CN2255689Y - Emergency protection circuit device for electric motor - Google Patents

Abstract

The utility model relates to an emergency circuit protection circuit, particularly an emergency circuit protection circuit for motors. The utility model is characterized in that the control circuit of the common motor is connected with a plurality of thermistors in series; a plurality of thermistors are respectively arranged in the enamel-insulated wire winding of a stator. The utility model utilizes the working principle that the temperature of the utility model is risen with the winding coil in synchronism, the resistance value is enlarged, the current of the control circuit is reduced, the alternating current contactor is forced to automatically cut off, and then the utility model carries out the emergency protection on the motor. The utility model has the advantage of simple structure, reliable operation and low cost. The utility model has important economic significance on the protection of the common motors with poor operation condition and long continuous operation time of cement plants, fiber plate plants, etc.

Description

Motor emergency protective circuit device

The utility model relates to a kind of emergency protective circuit device, particularly a kind of motor emergency protective circuit device.

Existing common electric machine does not generally all have emergency protective device, but uses very extensive.This motor is in operation as the what it perceives as anomalous operation situation occurring, as unexpected overload etc., the stator winding is sharply generated heat, and temperature raises suddenly and causes the winding coil short circuit and burn out.Particularly condition of work is abominable, and the motor of long-time continuous running such as cement plant, fibre-board plant all has in a large number to burn out every year, causes the tremendous economic loss to enterprise.For understanding time this problem, prior art is that thermal relay or overcurrent, the phase failure, short-circuit protector are installed on the motor main circuit.But, the thermal relay poor sensitivity, reaction time is long, if when suddenly overload taking place in several seconds behind the motor normal starting, the stator winding coil temperature certainly will sharply raise, and the temperature rise of thermal element can not be synchronous in the thermal relay, temperature rise promptly occurring lags behind, this just can not in time disconnect control circuit, thereby has lost the protective effect to motor, and the result burns out motor probably; In addition, when being higher than the ambient temperature of thermal relay position as the location circumstances temperature of motor, the thermal element that continues in the device because of motor and heat has had a temperature difference, if overload during electric motor starting, will more be difficult to protect motor.If overcurrent, the phase failure, short-circuit protector are installed, then complex structure, element is many, cost is high, easily changes owing to various parameters simultaneously, also is difficult to protect effectively motor.

The purpose of this utility model is to provide a kind of simple in structure, with low cost and ten minutes motor reliable emergency protective circuit device of connecting three thermistors and constituting in control circuit.

The purpose of this utility model is achieved like this: three thermistors of series connection also are included in respectively in three enamelled wire windings of motor stator on the control circuit of motor; make thermistor directly respond to the working temperature of winding; in case being in operation, motor overloads; the temperature potential of winding must sharply raise; the temperature of thermistor also will sharply raise simultaneously this moment; resistance value increases thereupon; according to Ohm's law and series connection dividing potential drop theorem; the control circuit electric current descends; the contactor coil terminal voltage reduces; make the A.C. contactor automatic disconnection on the control circuit, main circuit dead electricity then, thus reach the purpose of protection motor.Unusual and when causing electric current excessive as the coil working of A.C. contactor; the temperature of thermistor will sharply raise; resistance also will increase simultaneously until reaching infinitely great, and this moment, it was equivalent to an insulator, so also can the automatic disconnection control circuit and motor is protected.The utility model is compared with the existing various protectors that are installed on the control circuit; its structure is very simple; cost reduces greatly; urgent protection to motor then can produce a kind of beyond thought effect; this is for the abominable factories (as cement plant, fibre-board plant) that must use common electric machines again in a large number of those machine operation environment; can protect a large amount of motors not burnt out, thereby make enterprise save substantial contribution, reduce cost, guarantee ordinary production and increase economic efficiency.

Accompanying drawing is a circuit working schematic diagram of the present utility model.

Now only three thermistors are described in detail with the structure that three enamelled wire windings combine according to accompanying drawing.

As shown in the figure: A.C. contactor [1], starting switch open in usual [2] and normally closed type shutdown switch [3] are arranged in the circuit for controlling motor [I], series connection three thermistors [7], [8], [9] on the circuit between starting switch and the shutdown switch, and be included in respectively in stator winding [4], [5], [6], but must be noted that with winding coil and insulate.According to the temperature limit of motor stator winding, the temperature of thermistor should be controlled at below 90 ℃, when reaching this temperature value, contactor [1] but just automatic disconnection.For 90 ℃ of the temperature limits of controlling thermistor, then Control current also should correspondingly be regulated and control in the 25mA-45mA scope, the method for its adjustment be when guaranteeing normal voltage A.C. contactor [1] can the prerequisite of adhesive under, suitably increase coil turn; Or the contact area of increase thermistor and motor windings.Like this; in stator enamelled wire winding [4], [5], [6] any one group; or two groups or three groups are because of the operation irregularity adstante febre; then can correspondingly there be one or two or three from winding, to absorb heat in thermistor [7], [8], [9]; its temperature can raise synchronously with the heating winding basically; when temperature reaches 90 ℃, because of increasing, resistance value makes [1] disconnection, main circuit [II] dead electricity in the control circuit, and motor quits work and is protected.

Claims (1)

1, a kind of motor emergency protective circuit device comprises circuit for controlling motor, it is characterized in that, three thermistors of series connection and being included in respectively in three enamelled wire windings of motor stator on the control circuit of TV, but with the magnet wire insulation of winding.

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