DE3034904A1 - Electric motor low windings resistance protection system - compares windings resistance when motor is at rest with threshold value - Google Patents

Abstract

The protection system uses a sensor (20) for coupling to at least one motor winding and comparing the windings resistance when the motor is at rest with a threshold value, to provide a display signal when the threshold value is exceeded. An interrupter (RLS1) uncouples the motor winding from the sensor (20) when the respective motor winding is supplied with high voltages during operation of the motor, to prevent the sensor (20) being damaged. Pref. the sensor (20) comprises an operational amplifier supplied by the control current received from the starter for the motor via a rectifier bridge (12). The interrupter (RLS1) is operated by a relay coil coupled to the starter. The system is single and compact and easy to install.

Description

DESCRIPTION

The invention relates to a safety sensor device for use in electric motors, specifically the invention relates to a low-winding resistance protection system, in particular a device for determining the engine status or the engine states when the engine is at rest.

There are many types of safety sensor devices for engines known from the patent literature and commercially available.

The vast majority of these safety sensor devices determines engine properties and conditions while the engine is running. However a protective device that only works while the engine is running can be included Do not prevent the motor from burning out that occurs when the motor is initially put on or off.

at the beginning of the application of electrical current or electrical power occurs on the motor windings. Such burnout is due to degradation the insulation resistance caused by condensation and pollution will.

The frequency of such phenomena is a function of the relative Humidity, the concentration of airborne particles and of Changes in temperature in the environment in which the engine is operated. It is It is easy to see that polluted or harsh environments protect the engine against a reduction in the insulation, which can lead to the motor burning out during Leaving the same leads may require.

There are already protective devices for use with electric motors have been proposed which monitor the winding resistance in the idle state. In US Pat. No. 3,656,136 there is an electric motor with a safety sensor device shown. Here a small current is sent to a winding of a motor laid out, and the current level is monitored. If it gets too high, that's one indicates a low leakage resistance value to ground, an alarm indication is generated, and a relay that prevents the motor from being switched on is activated.

Another type of protection device is in U.S. Patent 3 611 036. Here are two motor connections through diodes that are in series are switched with neon lamps and current limiting resistors, with two input power lines tied together. A ground connection in the motor creates a flow of current through one or both of them Lamps. A photosensitive resistor activates in response to light from the lamps a relay control circuit, which opens the input line to the motor, so that the motor cannot be switched on.

The present invention provides a low winding resistance protection system for electric motors made available, which is characterized by small dimensions, simple and easy installation as well as reliable and reliable textures or properties that can damage the same due to high voltages, which are used to operate the engine, prevented.

In accordance with one embodiment of the invention, there is provided a low winding resistance protection system provided for electric motors, comprising a sensor device which is coupled to at least one motor winding and the winding resistance of the Motor, when it is at rest, compares it with a predetermined threshold value and an output indication signal in response to exceeding that threshold outputs, and a decoupling device for decoupling the at least one motor winding from the sensor device so that high voltages generated during operation of the motor are in contact with it, must be kept away from the sensor device.

Furthermore, the sensor device comprises according to one embodiment of the invention an operational amplifier.

Additionally, the system is in accordance with an embodiment of the invention designed to monitor an AC motor, and the decoupling device includes a relay, the view of the determined connection of an electric motor, by the circuit or the circuit between the at least one winding and the sensor device opens.

In addition, according to one embodiment of the invention a protection system is made available, which is particularly suitable for use with high-voltage electric motors, which are operated with 2000 volts and more is designed.

According to an alternative embodiment of the invention, the system is designed to monitor a DC motor, and the decoupling device includes a diode.

In addition, according to one embodiment of the invention, the is designed to monitor a DC motor, the sensor device current from a battery or the sensor device is powered by a battery provided.

Finally, according to one embodiment of the invention, in which the sensor device from a motor starter operated with high voltage Power is supplied, a device for decoupling the sensor device from the Engine starter power source provided during engine operation.

The invention is based on some in Figures 1 to 6 of the drawing, particularly preferred embodiments shown in principle explained in more detail; show it: Figure 1 is a schematic representation the electrical connections between a protection system according to the present invention Invention and a motor and a motor starter; Figure 2 is a schematic electrical Circuit diagram of a sensor circuit for an AC motor, which is part of a Protection system according to the present invention; Figure 3 is a schematic electrical circuit diagram of a sensor circuit for a direct current motor, the one Forms part of a protection system according to the present invention; Figure 4 is a schematic electrical circuit diagram of a sensor circuit for a direct current motor, the one Til a protection system according to the present invention; Figures 5A and 5B two perspective illustrations of part of a protection system according to FIG present invention; and FIG. 6 is a schematic electrical circuit diagram of a Sensor circuit that is particularly suitable for a high-voltage AC motor and forms part of a protection system according to the present invention.

Reference is now made to Figures 1 and 2, each of which Connections between the protection system according to the present invention and a Motor and a motor starter on the one hand and the sensor circuit, which is a part of the protection system, on the other hand, illustrate.

For the purpose of simplifying the explanation, the various Connections with numbered ports are identified, all of which are shown Embodiments of the invention are common. The special numbering sequence Has no meaning at all, and it can alternatively be any other Numbering system or any other numbering arrangement of the connections applied will.

The connections 1 and 2 are coupled to an electrical power source 10, typically or preferably to the control current, which over the contact coils any conventional motor starter, which in connection with an electric motor is used. The control voltage applied to connections 1 and 2 can be iryendeine suitable voltage, such as 110 to 440 volts. The connections 1 and 2 are coupled to the primary winding of a transformer TR 1. The secondary windings of the transformer TR 1 are coupled to a rectifier 12, the output of which provides a 12 volt DC power source for the remainder of the protection system.

Generally speaking, the protection system is to be understood as such, the one means for measuring the resistance between a winding of a to monitoring electric motor 14 and ground includes. In the preferred one considered here Embodiment, the electric motor 14 is a three-phase motor that has windings, identified by the letters U, V and W and those identified by the respective Phase connections are connected, identified by the letters R, S and T. will. The invention is not necessarily limited to three-phase motors, but it can be applied to any type of electric motor if appropriate.

Because the different windings U, V and W are electrically connected to each other are connected, the resistance measurement can be through a connection of any or several of the windings are effected.

In the present preferred embodiment, port is 3 coupled to winding U and terminal 6 to ground.

An operational amplifier 20, more typically or preferably a model CA 3094E from RCA Corporation serves as a comparator to compare the resistance of the winding to ground with a predetermined resistance threshold. The input terminal 2 of the amplifier is controlled via a resistor R 4 and a relay Switch RLS 1 coupled to terminal 3, which is connected to a motor winding is as mentioned above. The negative input terminal 3 is through a resistor R 6 coupled to a connection point 22. The junction 22 is over a resistor R 9 coupled to ground.

A connection point 24 which is connected to one output terminal of the rectifier 12 is coupled to the second output terminal via a capacitor C 1 of the rectifier and also via a resistor R 1 with a Sammelleit.ng 26 connected. A Zener diode D 4 is connected between ground and the bus 26. The junction between the capacitor C 1 and the second output terminal of the rectifier is also connected to ground. A resistor R 3 connects the Bus 26 with the junction between resistor R 4 and the switch RLS 1, and a capacitor C 2 connects the bus 26 to the input terminal 2 of the operational amplifier. The collecting line 26 is directly connected to the connection 7 of the operational amplifier 20 and via a resistor R 5 to the terminal 5 of the Operational amplifier 20 connected.

The manifold 26 is connected to the junction 22 via a resistor R 2 connected, the resistance of which corresponds to the leakage resistance threshold of the protection system certainly. The following table gives a list of resistance values for R 2 in kOhm and from the corresponding leakage resistance threshold values (kOhm) between the connection 3 and ground (the term "leakage resistance" is abbreviated here for "derivation resp.

Leak resistance used): Leakage resistance value R 2 1010 91 800 120 650 150 500 200 285 360 210 510 It should be noted that the above values are only given as examples for the special one shown in FIG Circuit are. Corresponding relationships of values for other specific embodiments can easily be determined using conventional empirical techniques.

The connection point 24 is via a light emitting diode D 2 in series with a parallel combination of a diode D 3 and a relay RL 2 connected to the terminal 8 of the operational amplifier 20. Terminal 4 of the operational amplifier is connected to ground, and its connection 6 is connected to ground via a resistor R 8 and connected to terminal 3 of the amplifier via a resistor R 7.

It is a special feature of the present invention that they can be easily connected to conventional motor starters and uses operating elements, which are conventionally provided therein so that in this way the duplication is switched off by switches and other components. An excitation coil 30 that forms part of the engine starter, actuates a switch 32 which is used to the connection between a three-phase power supply network at the terminals R, S and T and the respective motor windings U, V and W to control and that as well forms part of the engine starter. The spool 30 is conventionally over series-connected start, stop and overload switch 31 or 33 or 35 of the Power source 10 energized.

It is a special feature of the invention that in series connection from the power source 10 to the coil 30, the switch RLS 2 is provided, a series switch between the terminals 7 and 8, a control of the coil 30 and an actuation of the switch 32 in response to the winding resistance determined by the sensor enables.

It is also a special feature of the invention that the connections 4 and 5 are connected to the ends of the coil 30.

A diode D 4, resistors R 10 and R 11 and a relay RL 1, the the switch RLS 1 is operated, are connected in series between the connections 4 and 5, so that thereby an actuation of the switch RLS 1 in response to the sensor determined excitation of the motor is achieved.

According to an alternative embodiment of the invention, the switch RLS 2 omitted, and due to the low resistance determined by the sensors Windings will only be a sensitive indication, such as by lighting up the light-emitting diode D 2, made without a connection or excitation of the motor is prevented.

Typical component values with which particularly good operation of the device described above can be achieved are given below as preferred example values: D 1 Z 12 IN 4742 R 1 220 Ohm D 2 LED LSM-LA R 3 R4 D 3 IN 4004 R 7 D 4 IN 4007 R 9 all 470 KOhm rectifier 12 WO 2 GI R 8 51 Ohm C 1 100 F / 25 VR 5 + R 2 C 2 0.22 F / 100 VR 6 33 KOhm RL 1 RS 75001 (Kaco - Germany) RL 2 FTA 0012405 ( Feme - Italy) The values of R 10 and R 11 depend on the input voltage coming from the power source 10. If the input voltage is 110 VAC then both resistors are omitted. If the input voltage is 220 VAC, then R 10 27 is KOhin1 and R 11 is omitted. If the input voltage is 440 VAC, R 10 is 27 K ohms and R 11 is also 27 K ohms.

According to one embodiment of the invention, the connections 10 and 11 to an external recording device, to control devices or Alarm devices are coupled. In such a case, one of these can Connections can be coupled to the junction 24, or these two can be Connections can be coupled to the connection point 24.

The operation of the protective device described above is now briefly summarized. While the electric motor that is being monitored is in Is idle, the resistance between its windings and ground becomes continuous compared with a reference value previously determined by the value, which the resistor R 2 has received. If the measured resistance value falls below the Reference value falls, then the light emitting diode D 2 is actuated, and the relay RL 2 decouples the connections 7 and 8, so that the coil 30 is de-energized in this way and the engine breaker switch 32 is opened, thereby stopping the engine from operating is made impossible.

The motor can only be operated if the relay RL 2 and the Switch RLS 2 are de-energized, i.e. when the winding resistance rises to the above predetermined Threshold value returns.

On the other hand, the operation of the motor creates a voltage in the Induced coil 30, which causes actuation of the relay RL 1, which the switch RLS 1 opens and the high voltage applied to the motor windings from the Protective circuit is disconnected as long as the motor is switched on. This decoupling serves to prevent operation of the sensor circuit, and it from possible damage caused by the applied high voltage could be to protect.

Reference is now made to FIG. 3, which shows a sensor circuit for Monitoring a DC motor shows. The sensor circuit is pretty much the same with the sensor circuit illustrated here in FIG. For the sake of simplicity For explanation, the connection numbers are used here as well, which were used in the description Figures 1 and 2 were used.

Moreover, there are only parts of the circuit that differ from those differ from Figure 2, described in more detail below. the The rest of the circuit is the same as in the exemplary embodiment in FIG. 2.

Connections 1 and 2 are directly connected to the input connections of the Rectifier 12 instead of running through a transformer like in the previously described example of FIG. 2. The transformer is thus omitted been. There are two additional resistors R 12 and R: 13 in series between the an output of the rectifier and the connection point 24 are arranged. An additional Resistor R 14 is between bus 26 and terminal 8 of the operational amplifier 20 switched. The parallel combination of the relay RL 2 and the diode D 3, the in the embodiment of Figure 2 with the terminal 8 of the operational amplifier is connected, is here connected to the collector of a transistor T 1, whose Emitter connected to ground and its base connected to terminal 6 of the operational amplifier 20 is connected.

A diode D 5 is instead of the switch RLS 1 in series between the terminal 3 and the resistor R 4 are provided. The diode D 5 is used to provide a To prevent direct current flow from the windings to the protection circuit. The desk RLS 1 is a double contact switch, where a set of contacts make the connection between the resistor R 13 and the junction 24 controls while the second set of contacts the connection between the second output terminal of the rectifier 12 and mass controls. As a result, the operation of the relay RL 1 is activated the power source on the sensor-based connection or excitation of the motor high voltage decoupled from the rest of the protective circuit. It should be noted that the rectifier 12 is used in the direct current versions of the invention to an output of uniform desired polarity regardless of the input polarity to achieve.

The rest of the circuit is identical to that for all purposes the embodiment according to FIG.

The circuit of the embodiment according to FIG. 3 is characterized by operation with relatively high supply voltages between the terminals 1 and 2. The following component values differ from the component values given, for example, for the best possible mode of operation of the embodiment according to FIG. 2, these following component values being given as preferred examples. Where no new values are given, in a preferred embodiment the same values are used as in the embodiment according to FIG. 2 in conjunction with the following values: C 1 10 F / 350 V RL 2 PL 2 R 1 68 KOhm RS 28001 (Kaco Germany) R 10 R 14 1.5 KOhm R 11 R 6 33 KOhm R 12 R 13 6.8 KΩ / 1 W Reference is now made to FIG. 4, which shows an alternative embodiment of the sensor circuit for DC motors. The same designation as used in the description of the embodiment of Figure 2 is used for identical connections, and these are not specifically described below.

Connections +3 and -3 are each to a first and second motor winding coupled, the second winding being held at a potential relative to of the potential of the first winding is negative and is typically or

for example, differs by 220 V. A relay RL 1 is between the connections +3 and -3 switched. The connection +3 is via a diode D 6 with a connection point 50 connected. The junction 50 is through a resistor R 15 is connected to a junction 52, which in turn has a resistor R 16 is connected to a contact 61 of a relay-controlled switch RLS 1, the operation of which is controlled by relay RL 1. Terminal -3 is with one Contact 63 of the relay-controlled switch RLS 1 and via a Zener diode D 7 with the connection point 52 connected.

A storage battery, typically or preferably 12 V and 2 Ampere / h output capacity, which is labeled 60, is between the changeover contacts 65 and 67 of the switch RLS 1 switched. The switch RLS 1 is arranged or switched on, that he the respective battery connections either for recharging the battery with the respective contacts 61 and 63 or for proper operation with the respective contacts 69 and 71, each with the bus 26 and Ground connected, connects. The position of the changeover contacts is determined by the relay RL 1 in response to the connection or excitation of the motor that is monitoring is controlled to normal battery-powered operation of the sensor device to have when the engine is idle and to recharge the batteries when the Motor is switched on.

An additional resistor R 17 is in series between the capacitor C 2 and the input terminal 2 of the amplifier inserted, and a Zener diode D 8 is between the junction of resistors R 4 and R 17 and connected to ground.

The following component values indicate an operation of the embodiment according to FIG. 4 in the manner best known to the applicant or in a particular manner Preferred embodiment of the embodiment according to FIG. 4. Where no values are given, the same values are used in this case as in the above list for the particularly preferred embodiment of the embodiment according to Figure 2 apply.

R9 R3 R4 R5 R7 470 KOhm R8 R6 R 17 47 KOhm R 15 10 KOhm R 16 150 KOhm D 6 silicon diode 400 V0.5 AD 7 Zener diode 15 V 1/2 WD 8 Zener diode 15 V 1/4 W Reference is now made to FIGS of the present invention and an attachment means therefor. It is a particular feature of the present invention that the sensor circuit constructed and operable in accordance with an embodiment of the present invention be extremely compact.

According to one embodiment of the invention, the sensor circuit inside conventional overload protection devices that usually associated with large electric motors.

According to an alternative embodiment of the invention, which is shown in the Figures 5A and 5B illustrated, the sensor circuit within a compact junction box 80 are arranged, for example, a length of about 11 cm, a width of about 9 cm and a thickness of about 2 cm. The junction box is preferably made of highly impact-resistant plastic and provided with a bayonet type connecting fixture 82 on its rear side. At the front of the junction box are a plurality of connection terminals 84 and a warning light 86 that emits the light emitting described in the various circuits Diode or an external warning light to indicate low winding resistance may be provided.

It is often difficult to gain access to the back of an engine control box to drill mounting holes for a unit as shown in the present invention is provided. According to one embodiment According to the invention, a lateral mounting crosspiece 88 may be provided which a rear part 90 provided with an opening 92 and a side part 94, which runs at right angles to the rear part and in which a fastening slot 96 is formed, includes. This way, where there is a lateral attachment it is advantageous to have a mounting hole for one with the slot 96 in engagement bringing screw are drilled from the outside wall of a housing box.

Where a rear attachment is advantageous, the side part 94 can be broken away from the rear part 90 fairly easily.

Reference is now made to FIG. 6, which is a schematic illustration a sensor circuit which is particularly suitable for use in high-voltage AC motors is suitable that are operated with 2000 volts or a higher voltage.

The creation of such a protective circuit for motors that with such working at high voltages is a special feature of the present invention, since no protective circuits of this type are known for such motors.

The circuit of Figure 6 is generally similar to that already described above in connection with FIG Circuit, and those elements that are common to the two circuits are identical to Reference numerals are provided and will not be repeated at this point for the sake of brevity explained.

The main difference between the circuit of Figure 6 and that according to Figure 2 is that three identical resistors 100 between the respective Motor windings U, V and W and the connection 3 are provided. These resistances are selected so that they cause a sufficient voltage drop for the Sensor circuit is protected from the high motor winding voltages that are typical from line to line can be 2400 volts or even more.

Another difference between the circuit of Figure 6 and that of Figure 2 is that in the embodiment of Figure 6, a step-down transformer TR 2 is provided between terminals 4 and 5, which is connected to the motor control coil 30 are connected. The secondary winding of the transformer TR 2 is connected to a rectifier bridge 102 connected, the output of which is connected to a relay RL 1, the typical or is preferably a reed relay. In addition, instead of the capacitor C 1, a capacitor K 1 is connected between the collecting line 26 and ground.

Typical or particularly preferred component values for high-voltage operation of the circuit according to FIG. 6 are as follows: For operation at 2400 volts RLS 1 Relay and circuit according to the control voltage. High voltage reed relays of the type RA 3090 and HV 102 as well as V102, which are manufactured by the Magnecraft company are.

RL 2 relay Kaco 23.6 V direct current, measured nominal resistance 678 Ohm K 1 electrolytic capacitor 100 F. C 2 high quality capacitor 470 uF TR 1 transformer BVE1 30-Y7A T40 / E 220 / 24V 50 / 60Hz 1.8VA TR 2 n 1 12 bridge rectifiers: Minimum requirements PIV 100V, 100mA D 4 Zener diode 18V 5% 1W D 2 LED (as in the other units (LSM 6L - A) D 3 1 N 4004 p 1 20 operational amplifier CA 3094 (RCA) or Siemens TCA 315A or TCS 335A r 1 330 Ohm 1W r 2 200 K Ohm 18 r 3 3.4 M Ohm 1t r 4 1 M Ohm r 5 220 K Ohm r 6 33 K Ohm r 7 470 K Ohm 1% r 8 56 Ohm r 9 390 K Ohm 1% r ext 100 3 x 1 MOhm 2% 6W at 200C continuous operation, voltage 2000V effective It should be noted that when using the device at higher motor voltages the values of the resistors r ext 100 are increased accordingly can be.

The invention is of course not limited to the illustrated and preferred embodiments and examples described above, but it can be understood within the scope of the subject matter of the invention as it emerges from the Claims results, as well as within the scope of the general inventive concept in Realize with success in a variety of ways.

In brief summary, the invention relates to a low winding resistance protection system for electric motors, comprising a sensor device for coupling to at least one motor winding and one for comparing the winding resistance Motor, when it is at rest, with a predetermined threshold value, as well as for Generating a display output signal in response to exceeding this Threshold value; and a decoupling device for decoupling the at least one Motor winding of the sensor device in such a way that high voltages applied to the at least one motor winding can be applied during operation of the motor, not can reach the sensor device. One for use on high voltage motors suitable embodiment is also provided with the invention.

End of description.

L e r s e i t e

Claims (16)

Low winding resistance protection system PATENT CLAIMS Low winding resistance protection system for electric motors, indicated by a sensor device (20, U1, p1) for coupling or switching to at least one motor winding (U, V, W) and for comparison the winding resistance of a motor at rest (14, M) with a predetermined Threshold as well as generating an output indicator signal in response to a Exceeding this threshold value; and a decoupling device (RLS?) for Decoupling of the at least one motor winding (U, V, W) from the sensor device (20, U11p1) such that high voltages generated during operation of the motor (14, M) at the at least a motor winding (U, V, W) are present, kept away from the sensor device (20, U1p1) or switched off. 2. Device according to claim 1, characterized in that g e k e n n -z e i c h n e t that the sensor device comprises an operational amplifier (20, U1, p1). 3. Device according to claim 1 or 2, characterized in that g e -k e n n z e i c h n e t that it is designed for AC motors and a rectifier device (12, nu) includes which the control current received from an engine starter (30,32) in Converts direct current to feed the sensor device (20, U1tp1). 4. Device according to claim 1, 2 or 3, characterized in that g e -k e n n z e i c h n e t that the decoupling device has a relay-operated switch (RLS1 ) includes. 5. Device according to claim 4, characterized in that g e k e n n -z e i c h n e t that the relay operated switch (RLS to the coil (30) one with a motor (14, M) connected motor starter (30,32) is coupled to the connection or Determine excitation of the motor (14, M) by induction. 6. Device according to one of claims 1 to 5, characterized g e k e n It is not indicated that the decoupling device comprises a diode (D5). 7. Device according to one of claims 1 to 6, characterized g e k e n It does not indicate that you have a connection device (RLS 1) for optional production an electrical connection from a motor starter (30,32) to the sensor device (20, U1tp1). 8. Device according to claim 7, characterized in that g e k e n n -z e i c h n e t that the optional connection establishing a connection means relay-controlled switch (RLS 1), which reacts to the determined connection or excitement of the motor (14, M) with separation of the sensor device (20, U1, p1) responds to the engine starter (30,32). 9. Device according to one of claims 1 to 8, characterized g e k e n n e i c h n e t that they have a protective device (32, RL2) to prevent a Turning on or energizing the motor (14, M) in response to the output indicator signal includes. 10. Device according to one of claims 1 to 9, characterized g e k e It is noted that it has a display device (D2) for generating a visible Signal in response to the output indication signal. 11. Device according to one of claims 1 to 10, characterized g e k e n n z e i c h n e t that the sensor device (20, U1tp1) in a compact connection box (80) is arranged. 12. Device according to claim 11, characterized in that g e k e n n -z e i c h n e t that the connection box (80) with a warning light (86) or with a warning light device is provided to indicate a low winding resistance. 13. Device according to claim 11 or 12, g e k e n n -z e i c h n e t by a right-angled fastening cross-piece (88) which is arranged in such a way that that it can be attached to the side in or on an engine control box and on the rear part of which the junction box (80) is attached or attachable. 14. Device according to claim 11, 12 or 13, g e k e n n -z e i c h n e t by a fastening crosspiece (88), which is connected to the rear side of the Junction box (80) is engageable so that the junction box is optional on the side or on the back or on its side or on its back in or can be attached to an engine control box. 15. Device according to one of claims 1 to 10, characterized g e k e n n z e i c h n e t that the sensor device (20, U1tp1) in a conventional Overload protection block is inserted or added. 16. Device according to one of claims 1 to 15, characterized g e k e n n n z e i n e t that they are particularly suitable for operation at high voltages and a resistance device (100, Rext) of high capacitance or high resistance comprises, between the sensor device (20, U1, P1) and the at least one motor winding (U, V, W) is switched.