CN1039564C - Controllable current starter for winding-type motor - Google Patents

Abstract

When the general winding type AC motor is started, a motor rotor is connected with a resistor or a reactor in series. The starting torque is reduced, the brake current is enlarged, and the use rate of the motor is reduced. The rotor is connected with a group of resistors controlled by an antiparallel thyristor, and a thyristor trigger detects the frequency of rotor voltage. During start, the half-cycle time t<2> of the rotor voltage is measured. According to the operation characteristic of the motor, the delaying triggering time t<2>' of the thyristor is adjusted. The starting process of the motor is controlled by the conducting time t<2>'=t<2>-t<2>' of the thyristor. After the starting control device and a method are adopted, the motor has the advantages of good starting characteristics, great large torque and high motor efficiency.

Description

Controllable current starter for winding-type motor

The invention belongs to electric motors, particularly controllable current starter for winding-type motor.

During conventional wound type AC motor starting, rotor must seal in additional resistance or reactance, with the mean value of restriction starting current, makes it to be no more than 2 times of rated current of each duty.A large amount of equipment that repeat short time duty that use in the smelter, these equipment great majority adopt the starting of winding-type motor rotor serial connection frequency sensitive varistor.The actual conditions that repeat the motor work of short-term operation are in transition operation such basically, the working speed of motor is different because of the operating characteristic of manufacturing machine, the higher motor speed of the frequent degree of repetitive operation is lower, and then working speed is higher for the lower motor of the frequent degree of repetitive operation.Common motor maximum speed is about 70～80% of a rated speed.Practice shows, behind the motor rotor serial connection frequency sensitive varistor, power factor during motor starting is less than 0.5, the motor starting torque is about 1.2 times of nominal torque, rotor current is about 2.5 times of rated current, needs to draw from electrical network very most of reactive current in the motor starting procedure.Because the rotor starting electric current is big, often causes the slip ring and the winding scaling loss of motor, and need electrical network is carried out idle capacitance compensation.But after additional resistance or reactance, the starting characteristic deliquescing of motor, or starting torque diminishes, and the motor utilance is descended.Be that starting characteristic is soft behind the motor rotor series resistor; Starting torque diminishes behind the string frequency sensitive trheostat, and stalling current is big, and the motor utilance reduces.

European patent EP 0446936A2 discloses a kind of motor controller with bypass contactor, is made up of three groups of three groups of inverse parallel controllable silicons that are connected on the stator three-phase, and adopts microcomputer and a bypass contactor to realize start-up control.U.S. Pat 4100469 disclosed mixed type motor starters are formed by being connected on the stator three groups of inverse parallel controllable silicons and corresponding contactor and an acceleration control circuit, solid-state control is subjected to quicken the control motorized motions, acceleration motor in start-up course, when reaching synchronizing speed, the operation contactor gets electric, its junction closure.Connect motor current, therefore when steady operation, solid-state control is a bypass.Utility model patent CN2121771U and patent of invention CN1055845A disclose AC asynchronous motor starting energy-saving appliance and modulating speed control startup method respectively.All these technology all are connected with the motor stator winding and realize controlling, and structure more complicated all.

The objective of the invention is to reach the restrictions motor starting current, to improve the purpose of motor torque and motor utilance by controlling the size of motor rotor electric current by thyristor controlled resistance normal connecting resistance of rotor serial connection and one.

According to the present invention, controllable current starter for winding-type motor is by being made up of with another controlling resistance that becomes with controllable silicon parallel resistor serial or parallel connection and relevant silicon controlled toggle a resistor of being connected in series mutually with motor rotor.Two antiparallel controllable silicons be in parallel or connect with another resistor again after a resistor is connected, again this serial or parallel connection resistance is connected in series mutually with motor rotor, each of rotor all is connected in series such one group of string (also) connection resistance mutually, and a silicon controlled toggle is connected with each group inverse parallel controllable silicon respectively.

According to the present invention, detect the motor rotor electric voltage frequency by silicon controlled toggle, automatically follow the rotor voltage and the frequency of variation as synchronizing voltage with the rotor voltage frequency, the control silicon controlled angle of flow, utilize the current compensation rotor current of controllable silicon through resistor, improve the motor starting torque, reach desirable motor starting characteristic.

Because being the operating characteristic with motor, the frequency of motor rotor voltage changes, when motor speed approaches zero, and frequency f ₂≈ 50Hz; When rotating speed approaches synchronous speed, frequency f ₂≈ 0; When the motor plug braking, 50Hz＜f＜100Hz.

The used time of the every half period of motor rotor alternating voltage of working when different frequency is

t ₂=1/2f ₂In the formula, t ₂: the time that the alternating voltage half period is used;

f ₂: the motor rotor frequency.

T delays time after silicon controlled toggle detects motor rotor voltage ₂Controllable silicon is triggered in ' back, makes it conducting.The silicon controlled trigger angle is to be subjected to rotor voltage every half period time t in starting process ₂Controlled.And time-delay triggered time t ₂' then be to adjust according to the required operating characteristic of motor.Adjust time-delay triggered time t ₂' after, silicon controlled ON time t ₂" also determined by following formula:

t ₂″＝t ₂-t ₂′

Be controllable silicon ON time t ₂" equal rotor alternating voltage half period time t ₂Deduct time-delay triggered time t ₂'.The silicon controlled pilot angle is determined by following formula:

α ₂"=(f ₂/ 50) α ₂In ' the formula, α ₂": the SCR control angle in the motor starting procedure;

α ₂': silicon controlled pilot angle when frequency is 50Hz.Because α ₂'=t ₂'/0.01 * 180=18000t ₂'

α ₂″＝360f ₂·t ₂′。

Only at rotor voltage half period time t ₂Greater than time-delay triggered time t ₂In ' time, silicon controlled toggle is just exported trigger impulse, therefore, and when the motor plug braking, just at 50Hz＜f ₂During＜100Hz, controllable silicon is in off state.

Result of the test shows, compared with prior art, utilize controllable current starter for winding-type motor of the present invention, power factor during motor starting is brought up to more than 0.98 from about 0.5, the motor starting torque still is about 1.2 times of nominal torque, the motor rotor starting current drops to about 1.2 times from about 2.5 times of rated current, only needs to draw from electrical network seldom a part of reactive current in the motor starting procedure.Motor starting is to 80% of rated speed, the average power factor improves more than 40%, and mean starting current descends more than 40%, and the electric motor overheating amount reduces more than 60%, thereby prolonged the useful life of motor, and need not electrical network is carried out idle capacitance compensation.

The invention will be further described below in conjunction with accompanying drawing.

Fig. 1 is a motor rotor control circuit of the present invention.

Fig. 2 is the silicon controlled toggle schematic diagram.

Fig. 3 is the motor starting characteristic curve.

Fig. 4～Fig. 6 is the various mode of connections on Shen motor rotor control Shen road.

As shown in Figure 1, winding-type motor controllable silicon starting device of the present invention is by three groups on the rotor that is concatenated into motor D three phase a, b, the c conventional series resistor R_a、R _b、R _cThyristor controlled resistance and silicon controlled toggle (Fig. 2) form, and SCR control resistance is by two antiparallel controllable silicons and the resistance R that is in series with it_a1、R _b1、R _c1Organize Become. Normal connecting resistance R_a、R _b，R _cRespectively with inverse parallel controllable silicon and resistance R thereof_a1、R _b1、R _c1Be in parallel, these three groups of controlling resistances are star-connection.

The input of silicon controlled toggle T joins with three-phase a, b, the c of motor rotor respectively, output respectively with inverse parallel silicon controlled control utmost point G_aZ、G _aF、G _DZ、G _DF、G _bZ、 G _bF, negative electrode a₁、a，b ₁、b，c ₁, c is connected.

Motor D rotates, and silicon controlled toggle T detects the electric voltage frequency of motor D rotor each phase a, b, c, adjusts time-delay triggered time t according to the needed operating characteristic of motor₂', the ON time t of controllable silicon in the different frequency situation₂″＝t ₂-t ₂'. Utilize Controllable silicon improves the starting torque of motor through the current compensation rotor current of resistor, Improve electronic starting characteristic.

Fig. 3 has compared only with conventional series resistor R_a、R _b，R _cThe time the motor starting spy Motor starting characteristic curve II behind linearity curve I and the use starting device of the present invention. Can obviously find out from Fig. 3, adopt controllable silicon starting device of the present invention after, starting characteristic Firmly, starting torque increases, thereby has improved the motor utilization rate.

Fig. 4～Fig. 6 is other several embodiments of the present invention.

In control circuit shown in Figure 4, it connects method is with three groups of inverse parallel controllable silicons and resistance R_a1、R _b1、R _c1After the parallel connection again with conventional series resistor R_a、R _b，R _cBe in series. Its Surplus method of attachment is identical with embodiment shown in Figure 1.

In scheme shown in Figure 5, three groups of conventional resistance of SCR control resistance are the angle type Connect, all the other mode of connections are identical with scheme shown in Figure 1.

In scheme shown in Figure 6, three groups of conventional resistance of SCR control resistance are the angle type Wiring, all the other mode of connections are identical with scheme shown in Figure 4.

All these schemes can both obtain same effect.

Embodiment.

The controllable silicon starting device that is used for YZR225 * *-2 22kW motor.

Motor load torque M ₂=0.8Me

Load factor FC=40%;

Number of starts: 300 times/h,

Rotor current I _2*=45.6A;

Rotor open circuit voltage U ₂=234v

Normal connecting resistance R _a=R _b=R _c=1.4 Ω, controllable resistor R _A1=R _B1=R _C1=0.8 Ω triggers electrical equipment delay time t ₂'=0.01s.

Table 1 has been listed the value of each parameter in the starting process, and its characteristic curve as shown in Figure 3.Curve I is that motor only is connected in series a normal connecting resistance R ₂Characteristic curve during=1 Ω, starting current at this moment The starting torque of curve II is big, and starting characteristic is hard, and the utilance of motor can be high more than 30%.

In the table, S=f ₂/ 50 $I_2=S{U}_2/\sqrt{3}{R}_2$ ${I_2}^{\&prime;}=S{U}_2/\sqrt{3}{R_2}^{\&prime;}\sqrt{\frac{1}{2\mathrm{\&pi;}}\sin 2\mathrm{\&alpha;}+\frac{\mathrm{\&pi;}-\mathrm{\&alpha;}}{\mathrm{\&pi;}}}$

I＝I ₂+I ₂′

Table 1

Claims (6)

1, a kind of normal connecting resistance and three groups of inverse parallel silicon controlled winding-type motor controllable silicon starting devices of utilizing, it is characterized in that this device is made up of three groups of thyristor controlled resistance of inverse parallel and silicon controlled toggle T, said thyristor controlled resistance is connected in the motor rotor loop and by two antiparallel controllable silicons be attached thereto the controlling resistance R that connects _A1, R _B1, R _C1Form said normal connecting resistance R _a, R _b, R _cRespectively with inverse parallel controllable silicon and resistance R thereof _A1, R _B1, R _C1Be connected, these three groups of controlling resistances interconnect, and the input of said silicon controlled toggle joins with three-phase a, b, the c of motor rotor respectively, its output respectively with inverse parallel silicon controlled control utmost point G _AZ, G _AF, G _DZ, G _DF, G _CZ, G _CFWith negative electrode a ₁, a, b ₁, b, c ₁, c is connected.

2, according to the winding-type motor controllable silicon starting device of claim 1, it is characterized in that respectively organizing inverse parallel controllable silicon and controlling resistance R _A1, R _B1, R _C1Be in series.

3, according to the winding-type motor controllable silicon starting device of claim 1, it is characterized in that respectively organizing inverse parallel controllable silicon and controlling resistance R _A1, R _B1, R _C1Be in parallel.

4,, it is characterized in that by each SCR control circuit of going up mutually is star-like wiring at motor rotor according to the electronic controllable silicon starting device of the winding-type of claim 1.

5, according to the winding-type motor controllable silicon starting device of claim 1, it is characterized in that being connected on each SCR control circuit of going up mutually of motor rotor is angle-type scheme.

6, a kind of winding-type motor method for starting-controlling that adopts the controllable silicon starting device is characterized in that:

(1) detect the frequency of motor rotor voltage by silicon controlled toggle T,

(2) utilize the motor rotor electric voltage frequency to control thyristor operating angle automatically as trigger synchronizing voltage and control voltage,

(3) adjust silicon controlled time-delay triggered time t ' according to the needed operating characteristic of motor ₂,

(4) get the ON time t of controllable silicon under the different frequency situation ₂" equal the half period time t of rotor voltage in starting process ₂Deduct controllable silicon delay time t ' ₂,

(5) determine silicon controlled pilot angle α by silicon controlled toggle T ₂"=360f ₂T ₂

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