CN2293148Y - Multifunctional contactless protector for motor - Google Patents

Abstract

The protection system of the three-phase asynchronous motor has a plurality of defects so far, the fuse protector is unreliable in motor protection, the thermal relay, the air switch and the sensitivity are poor, the phenomenon of burning the motor can also occur in the use process, various motor protectors protect the motor by switching on and off contacts of the relay, and the contacts are easy to oxidize and corrode, after a period of time, contact flashover often occurs, so that the contacts are burnt or adhered, and the protection effect on the motor is lost. The multifunctional contactless protection device for the motor has the advantages of safety, reliability, high action speed, long service life and the like. As can be seen from the attached drawings, the fuse, the thermal relay and the air switch are all eliminated. The device uses an electronic switch element to be connected in series with a motor control loop to achieve the effect of protecting the motor. The electronic switching element is controlled by the bistable circuit. When the motor works normally Q₁On, Q₂Is at the cutoff. When phase loss or phase voltage serious unbalance (more than or equal to 20 percent) occurs and overcurrent occurs, the bistable circuit is overturned to ensure that Q is ensured₂On, Q₁And the motor can be protected from being burnt out by cutting off.

Description

The multi-functional contactless protective device of motor

The present invention relates to threephase asynchronous because of phase shortage or press serious uneven (〉=20%), overload etc. mutually, can prevent the protective device that is not burnt.

During the threephase asynchronous operation; because protection system is deposited so far also in a lot of weak points; the most fuses that use of the following motor of 40KW; motor is because of the earlier disconnected phase of the most fuses of certain reason (certain phase ground connection or phase fault etc.) in actual application; just cause phase-deficient operation; make burn-down of electric motor; heavy-duty motor all is that application thermal relay and air switch are used the protection motor; but because mechanically operated relation; sensitivity is very poor; when over current of motor, also the burn-down of electric motor phenomenon can often take place.Therefore people develop multiple motor protecter again, but all are by the through and off in motor control loop of relay contact string, and motor has been played the certain protection effect.But the easy oxidation in contact, corrosion etc. can cause poor contact of contacts, arcing, are directed at that burn the contact or adhesion, have just lost the protective effect to motor.Therefore China will have hundreds of thousands platform motor to be burnt every year, causes enormous economic loss to country.For overcoming above-mentioned shortcoming; the multi-functional contactless protective device of a kind of motor is proposed; it have safety, reliable, noiseless, power consumption less, advantage such as the life-span is long, easy for installation, use this device and can cancel fuse, thermal relay, air switch, guarantee that motor safety turns round.

For finishing above-mentioned task, the present invention proposes following scheme:

Promptly between phase line and phase line or phase line and zero line, by fuse, normally closed button, often drive button, A.C. contactor, be unified into motor control loop successively, a kind of electronic switching element of series connection in this loop, be these element through and off, be provided with and a kind ofly be subjected to phase shortage or press serious imbalance and overload control circuit mutually, said switch element is elements such as bidirectional triode thyristor or solid-state relay.

Said control circuit comprises:

1. bistable circuit; 2. phase shortage or press serious uneven testing circuit mutually; 3. motor overload testing circuit; 4. power circuit.

Said bistable circuit is by transistor (Q _1-2), load resistance (R ₂, R ₃, R ₆) inter-stage coupling resistance (R _4-5), be worth resistance (R partially _7-8), speed-up capacitor (C _2-3) form.

Said motor overload testing circuit is by three (L _1-3) have a coil of magnet ring, rectification diode (D _1-6), load resistance (R ₁), filter capacitor (C ₁) get control voltage potentiometer (W), the motor divider resistance of different capabilities (perhaps according to), voltage-stabiliser tube (DZ ₁) form.

Said motor phase shortage and press serious uneven testing circuit mutually is by three high resistant electric capacity (C _8-10), transformer (T ₁), rectifier diode (D ₁₂), current-limiting resistance (R _10-11), voltage-stabiliser tube (DZ ₃), electric capacity (C _6-7) form.

Said power circuit is by transformer (T ₂), rectifier diode (D _8-11), divider resistance (R _9-10), supply with the positive and negative DC power supply of bistable circuit, filter capacitor (C _4-5) form.

From schematic diagram as can be seen, when knife switch (K) when closing, press starting button (SB ₁), A.C. contactor (KM) action, the adhesive of KM contact, motor runs well, this moment the bistable circuit operate as normal because R ₇And R ₈Resistance difference (R ₇＞R ₈), so Q ₁And Q ₂Added inclined to one side value is unequal on two transistor bases, so behind the power connection, Q ₁Elder generation's conducting, Q ₂Be in cut-off state, switch element (BT) meanwhile is because of there being the trigger voltage normally.Then decontrol button (SB ₁) time, A.C. contactor is operate as normal still, has guaranteed the motor normal operation.

1. motor phase shortage or press serious uneven testing circuit mutually is when phase shortage not or differ less than 20% the time transformer (T ₁) former limit (being that N point center line is between zero point) have a spot of electric current to flow through, because transformation ratio is big, thus induced voltage that the limit produced paid less than 2 volts, and Q ₂Base stage is in positive 2 volts of voltages, so bistable circuit still keeps original operating state.Loosening or connect bad and outside line is fallen to cause mutually motor power phase shortage to occur or pressed serious uneven (〉=20%), T mutually when the motor three-phase power junction ₁Its pair limit just has greater than the output of 3 volts induced voltage, through D with regard to higher input voltage is arranged on former limit ₁₂Rectification, C ₆Filtering, R ₁₁And DZ ₃Amplitude limit passes through R ₁₀, D ₇Add to Q ₂Penetrate between base stage, polarity H point is that positive G point is negative, is Q thereby make the bistable circuit upset ₂Conducting, Q ₁End, this has just cut off trigger voltage, bidirectional triode thyristor is disconnected, thereby A.C. contactor (KM) quits work.Just broken this moment whole power supplys of motor have protected motor not burnt capacitor C ₇Be to prevent to disturb and the misoperation (being 0.47 microfarad) that causes.

2. overload protection, from overload detection circuit as can be known; The three phase mains of motor (A, B, C) passes three coil (L that have magnet ring respectively _1-3), when machine operation, induced voltage output is just arranged, through diode (D _1-6) bridge rectifier, through electric capacity (C ₁) be added on potentiometer (W) two ends after the filtering, to surpass permission straight when current of electric, makes voltage-stabiliser tube (DZ ₁) be in not breakdown conditions, keep the former operating state of bistable circuit.(before motor is not worked, earlier potentiometer (W) E point and F point are transferred to coincidence, when machine operation,, adjust the position that potentiometer (W) E is ordered, make the voltage (measuring E, P 2 points) at voltage-stabiliser tube two ends be less than DZ with table according to the motor of different capacity ₁Puncture voltage should be according to the real work electric current of different motors and the difference size of rated current less than what, determines the position that E is ordered, and just how many volts are the voltage-stabiliser tube both end voltage should be transferred to, and (are less than voltage-stabiliser tube DZ certainly ₁Puncture voltage (less than 4 volts), also can be, determine the position that good E is ordered earlier with divider resistance according to the rated value of different current of electric).Because of in a single day certain reason is transshipped, the main circuit current certificate increases, so voltage rises between DF, thereby EF voltage is along with increasing, and is added in voltage-stabiliser tube (DZ ₁) voltage at two ends is voltage sums between voltage and GP between EF, because of voltage between EF raises, certainly will cause voltage-stabiliser tube (DZ ₁) puncture, at this moment DZ ₁It is about 4 volts that both end voltage remains puncture voltage, and between EF voltage greater than voltage-stabiliser tube (DZ ₁) puncture voltage, so the voltage that F point (also being the G point) is ordered to P just is converted into negative value, this just makes Q ₂Conducting, bistable circuit upset, Q ₁End, just cut off the silicon controlled trigger voltage simultaneously, controllable silicon is disconnected, and A.C. contactor quits work simultaneously, has also just cut off the three phase mains of motor, reaches the purpose that the protection motor is not burnt because of overcurrent.Resistance R ₁₀Effect have two: the one, during operate as normal, guaranteed that S point electrical potential energy at positive about 2 volts, makes Q ₂By better, in order to avoid misoperation, because bistable circuit (4 volts) power supply R that flows through just ₇To S point back minute two-way, the one tunnel through voltage-stabiliser tube (DZ ₃) and R ₁₀To zero point, and circulate another Lu Zejing FE and voltage-stabiliser tube (DZ ₁), (this fashion does not puncture has only very little leakage current, so equivalent resistance is very big) is to zero point, again because DZ ₃It is very little to be in the step-down of forward conduction state, so will add R ₁₀, R ₁₀Another effect is when high voltage output is arranged between HG, restriction Q ₂Base current so as not to pipe burnt out.

Major function of the present invention: 1. open phase protection; 2. three-phase voltage serious uneven (greater than 20%) protection; 3. motor overload protection; 4. motor is swept the boring protection; 5. short-circuit protection between winding; 6. certain phase voltage ground protection; 7. being applied in ac contactor coil voltage is 380 volts and 220 volts two kinds; 8. the control power of motor is 3KW～320KW; 9. the application of motor three-phase mains voltage is 380 volts and 660 volts two kinds.

Claims (3)

1, a kind of being located between phase line and phase line or phase line and the zero line is by fuse (FU), A.C. contactor (KM), normally closed button (SB ₂), often open button (SB ₁) be unified into motor control loop, it is characterized in that a kind of electronic switching element of series connection in the control loop, be the crux spare of the multi-functional contactless protective device of motor, and this element is controlled by bistable circuit, because two diode (Q of bistable circuit ₁And Q ₂) only there is a pipe conducting, the feature that the another pipe ends is controlled the electronic switching element through and off, reaches the effect of protection motor.

2, according to multi-functional its feature of contactless protective device of right 1 described motor, be said electronic switching element, be bidirectional triode thyristor or solid-state relay.

3, require the multi-functional contactless protective device of said motor to comprise according to right 1:

(1). bistable circuit is by triode (Q _1-2), load resistance (R ₂, R ₃, R ₆), inter-stage coupling resistance (R _4-5), be worth resistance (R partially _7-8), speed-up capacitor (C _2-3) form.Because of R ₇＞R ₈, Q during the motor operate as normal ₁Conducting Q ₂End;

(2). phase shortage or press serious uneven testing circuit mutually, by three high resistant electric capacity (C _7-9), transformer (T ₁), diode (D ₁₂), current-limiting resistance (R _10-11), voltage-stabiliser tube (DZ ₃), filter capacitor (C ₆), prevent interference capacitors (C ₇) form, work as three-phase voltage, phase shortage takes place or press seriously when uneven mutually, this circuit just has output voltage to be added in Q ₂Penetrate on the base stage, need only when detecting voltage Q greater than 3 volts ₂Base stage becomes negative potential, Q ₂Conducting makes bistable circuit upset Q ₁End, this The Trigger of Bidirectional Triode Thyristor voltage that just falls to have broken quits work A.C. contactor and has just protected motor not burnt;

(3). cross and cut testing circuit, by coil (L _1-3), rectification two utmost point (D _1-6), filter capacitor (C ₁), current-limiting resistance (R ₁), potentiometer (W), voltage-stabiliser tube (DZ ₁) form; During the motor operate as normal, voltage-stabiliser tube (DZ ₁) do not puncture, being transferred to by potentiometer (W) is that E, P two point voltages are less than voltage-stabiliser tube (DZ ₁) puncture voltage, electric current is added in voltage-stabiliser tube (DZ this moment according to increasing when overload ₁) voltage increases at two ends, make voltage-stabiliser tube (DZ ₁) puncture, G by just being converted into negative value, makes the bistable circuit upset, Q to the P point ₂Conducting, Q ₁End, this moment, the bidirectional triode thyristor trigger voltage was cut off, and A.C. contactor (KM) is quit work, and the three phase mains of the motor that also just broken has protected motor not burnt.

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