point of interphase voltage V _TS is changed from negative to positive From the first thyristor pair (THR1 ₊ , THR1
_-) and the second thyristor pair (THT1 _+, THT1 _-)
Operating only the continuous m cycles of energization by the phase angle
This mode is performed between 360 ° × m + 120 °, and when a non-energized section (n ₁ , n ₂ ,...) Is reached, this one mode (mode 1; mode 2) is switched to the other mode. change in; (mode 2 mode 1), the other mode; when the current is required in the state of (mode 2 mode 1), starts energizing interphase voltage V _TS from positively changed zero-cross point from negative and, a third thyristor pair (THR2 _+, THR2 _-) and fourth thyristor pair (THT2 _+, THT2 _-) only by operating the phase angle 360 ° energization of successive m cycles
× m + 120 °, one mode (mode 1; mode 2) and the other mode (mode 2; mode 1)
And the above-mentioned steps are sequentially and alternately executed with the non-energized section interposed therebetween. 5. At least one thyristor pair is connected between the S phase and the V phase, and the thyristor pair includes:
The three-phase zero-cross cycle control device according to claim 3 or 4, wherein the three-phase zero-cross cycle control device is in a conductive state during the energization period or constantly.