CN101501983A - Variable voltage supply system - Google Patents

Abstract

Apparatus for controlling the voltage supplied to a load, comprising: a multi-phase transformer having a primary and a secondary winding for each phase, each secondary being connected in series between an input line and an output directed to the load; and the primary is configurable by switches such that the phase of the voltage of the secondary is different from the line to which it is connected by a phase different from 0 and 180 degrees.

Description

Variable voltage supply system

Technical field

The present invention relates to provide variable voltage, for example provide a kind of and be applicable to actuating motor and the variable voltage system of service meter when load reduces.

Background technology

When induction motor moved, they supplied with back electromotive force (back EMF) voltage.Do not have back electromotive force during starts, the input impedance of motor is lower relatively and surge voltage is very high.This makes and draw unnecessary electric current from power supply (line).This not only requires motor designs is become to stand these circuits, and requires circuit that these big electric currents must be able to be provided.

Many solutions have been suggested and have been used for low voltage during starts being provided and improving voltage along with the increase of electromotor velocity.

A kind of method is " star-delta " configuration, in " star-delta " configuration motor from three-phase transformer carry out feed and when motor quickens the winding of motor switch to triangle connection from Y-connection to power line.This provides two step voltages that are used for actuating motor.This method is subjected to the influence of following shortcoming:

1. only there are two voltage levels and have conversion (commutation) effect that causes due to voltage spikes from a kind of configuration transitions to another kind during the configuration.

2. between power controller and motor, need 6 wires.

3. even equal electric current on the supply line at motor line electric current during starts.

4. the contactor that switches between two kinds of patterns transmits all motor currents.

5. need auxiliary big resistor to allow electric current continuous between transfer period.

Second method utilizes tapped autotransformer to change voltage.In this method, voltage supplies to motor via having multitap decompression autotransformer.Motor at first is connected to minimum tap, and along with motor quickens, the input of motor is transferred to high voltage successively by the tap that changes service voltage then.This method is subjected to many different defect influence.One is to require to switch when changing voltage the whole power that just are being utilized.Second coil and starting current that must be designed to transmit motor unshakable in one's determination that defective is a transformer.This makes transformer very big and expensive, and the size that its size is similar to motor itself is common.The 3rd defective is: owing to when changing tap, disconnect output, so there is serious transformation problem.For this reason, do not use this method widely.The 4th, contactor must transmit whole electric currents when switched voltage.

The third method utilizes phase control to change voltage.In this method, control voltage and the open phase of thyristor is used for changing the voltage that is transported to output with thyristor (thyristor).It is well-known that this method is not carried sinusoidal voltage and its poor efficiency aspect actuating motor.Particularly, there is intrinsic phase delay, especially during starts and more obvious between the power when thyristor is opened predation transient period.And, can not use capacitor to improve power factor usually by phase control.

Another problem that occurs in the control of induction process is that induction motor is the most effective at full load.When load is reduced, the still very high and decrease in efficiency of core loss.Be well known that the voltage that reduces on the induction motor can make operating efficiency higher when load is lower than rated value.Yet the practical way of implementing this variation is also not known.

Israel's patent 133307 that 199_ submitted at December 5 has been described a kind of system of the control that is used to throw light on, wherein primary winding (primary) crosses over that input is provided with (between " circuit " and " return road " connection) and secondary winding (secondary) is connected between load and the circuit, and the disclosure of this patent incorporated herein by reference.Secondary winding is wound and connects with the line voltage of antagonism (thereby minimizing) to the load supply.This is provided at the voltage that load place reduces.When the needs full voltage, the transformer input is broken from the return road and by short circuit, forcing the voltage on the secondary winding is zero.Then, secondary winding can be by short circuit.Can supply with a plurality of transformer stage so that the bigger variation of load voltage to be provided.For three-phase, this configuration is repeated three times.

Summary of the invention

An aspect of some embodiments of the present invention relates to load supplies with the voltage that changes, and plural thus different voltages are provided for load, and need not to use active element and do not have transformation problem substantially.

As used herein, term " and need not to use active element " etc. mean not active device is used to import such as transistor and thyristor and load between power path.

In aspect this invention is more wide in range, power input is three-phase power input and power path comprises the secondary winding of three-phase transformer, and the elementary winding of this three-phase transformer is configurable so that the phase place of the voltage of secondary winding and connected circuit differ one and be different from 0 degree and 180 phase places of spending.

In one embodiment of the invention, elementary winding is switchable between at least two positions, and at least one in described at least two positions is: (1) position, wherein elementary winding are connected between two inputs mutually; (2) positions, wherein elementary winding are connected between the first input phase and the neutral point; (3) positions, wherein elementary winding are connected between the second input phase and the neutral point.Preferably, in the 4th configuration (4), elementary winding is disconnected and the short circuit alternatively of secondary winding quilt.This configuration can provide at least four different output voltages.As used herein, term " neutral point " means actual or virtual neutral point, the i.e. point of formed nearly no-voltage when an end of these phases is joined together.

In one embodiment of the invention, when actuating motor, elementary winding is connected between the phase identical with the feed secondary winding and second phase.The output voltage of specific phase is the input voltage of this phase and the voltage between phases sum after the conversion.This voltage can be greater than input voltage or less than input voltage.For motor start-up, use can reduce the winding configuration of voltage.For example, suppose input voltage be 400V (between line) and transformation ratio be 400V than 100V, output voltage is 253V (zero load) between the line that finally obtains.If elementary winding switches to neutral point mutually from second, output voltage is enhanced 298V (zero load) between line.Note, owing to secondary winding remains attached between the input and output, so there is not the voltage of transformation that produces by this variation.Alternatively, cross over elementary winding buffer or other spikes minimizing circuit are set.

Then, elementary winding is switched and crosses over second phase and the neutral point.Output voltage is 356V (zero load) between the line that finally obtains.Then, disconnect elementary winding and short circuit secondary winding from input.Output voltage is now identical with input voltage, i.e. 400V.

By selecting other transformation ratios, can obtain other voltage levels.In addition, by changing the closure of elementary winding, can obtain to be higher than the auxiliary voltage of input voltage.Under described situation, except 400V, can also obtain 600,515 and the voltage of 460V.Also can obtain other voltages by other connections.

Notice that transformer is the power of the little percentage that utilized by load of conversion only.Thereby, transformer can less than existing variable power method such as star-delta method and tapped autotransformer method in employed transformer.

In the second embodiment of the invention, execution switching and acquisition input voltage step still less still less.

In some embodiment of this invention, as indicated in above, elementary winding is connected directly crosses over incoming line and secondary winding is connected in series in the load-side that is connected in parallel of elementary winding.In the alternate embodiment of this invention, secondary winding be connected in series to the line side and elementary winding be connected in load-side in parallel, be positioned at after the secondary winding.In another alternate embodiment of this invention, a side of each elementary winding is connected to the line side of secondary winding and the opposite side of elementary winding is connected the load-side of secondary winding.

An aspect of some embodiments of the present invention relate to when load variations, be adjusted to motor voltage so that more effective work to be provided.Be well known that when the mechanical output of being supplied with by motor was lower than its rated power, induction motor can be operated in the voltage lower than its rated voltage.When with the work of this low voltage, the power of electric motor factor is enhanced, cause motor and transformer than low-loss and to the less destruction of electric power system.

In one embodiment of the invention, measurement is by the power of electric motor that is fed into of power feed.Then, use above-described method alternatively, this voltage be reduced to will be improved power factor simultaneously still with the voltage of the electric current supply power of the rated current that is lower than motor and transformer.

Though this invention is described with regard to the situation of three-phase system, some feature of this invention (utilizing less voltage level) also can be applicable to binary system and also can be applicable to voltage change power in the single phase system.

Thereby, according to an embodiment of this invention, a kind of equipment that is used to control to the load service voltage is provided, this equipment comprises: polyphase transformer, it has the primary and secondary winding that is used for every phase, each secondary winding be connected in series in incoming line and with output that this load is connected between; And elementary winding is configurable by switch, so that the circuit that the phase place of the voltage of secondary winding is connected to it differs a phase place that is different from 0 degree and 180 degree.

In one embodiment of the invention, these switches comprise: a plurality of switches, it is switchable to switch the input of each elementary winding, so that their are with comprising that in the various configurations of at least a configuration more than one carry out selectivity and connect, and each elementary winding is connected at least a configuration:

(a) in the input that connects with its secondary winding mutually and between another input phase;

(b) in the input that connects with its secondary winding mutually and between neutral point or the dummy neutral;

(c) be different between the input two-phase mutually that connects with its secondary winding; With

(d) be different between the input phase and neutral point or dummy neutral mutually that connects with its secondary winding.

In one embodiment of the invention, a plurality of switches can also the elementary winding of (e) short circuit.Alternatively, for (e), corresponding secondary winding is also by short circuit.

In one embodiment of the invention, elementary winding and secondary winding (a) each line voltage in (d) that is configured to make the voltage of output be lower than.

In one embodiment of the invention, a plurality of switches are switchable switching the input of each elementary winding, so that they are connected by selectivity between in (a) to (d) two, three or all.

In one embodiment of the invention, (a) only carry out about the elementary winding of transformer to the switching of (d).

In one embodiment of the invention, in (a) to (d), switching between the item arbitrarily, needn't switch in the circuit between input and load.

In one embodiment of the invention, with regard at least a configuration of these switches, the voltage of output is higher than line voltage.

In one embodiment of the invention, these switches can be put upside down at least a polarity in these connections.

In one embodiment of the invention, polyphase transformer is a three-phase transformer, and input is a three-phase voltage source.

In one embodiment of the invention, the input of the direct crossover track of elementary winding connects and secondary winding is connected in series to circuit and is positioned at the load-side that is connected in parallel.

In the alternate embodiment of this invention, the input of secondary winding and line is connected in series and elementary winding is connected in parallel to the circuit of the load-side that is positioned at secondary winding.

In the another alternate embodiment of this invention, a side of each elementary winding is connected the line side of secondary winding, and the opposite side of elementary winding is connected the load-side of secondary winding.

An embodiment according to this invention further provides a kind of voltage method that changes to load, and this method comprises: connect the equipment according to this invention between heterogeneous input and load;

By with the corresponding different configurations of the different voltages of crossing over secondary winding between sequentially switch elementary winding, make output voltage change at least one grade (step).

Alternatively, output voltage changes to high voltage step by step from low voltage.

Alternatively, measure the characteristic of this load, and wherein when this characteristic reaches given standard, stop the voltage rising.

Alternatively, this load is an induction motor.

An embodiment according to this invention further provides a kind of voltage method that changes to induction motor, and this method comprises:

The equipment of the power that is used to be controlled to load is connected between input and the induction motor;

Under given voltage, measure the characteristic of this induction motor;

Based on this characteristic, determine that improving voltage still is reduction voltage; With

In response to determining, change output voltage.

Alternatively, described equipment is the equipment according to this invention.

Alternatively, the mean-square value of input line voltage (RMS) is greater than 270V.

Alternatively, this load is a threephase motor.

Description of drawings

Provide the detailed description of following specific non-limiting example to this invention, further to illustrate this invention and to be shown as the optimal mode that is used to implement this invention known for inventor.

This detailed description should be read in conjunction with following accompanying drawing.Under usable condition, identical label is used to refer to same or analogous element of generation in different figure.

Fig. 1 is the basic circuit diagram according to the drive system of the excited electric motor of an exemplary embodiment of invention;

Fig. 2 is the circuit diagram according to transformer and related switch in the drive system of an embodiment of invention;

Fig. 3 A and Fig. 3 B are respectively at being connected and polar plot of the circuit of Fig. 2 of first configuration, obtain minimum voltage under this first configuration;

Fig. 4 A and Fig. 4 B are respectively at being connected and polar plot of the circuit of Fig. 2 of second configuration, obtain first high voltage under this second configuration;

Fig. 5 A and Fig. 5 B are respectively at being connected and polar plot of the circuit of Fig. 2 of the 3rd configuration, obtain second high voltage under the 3rd configuration;

Fig. 6 A and Fig. 6 B are respectively at being connected and polar plot of the circuit of Fig. 2 of the 4th configuration, are transported to motor at the 4th configuration voltage that rolls off the production line;

Fig. 7 is the circuit diagram according to transformer and related switch in the drive system of an embodiment of invention;

Fig. 8 is the circuit diagram according to transformer and related switch in the drive system of another embodiment of invention; With

Fig. 9 is the flow chart of the voltage of control of induction with the method for the load voltage on the coupling motor.

Embodiment

Fig. 1 is the basic circuit diagram according to the power controller (drive system) 100 of the excited electric motor 102 of an exemplary embodiment of invention.As shown in the figure, power controller 100 receive three-phase power at phase L1, L2 and L3 place with first voltage and with variable output voltage in that U, V and W place deliver power to motor 100 mutually.Motor driven load 104.Neutral point N can be supplied to motor.The work of controller 106 power controlling controllers and can respond input from optical measurement module 108, this will make an explanation below.

Fig. 2 shows some details of the circuit of the power controller 100 in an exemplary embodiment of invention.Power controller comprises three-phase transformer with its simplest form, and this three-phase transformer has winding and secondary winding S1, S2 and the S3 that is designated as P1, P2 and P3.Secondary winding is connected in series between online input and the load.In addition, power controller comprises a plurality of threephase switch K1, K2, K3 and K4, and these switches are used for connecting by different way elementary winding crossover track input effectively.

In addition, optionally threephase switch K6 is used for short circuit secondary winding under certain conditions.

The main configuration of these switches of explanation in the following drawings.

Fig. 3 A and Fig. 3 B are respectively that minimum voltage is transported to load under this first configuration at being connected and vectogram of the circuit of Fig. 2 of first configuration.

Fig. 3 A shows the circuit of Fig. 2 when closed and other switches of K switch 1 and K3 disconnect.In this configuration, P1 connects online phase 1 and line mutually between 2, and P2 connects online phase 2 and line mutually between 3 and P3 connects online phase 3 and line mutually between 1.

With the circuit that is connected with secondary winding 30 ° of phase differences are arranged owing to be applied to the phase place of the voltage on the elementary winding, so cause the phase diagram shown in Fig. 3 B.For instance rather than restriction invention, suppose that 400/100 elementary-secondary ratio and supposition input voltage is 400V (volt).

For shown in winding direction for, the alternate output voltage U, V, the W that finally obtain are 253V.

Fig. 4 A and Fig. 4 B are respectively at being connected and polar plot of the circuit of Fig. 2 of second configuration, are transported to load at this second configuration next but one high voltage.

Fig. 4 A shows the circuit of Fig. 2 when closed and other switches of K switch 1 and K4 disconnect.In this configuration, each all is connected between its own phase and the neutral point among P1, P2 and the P3.Alternatively, this connection can be to actual neutral point or to by an end of transformer is connected to the dummy neutral N ' that identical point forms.

Owing to be applied to the phase place of the voltage on the elementary winding and the circuit homophase that is connected with secondary winding, so cause the phase diagram shown in Fig. 4 B.For instance rather than restriction invention, suppose that 400/100 elementary-secondary ratio and supposition input voltage is 400V.Because the voltage on each P winding is 253V, so secondary voltage is 63V, with input line voltage out-phase.So voltage between phases U, V, W are 289V.

Note, when between the configuration of the configuration of Fig. 3 A and Fig. 4 A, switching (hope is break-before-make), although, can not interrupt the electric current of motor because elementary winding is opened a way thereby secondary winding temporarily provides high impedance.Alternatively, cross over elementary winding buffer or other spikes minimizing circuit are set.

Fig. 5 A and Fig. 5 B are respectively at being connected and polar plot of the circuit of Fig. 2 of the 3rd configuration, are transported to load at the 3rd configuration next but one high voltage.

Fig. 5 A shows the circuit of Fig. 2 when closed and other switches of K switch 2 and K3 disconnect.In this configuration, each all is connected between another phase and the neutral point among P1, P2 and the P3.

With the circuit that is connected with secondary winding 60 ° of phase differences are arranged owing to be applied to the phase place of the voltage on the respective primary winding, so cause the phase diagram shown in Fig. 5 B.For instance rather than restriction invention, suppose that 400/100 elementary-secondary ratio and supposition input voltage is 400V.Because the voltage on each P winding is 253V, so secondary voltage is 63V.So voltage between phases U, V, W are 356V.

Fig. 6 A and Fig. 6 B are respectively that input line voltage is transported to load under the 4th configuration at being connected and polar plot of the circuit of Fig. 2 of the 4th configuration.

Fig. 6 A shows the circuit of Fig. 2 when closed and other switches of K switch 2 and K4 disconnect the closure alternatively except K switch 6.In this configuration, each is all opened from line interruption and by short circuit among P1, P2 and the P3, and secondary winding is also alternatively by short circuit.Thereby, there is not significant voltage antagonism input line voltage, this voltage is that 400V is applied directly on the motor.

Be appreciated that it is not indispensable making the secondary winding short circuit.Yet they are preferably by core loss and/or the conduction loss of short circuit to avoid transformer.

Less if desired electric pressure then can reduce the number of switches of elementary winding side.For example, if K3 and K4 are replaced by short circuit, then closed K1 allows K2 and K6 disconnection will cause the configuration of Fig. 3 A and will supply with the voltage of 253V to load simultaneously.Disconnect K1 and short circuit K2 and alternatively short circuit K6 will cause the configuration of Fig. 6 A and will be transported to load to input line voltage.

So far, the present invention just is described to the situation that load provides the voltage of being less than or equal to line voltage for example to be used to start induction motor.Yet if for example make the winding (perhaps elementary winding connects or secondary winding connects) on the transformer reverse by the connection of putting upside down elementary winding, similarly configuration can be used for providing one or more voltages higher than line voltage to load.This type of configuration may be under need the situation that higher voltage starts than working voltage or is being considered to wish that under the situation of multivoltage level more be useful.Provide intergrade may need more switches.

Similarly, by switching elementary winding in a different manner, for example, can obtain more intermediate voltage by elementary winding is connected between the phase different with secondary winding.Yet be noted that shown in preferred embodiment in, all switchings all are not have switch in the low current side in main current path.

In the above among the embodiment shown in Fig. 2 of Miao Shuing-6 (100), elementary winding is connected directly crosses over incoming line and secondary winding is connected in series in the load-side that is connected in parallel of elementary winding.In the alternate embodiment of invention, secondary winding be connected in series to the line side and elementary winding be connected in load-side in parallel, be positioned at after the secondary winding.

Fig. 7 shows this connection of power controller 200, wherein identical among each label of winding and switch and Fig. 2.The operation class of power controller 200 is similar to the work of power controller 100, and identical switching causes aforesaid identical voltage.In some embodiment of invention, the controller 100 that controller 200 replaces among Fig. 1.

In some embodiment of invention, target is the voltage that mates when load is reduced in induction motor or other loads.For induction motor, for any specific mechanical load, the speed of rotation and the electric current that draws (current drawn) regulate automatically that they are own to meet mechanical load.When load was reduced, speed improved so that it more descends near synchronizing speed and electric current, and power factor and efficient also descend.In an embodiment of invention, regulate the voltage applied so that for this input voltage motor decide electric current near quota and power carries out work.

In another alternate embodiment of invention, a side of each elementary winding is connected to the line side of secondary winding and the opposite side of elementary winding is connected the load-side of secondary winding.

Fig. 8 shows this connection of power controller 300, wherein identical among each label of winding and switch and Fig. 2.The operation class of power controller 300 is similar to the work of power controller 100, and identical switching causes aforesaid identical voltage.In some embodiment of invention, the controller 100 that controller 300 replaces among Fig. 1.

Though the work of the embodiment of Fig. 7 and Fig. 8 is similar to the work of Fig. 2 substantially, voltage (and preferred transformation ratio) can be different a little, and this depends on the utilization of invention.For example, for the embodiment of Fig. 7, elementary winding is rated for 230V and secondary winding when being rated for 110V, for short circuit K1, and K3; Short circuit K1, K4; Short circuit K2, K3; And short circuit K2, K4 and K6 output voltage are respectively 220V, 250V, 300V and 400V.For example, for the embodiment of Fig. 8, elementary winding is rated for 280V and secondary winding when being rated for 120V, for short circuit K1, and K3; Short circuit K1, K4; Short circuit K2, K3; And short circuit K2, K4 and K6 output voltage are respectively 230V, 260V, 320V and 400V.Be stressed that, these three embodiment for all, the wide in range selection of primary/secondary ratio is available and can be conditioned to provide the various magnitudes of voltage of different brackets.

The adjusting of voltage can be in response to the phase place of the measurement of the RPM (revolutions per minute) of motor or electric current that draws or electric current and is carried out automatically.

With reference to Fig. 1, measurement module 108 is used for measuring one or more indicating devices of the loading of motor 102.This type of indicating device comprises the phase place of the electric current (relative voltage) that enters power of electric motor, is input to power of electric motor, the speed of rotation and the electric current of motor.Alternatively, can measure the electrical characteristic of motor in the upstream of power controller.

Each these indicating device can be used for understanding motor and whether operate in appropriate voltage at mechanical load, and whether perhaps be used for understanding the voltage that is transported to motor too high for the most effective work.

Especially, when being input to power of electric motor when being lower than given threshold value at any given input voltage, then supposition is that voltage can be reduced (following the increase of electric current) safely to supply with identical mechanical load.If the phase place of electric current greater than set-point, then can provide identical supposition than the phase lag of voltage.Similarly, the synchronizing speed with motor shows that near the rotary speed that surpasses certain value motor is underload for the input voltage of motor.

Under each situation in these situations, controller 106 determines that whether motor can carry required power and still be in the electric current restriction as the characteristic of motor with the available voltage of the next one.If motor can, then the voltage of being supplied with by power controller 100 is adjusted to next available low voltage.Similarly, controller 106 can determine that motor is near its peak power that can obtain based on the operating characteristic of being supplied with by measurement module 108 under the voltage that just is being supplied to.In this case, controller 106 can change switching mode in power controller 100,200 or 300 to supply with high voltage to motor.

Fig. 9 is the flow chart of the voltage of control of induction with the method for the load voltage on the coupling motor.702, determine motor characteristic.704, motor characteristic and standard compared be used to determine whether and improve or to reduce voltage, as mentioned above.If this voltage is " appropriate " voltage for load, then module 108 and controller 106 continue to monitor whether wish to change voltage.If it is diminishbb that voltage is confirmed as, then voltage is reduced 706.If determine that voltage should increase, then voltage is increased 708.In all cases, all to monitor this characteristic to determine whether voltage is fit to.

Alternatively, controller 106 contains relevant for the information of the operating characteristic of motor and with these characteristics and determines whether and will switch to the higher or low voltage of the next one to motor.

Should be appreciated that when actuating motor the measurement of motor operating characteristic can show that motor does not need the highest available voltage to supply with the required power of motor.In these cases, do not carry out one or more handover operations alternatively to high voltage.

Use power controller to reduce or control voltage to the motor supply though utilize above-described power controller 100,200 or 300 to explain based on the motor operating characteristic, other power controllers well known in the art can be used for this purpose.

It should also be understood that, though wish that in some embodiment of invention the monitoring motor characteristic is to determine when switched voltage, but this switching can be during starts the automatically performing of motor, and wherein this switches in after the previous switching or the special time after input current drops to the percentage that is lower than certain value or is lower than its initial value carries out.In this case, controller can be regarded as comprising timer or simple current measure device.

Understand that above-described method can change with many modes (comprise the order that changes step and/or carry out a plurality of steps simultaneously).Be to be further appreciated that the explanation of above-described method and apparatus will be interpreted into and comprise and be used to the method implementing the equipment of these methods and use these equipment.The present invention has described the detailed description of embodiment with nonrestrictive meaning, these embodiment be provide as example rather than to limit this scope of invention.Should be appreciated that about a described feature of embodiment and/or step and can use with other embodiment, and be not all embodiment of this invention all have shown in the certain figures or about described all features of one of embodiment and/or step.Those skilled in the art will expect the modification of described embodiment easily.And term " comprises ", " comprising ", " having " and their synonym thereof should mean " comprise but be not necessarily limited to " when using in the claims.

Notice that some embodiment among the above-described embodiment may describe the optimal mode that the inventor conceives, therefore can comprise the details of structure, action or structure and action, they may be dispensable but describe as example for invention.As known in the art, structure described herein and action can be substituted by the equivalent of carrying out identical function, even this structure or action are different.Therefore, this scope of invention only is subject to as employed element and qualification in the claim.

Claims (23)

1. equipment that is used to control the voltage of supplying with to load comprises:

Polyphase transformer, it has the primary and secondary winding that is used for every phase, each secondary winding be connected in series in incoming line and with output that this load is connected between; With

Elementary winding is configurable by switch, so that the phase place of the voltage of secondary winding and connected circuit differ one and be different from 0 degree and 180 phase places of spending.

2. equipment as claimed in claim 1, wherein said switch comprises:

A plurality of switches, it is switchable switching the input of each elementary winding, so that their carry out selectivity with in the various configurations that comprises at least a configuration more than one and connect, each elementary winding is connected at least a configuration:

(a) in the input that connects with its secondary winding mutually and between another input phase;

(b) in the input that connects with its secondary winding mutually and between neutral point or the dummy neutral;

(c) be different between the input two-phase mutually that connects with its secondary winding; With

(d) be different between the input phase and neutral point or dummy neutral mutually that connects with its secondary winding.

3. equipment as claimed in claim 2, wherein said a plurality of switches can also the elementary winding of (e) short circuit.

4. equipment as claimed in claim 3, wherein for (e), corresponding secondary winding is also by short circuit.

5. as each described equipment among the claim 2-4, wherein elementary winding and secondary winding are configured to make the voltage of output be lower than in (a) to (d) each line voltage.

6. as each described equipment among the claim 2-5, wherein said a plurality of switches are switchable switching the input of each elementary winding, thus they be connected by selectivity in (a) to (d) two or more multinomial between.

7. as each described equipment among the claim 2-6, wherein said a plurality of switches are switchable switching the input of each elementary winding, thus their alternatives be connected in (a) to (d) three or more multinomial between.

8. as each described equipment among the claim 2-7, wherein the switching of (a) to (d) is only carried out at the elementary winding of transformer.

9. as each described equipment among the claim 2-8, wherein, needn't switch in the circuit between input and load in (a) to (d), switching between the item arbitrarily.

10. each described equipment in the claim as described above, wherein with regard at least a configuration of these switches, the voltage of output is higher than line voltage.

11. each described equipment in the claim as described above, wherein these switches can be put upside down these at least a polarity in connecting.

12. each described equipment in the claim as described above, wherein polyphase transformer is a three-phase transformer, and wherein input is a three-phase voltage source.

Secondary winding is connected in series to and is positioned at the load-side that is connected in parallel on the circuit 13. each described equipment in the claim as described above, wherein elementary winding are connected directly the crossover track input.

14. as each described equipment among the claim 1-12, wherein the input of secondary winding and line is connected in series and elementary winding is connected in parallel to the circuit of the load-side that is positioned at secondary winding.

15. as each described equipment among the claim 1-12, wherein the input of secondary winding and line is connected in series, and a side of each elementary winding is connected the line side of secondary winding, the opposite side of elementary winding is connected the load-side of secondary winding.

16. a voltage method that changes to load comprises:

Control is as each described equipment among the claim 1-15 between heterogeneous input and load;

By with the corresponding different configurations of the different voltages of crossing over secondary winding between sequentially switch elementary winding, make output voltage change at least one level.

17. method as claimed in claim 16, wherein output voltage changes to high voltage step by step from low voltage.

18. method as claimed in claim 17, the characteristic of sensing lead wherein, and wherein when this characteristic reaches given standard, stop voltage and rise.

19. as each described method among the claim 16-18, wherein this load is an induction motor.

20. a voltage method that changes to induction motor comprises:

The equipment of the power that is used to be controlled to load is connected between input and the induction motor;

Under given voltage, measure the characteristic of this induction motor;

Based on this characteristic, determine that improving voltage still is reduction voltage; With

Determine in response to this, change output voltage.

21. method as claimed in claim 20, wherein said equipment are as each described equipment among the claim 1-15.

22. as each described method among the claim 16-21, wherein the mean-square value of input line voltage is greater than 270V.

23. as each described method among the claim 16-22, wherein this load is a threephase motor.

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