DK171091B1 - Brake for a motor, preferably an AC motor - Google Patents

Abstract

In the case of a brake for a motor, in particular an alternating current motor with a solenoid, in order to improve the dynamic characteristics without increasing the power loss it is proposed to divide the coil of the solenoid (2) into two part coils (3, 4), by means of an intermediate tap (6), one of these two part coils being located on a freewheel circuit. <IMAGE>

Description

DK 171091 B1

The invention relates to a brake for a motor, in particular an AC motor, with an electromagnet and a rectifier coupling with freewheeling circuits and with a series coupling of a holding and accelerating coil for the electromagnet.

5

From DD-PS 82 158 there is known a brake by which the coil of the electromagnet is divided into two partial coils, namely a starting winding in a holding winding. The starting winding lies in a free-running branch containing a free-running diode, whereas the holding winding is not contained therein. Because of this measure, the free-running diode is permanently exposed to a high current. It is affected during the initial phase by the high acceleration current and later by the transformative effect of several times the operating currents. In addition, due to the high load loss, a short braking time for the brake is further achieved, but losses occur in the semiconductors, so that high-voltage diodes must be used, e.g. in series coupling, and with several selenium surfaces respectively silicon diodes with zener diodes. This method is thereby only suitable for systems with low operating voltage and electric load, but not for large braking motors; for during the acceleration phase, the current commutes at each half-wave of the diode from the thyristor and vice versa. The switching process from the diode to the thyristor results in an extreme current load in this coupling.

US-PS 30 87 104 discloses a braking system with a current transformer in which the total brake control load must be applied. The transferred load depends on the load and the size of the motor respectively. The engine starting current provided is used for rapid magnetization. DE-PS 32 23 260 only shows a coupling device for interrupting the idle currents.

DK 171091 B1 2

The object of the invention lies in the further development of the brake described initially, that while maintaining the dynamic advantages of reducing the semiconductor load, using it at higher loads.

Inventively, the said task is solved by a brake of the type mentioned initially by the fact that only the holding winding lies in the freewheeling circuit.

10

Through the inventive device, the inevitable losses occur not in the semiconductors but in the coil. The heat of loss is thereby considerably easier to carry away. The diode is only slightly loaded, so that the cost of the semiconductor becomes less 15 and yet large voltages and loads can be used. Thermal advantages are also obtained and, in addition, the biased acceleration coil provides ideal protection against surges, as well as a reduction of the commutation current peaks, thereby effecting a radio attenuation 20 through the device by the series coupling of acceleration coil and diodes provided in the holding winding. A current load from the semiconductor elements due to scattering inductances between the transformer coupled windings does not occur. The switch of the acceleration coil 25 is substantially relieved, and can also operate at very low inclinations with very small inclinations. This gives an increased service life of the coupling and further follows that no over-dimensioning of the thyristors is necessary.

30

At the same time, through the inventive embodiment, the dynamic properties of the brake are greatly improved; it can be manufactured at low cost. The brake has a low wear and a high durability of the brake lining as the coating due to the rapid influence of the brake from the high switch-on current by electromagnetic influence of the air force becomes less worn. During the engagement of the brake, the voltage is applied to a portion of the coil, and thereby the current will only pass through this portion and be high enough that sufficient current is supplied by the action of the anchor disk; in particular, the voltage drops across the total coil so that a lower holding current is applied due to the increased resistance. In preferred embodiments, it is contemplated for this purpose that the acceleration coil is in series with an acceleration switching switch connected parallel to another holding coil which can be engaged via an associated control element. The control element is preferably designed as an on and off switch. As long as the switch, which is preferably an electronic switch, such as a thyristor, is connected, the unidirectional current flows through a coil part, namely the acceleration coil and the thyristor. The barrier of the thyristor is provided by a current through both coils, and through the increased resistance causes a reduction in current flow. When the motor is switched off, whereby the brake is to be actuated, the free-running diode's holding winding is inserted so that the magnetic field can be built up in this coil after the interruption. The breaking time of the brake becomes independent of the acceleration clutch through the small time constant in the holding coil 25, and also in case of failure of this very short. In order to accelerate the switch-off, it is further envisaged in a manner known per se that the free-running circuit is carried out high-ohmically, with the electronic switch being blocked, so that the current after the switch-off is applied to a resistor, such as a varistor connected in parallel to the coupler . The latter switch is connected in a manner known per se through the coupling located on the motor. This, however, after the output of the motor, even generates a generator voltage which delays the locking of the said switch.

In order to achieve an instantaneous shift and thus a better dynamic damping of the brake even when the motor is switched off and when the brake is switched on, it is proposed in a preferred further embodiment that a current transformer connected to a brake transformer is connected to a power supply circuit. control circuit for a switching contact located in the 10 brake coil current circuit. Thus, inventive risk of coupling the magnet as a control signal to open the brake circuit, does not reduce the voltage, but decreases the motor current, which, in contrast to the voltage immediately after switching off the motor supply, is suppressed, e.g. by switching on a relay, thereby reducing the decoupling time further. In further embodiments, it is contemplated that the control circuit comprises a Schmitt trigger and that a diode is connected antiparallel to the load switch, thereby providing the diode with additional protection of the coupler, in particular a polarity reversal fuse on a field power transistor.

As an alternative to the DC side known per se in the high-ohm circuit of the freewheeling circuit, the invention further proposes a countercurrent magnetization, so that a preferred embodiment of the invention is distinguished by the provision of a countermagnetizing branch circuit with a switching countercurrent circuit. Hereby, the motor induction residual voltage is utilized at the motor shutdown to actuate the countercurrent brake. It should be noted that if the motor after the shutdown does not present any residual voltage, so that no countercurrent influence of the brake will follow, this will correspond to a switch-off on the alternating current side, whereby the brake, in its design according to the invention, will be activated without delay. quickly.

A switch-off on the alternating current side of a DC-supplied coil is known per se, where the coupling contact, however, belongs to a motor protection for switching on and off the mains voltage. However, the disadvantage of this is that the motor protection must be provided with an extra switching contact to the brake coil and with extra connecting wires from the motor protection to the brake coil coupling circuit, which is why the above-mentioned switching off on the DC side is proposed on the basis of the residual voltage of the motor, which is what they provide above. disadvantages. Therefore, according to the invention, it is proposed to engage the coupling switch on the alternating current side 15 of the brake coil voltage supply circuit and to take out the coupling signal via a current transformer located in the brake motor voltage supply circuit. The switching contact is a circuit breaker, especially a triac.

In a further preferred embodiment, according to the invention, an alternating current side separation is proposed, so that by removing the switching signals over a current transformer arranged in the braking motor voltage supply, the braking coil voltage supply is switched.

The switch is a load switch, preferably a Triac.

Further advantages and features of the invention can be deduced from the claims and the following description, in which 30 preferred exemplary embodiments of the inventive braking device, with reference to the drawings, are explained in more detail.

DK 171091 B1 6

The invention is further explained below in connection with the drawing, in which: FIG. 1 shows a first embodiment of the invention; FIG. 2 is a schematic representation of the brake and the motor with the one shown in FIG. 1; FIG. 3 is a clutch circuit for improving the dynamics of brake application; FIG. 4 shows an alternative embodiment of the control circuit of FIG. 3 and 15 in FIG. 5 shows a preferred installation option for a switch according to FIG. 3 or 4,

As shown schematically in FIG. 1, the invention comprises an electromagnetic brake 1 having an electromagnetic 2 having two 20 part coils 3 and 4, between which there is a branch location 6. The overall coil 2 is preferably designed such that the two sub coils 3 and 4 are wound radially over one another and at a convenient location made to the branching site 6. The sub-coil 3 has a resistance of approx. half or 25 third of the resistance of the sub coil 4. Furthermore, there is a one-way rectifier coupling 7 with two rectifier diodes VI and V2, of which diode VI is arranged as a free-running diode parallel to the sub-coil 4. Diodes VI and V2 are connected in parallel with varistors R1 and R2 as surge protectors. Furthermore, there is a third varistor R3, the function of which is further elucidated in FIG. 2, which is connected in series with the brake coil 2's high-resistance freewheel circuit when the brake is switched off.

DK 171091 B1 7

At the branching point in series with the sub coil 3, a thyristor TH is further coupled which causes the sub coil 3 to be switched as an acceleration coil. The thyristor TH is turned on through an on / off switch 12, which is an RC circuit 5 (not shown) that applies the ignition signal for a desired period of time. To retract the on / off clutch 12 at low voltages, a monitoring unit 13 is provided whose operation depends on the sizing of the brake. The unit 13 preferably operates according to principle 1 with relative voltage measurement, so that the function of the device is independent of the voltage supply. The dimensioning of the sub coils may be such that without coupling the current passing through the coil 2 does not allow the brake to be commissioned. Thus, by this measure, the same coil as in FIG.

15 1, a "more powerful" brake is applied to a larger engine.

The FIG. 1, as shown in Fig. 1, operates as follows: 20 When the mains voltage is applied, and thus the motor 21 is switched on, the thyristor TH is switched on as an electronic switch so that the acceleration coil 3, due to the small resistance of the coil 2, runs a larger current. which produces a greater magnetic flux, and thus a faster operation with a short reaction time. Following the reaction of the brake magnet, the high magnetic flux is no longer necessary as the air gap between the anchor and the magnetic coil and thus the magnetic resistance is reduced. Thus, inferior holding forces are required, and thus inferior magnetic currents and inferior holding currents.

After the reaction, the thyristor TH is blocked by the on-off coupling 12 so that the mains current flows in the total coil, ie. both sub-coils 3,4, thereby being unidirectional through the rectifier consisting of the opposite directional diodes VI, V2. Due to the greater resistance of the total coil 3.4, a lower holding current, which results in lower energy consumption and, when switched off, results in a faster switching.

During one half wave of the AC power, the current flows through both sub-coils 3 and 4 as well as the diode V2, while the other half-wave is interrupted by the diode V2 and a 10 freewheeling circuit over the diode VI is released, over which the energy of the coil is degraded. Only in this embodiment is an improvement in the dynamics of the brake 1 compared to a conventional brake with the same heat generation and in particular a shortened drop-out time.

15

The inventive braking device, as shown in FIG.

2, obtain a further fast interrupt by means of a high-ohm coupled free-running circuit through the varistor 3. 1 2 3 4 5 6 7 8 9 10 11

Further, for rapid disconnection or rapid 2 decomposition of the inertia of the brake coil, a 3 counter-magnetization can be provided, as shown in FIG. 1 is indicated by dotted 4 lines. To this is also provided a thyr 5 large TH ', antiparallel to the thyristor TH connected to a switch electronics in (not shown) electronics 12.

7

The thyristor TH 'switches the negative half-wave in the grid, 8 which lies above the acceleration coil 3. The voltage comes 9 from the motor, so that a temporary control is not necessary.

10

The counter current supply leads to rapid demagnetization of the 11 system and thus to rapid braking operation. The thyristor Th 'can thereby be used in a suitable manner, e.g. through a current sensor T1, shown in FIG. 3, be turned on. The switch of FIG. 3, replaces the control line and switch contact in a "DC separation" of FIG. 2nd

DK 171091 B1 9

FIG. 2 shows a decomposable motor 21 with connecting lines L1, L2 and L3 to the phases R, S and T. of an AC network. In the connecting lines LI, L2 and L3 there is inserted a motor protection Kl, which is arranged to be able to switch off and switch on the motor 21 on online. From two of the lines, here L2 and L3, connecting lines 22 and 23 lead to the braking device of FIG. 1. Furthermore, there is provided a switch-off switch 10 at the motor protection K1 for switching contact 24 in the free magnet circuit of the lifting magnet 2. The coupling switch 24 can be switched on in a conventional manner in the event of a voltage failure by switching off the motor 21 from the motor guard K1 or by the one shown in FIG. 3, the control coupling 26 described is connected via the motor current, as also shown in FIG.

2. The coupling contact 24 is connected in parallel to that of FIG. 1 varistor R3. When the motor guard K1 disconnects the motor 21 from the grid, it is broken through the switching contact 24 of the varistor R3, so that the free flow current flowing over the idle diode VI is limited to a value of variable R3, such that the lift magnet 2 will bring the brake 1 to a correspondingly fast attraction.

The switch 24 in the free-circuit circuit of the lifting magnet can be part of a control coupling, as shown in FIG. Third

25

The FIG. 3, the coupling 26 shown in FIG. 3 is preferably designed as an auxiliary equipment in a separate housing, which can be designed as shown in FIG. 5.

The control coupling 26 has four connection points. Input terminals 31 and 32 are used for connecting the coupling circuit 26 in one of the connecting lines of the motor 21, in fig. 2 wire L3. The essential component of control circuit 26 is a current transformer T1 such that the circuit comprises the root current and not the voltage applied to the motor 21. The output terminals 33 and 34 of the control circuit 26, which are connected to the coupling switch 24, which in the illustrated embodiment is designed as a field power transistor, are used to connect the auxiliary equipment in the lifting circuit 2 of the lifting magnet 2. The coupling switch 24 can be connected to an antiparallel diode V8 to obtain additional protection against a polarity conversion at the line connection. Using a field effect transistor, this has already integrated the diode (as a parasite component).

Furthermore, the control circuit 26 comprises a bridge rectifier 37 with two diodes V4 and V5 and two Zener diodes Z1 and Z2 - the latter of which are used for voltage limitation - and a 15 Schmitt trigger D1, which is configured in a corresponding coupling via an integrated component 4093 . Further, there is a filter structure R4, R5 and C1 for filtering out the wave frequency of the rectifier rectified signal from the current transformer T1. The Schmitt trigger D1 is energized 20 through a diode V6 and a capacitor C2 which ensures that there is always a sufficient supply voltage for the Schmitt trigger. Furthermore, a protection diode V7 is provided. 1 2 3 4 5 6 If the motor 21 is now switched off because the motor protection Kl breaks 2 there, also the leads 22 of the brake 1 and 22 (Fig. 2) 3 become inoperative, so that the brake should drop. However, such a 4 rapid drop-off is delayed by the generator voltage produced at the engine switch-off. Furthermore, 6 at the disconnection in the brake coil, a free-flow current arises which delays the pull of the brake 1. However, when the motor protection K1 switches off the motor, the power supply in the lines LI - L3 is disconnected, so that the coupling contact 24 via the control circuit 26 connected in the line L3 171091 B1 11, the instantaneous lowering of the Schmitt trigger voltage is immediately transferred to the locked state so that (Fig. 2) the free flow current flowing over the free-release diode VI of the brake coil 2 flows against the varistor voltage, whereby the braking system is quickly avoided by the magnetic energy. that the brake drops even faster.

As soon as the motor 21 is switched on again, that is, connected to the mains and the current flows, the control circuit 26 10 is reconnected.

The function of the device shown in FIG. 4 switches are as follows: -

The FIG. 3, the coupling circuit shown in Fig. 3 can preferably be designed as an auxiliary equipment in a separate housing, which can be formed of standard components such that the auxiliary equipment can be mounted by screwing on the thread for a cable entry at the motor terminal box, avoiding the use of a larger terminal box than the conventional ones.

20

The intermediate outlet 6 at the brake coil 2 and the arrangement of the free-circuit current over the sub-coil 4 with the free-flow diode VI instead of the hitherto preferred DC separation allows the same result to be obtained by an alternating current-side separation for a small additional cost. For this purpose, a coupling circuit 51 as shown in FIG. 6 with terminals 52 and 53 corresponding to the circuit of FIG. 3 for connection in a line L3 to the motor 21. Above the output terminals 54 and 56, the circuit is connected alternately 30 in one of the supply lines 22 and 23 of one of the brake coil 2 (Fig. 2). Furthermore, the circuit 51 comprises again a current transformer To which feeds a rectifier with diodes Vil and V12 and for voltage limitation two Zener diodes V13 and V14. To short-circuit an always short-circuit voltage breakdown in the AC signal, a capacitor C11 is provided. The voltage smoothed by the current transformer To and the capacitor C11 is applied to the control input of a triac V15 connected in parallel with a 5 varistor Ril. When switching off the power supply to the motor, the power supply to the brake coil 2 via the current transformer To is immediately disconnected by blocking the triac V15 or via the varistor Ril to a value not large enough to hold the brake. In this embodiment of the invention, so far, by alternating current side separation, disadvantageously required separate wires, for example for fuse contacts, have been redundant.

FIG. 5 shows a constructive configuration for receiving 15 additional couplings, especially with current transformers as used in FIG. 3 and 4, without having to use larger terminal boxes.

In addition to a cover 62, a conventional terminal box 61 has a number of internal threaded cable glands 63 and which are lockable via external threaded end plugs 20 64 when not in use. In such a pass-through 63, an additional housing 66 is screwed in with a thread 67, which is closed on the front side with a cover 68. In the illustrated embodiment, the auxiliary housing is designed as a reducer or auxiliary piece, in which a front fitting is screwed in -25 seen end cap over an intermediate pack of gaskets, such as a 0-packing ring.

In FIG. 5 indicates 71 a clamp plate and at 72 the brake rectifier is disposed. 73 denotes a terminal block. The cable guides are not shown in detail.

Claims (11)

Brake for a motor, in particular an AC motor, with an electromagnet (2) and a rectifier coupling (7) with a free circuit, and with a series coupling of an electromagnet holding (4) and acceleration coil (3), characterized in that: only the holding winding (4) lies in the freewheeling circuit. 10 Brake according to claim 1, characterized in that the acceleration coil (3) is in series with an acceleration coupling contact (Th) connected parallel to the second holding coil (4), which can be switched via an associated control element (12). Brake according to claim 1, characterized in that the surge protection elements (RI, R2) are connected to the rectifier coupling (7). 20 Brake according to claim 3, characterized in that each surge protection element (R1, R2) is connected in parallel with a diode (VI, V2) in the rectifier (7) and is in the free circuit. 25 Brake according to claims 2-4, characterized in that at least one part coil (3,4) is coupled as the control element's forward resistance (12) to the acceleration coupling contact (Th). 30 Brake according to claims 2-5, characterized in that the control element (12) for the acceleration switching contact (Th) is a time relay element. DK 171091 Bl Brake according to claims 1-6, characterized in that in the voltage supply circuit (Li - L3) of the brake motor (21) a current transformer (TI) connected to a control circuit (26; 51) for a in the brake coil 5 is inserted. (3.4) power circuit located on-off switching switch (24; Tr). Brake according to claim 7, characterized in that the control circuit comprises a Schmitt trigger (37). Brake according to claim 7, characterized in that the coupling contact (24) is antiparallel connected to a diode (V8). Brake according to claims 7-9, characterized in that 15 on-off coupling switch (24, Tr) is connected in parallel to a voltage limiter. Brake according to claims 1-6, characterized in that a counter-magnetizing branch circuit with a switching contact (Th ') is connected antiparallel to the acceleration coupling switch (TH) 20 for countercurrent magnetization.