WO2007118576A1

WO2007118576A1 - Rectifier for supplying a brake coil

Info

Publication number: WO2007118576A1
Application number: PCT/EP2007/002604
Authority: WO
Inventors: Karl Unsin; Andreas Marten
Original assignee: Chr. Mayr Gmbh + Co. Kg
Priority date: 2006-04-10
Filing date: 2007-03-23
Publication date: 2007-10-25
Also published as: DE102006016748A1

Abstract

A circuit for operating a coil of an electrically released safety brake to connect to alternating current supplies with different operating voltages (preferably mono-phase) comprising: a rectifier circuit connected to the input terminals for the generation of a periodically changing direct current voltage; output terminals for supplying a coil with the direct current voltage generated by the rectifier; an electronic valve/switch, serving to switch the direct current on or off at any time; preferably a recovery diode, which is connected to the output terminals in order to maintain the current flow through the coil during the off-periods of the electronic valve/switch; a control circuit connected to the output terminals which measures the direct current voltage applied to the coil and which controls the electronic valve/the electronic switch in such a way that the direct current voltage applied to the coil remains constant; and a mechanical/electronic switch in the current feed to the coil for the purposes of the interruption and rapid cut-off of the free-wheeling circuit (Fig. 1).

Description

Rectifier for feeding a brake coil

Field of the invention

The present invention relates to a rectifier circuit for feeding a coil - for example, the electromagnet of an electrically releasable brake - with power from an AC network.

Technical background

Electrically released brakes, such as the safety brakes of elevators, generally consist of a brake that is forced into engagement with springs. In this context, "releasable" means that the brake is released or released by the action of the current: an electromagnet is provided to release the brake, it counteracts the spring force on an armature, but when de-energized, they bring Springs the brake back into engagement, for a significant proportion of the operating time of the The brake system on which the brake operates, therefore, the coil of the electromagnet must be energized, which requires a constant power supply. Typically, this is done by connecting to the local power grid. The voltage of the local power grid available near the machinery typically has one of a number of different default values. For example, they may be the 400V rotary or high voltage or 230 / 250V home networks in Europe or the lower HOV home networks found in the US. For any available voltage and braking power, the electromagnetically-released brake manufacturer must provide a suitable coil, which requires extensive stockkeeping of products that must be manufactured, maintained and maintained.

This problem of different line voltages is addressed in the document DE 19740 016 (corresponding to US 6 291 952), which describes an arrangement in which the average current flow through the coil is limited by an electronic switch. Since the magnetic effect of the coil is proportional to the current flowing through the windings, regulating the average current also regulates the magnetic field strength to the desired setpoint for releasing the brake, regardless of the voltage applied to the circuit as a whole , A disadvantage of this arrangement is that for each brake size, a separate limiting current must be set. The circuit provides no protection against thermal overload, which can occur when the effective resistance of the coil increases. Typically, the coil is energized for extended periods of time; she warms up therefore. With the warming their resistance increases. If the coil current is kept constant and the coil heats up, the power converted into it also increases, which raises its temperature further. To keep the current constant an even higher voltage is required. The increasing power and voltage can quickly lead to a failure of the coil. The aim of the present invention is a rectifier circuit for feeding electromagnetically releasable brakes, which can be used with different mains voltages. Preferably, the same electromagnetic coil and for all sizes of electromagnets the same rectifier circuit can be used for all voltages.

Summary of the invention

According to a first aspect of the present invention, this provides a circuit for feeding a coil with operating current, comprising:

Input terminals for connection to an AC mains; a rectifier circuit connected to the input terminals for generating a DC voltage based on the supplied AC current; and

Output terminals at which a DC voltage for connection to the coil is detachable at the rectifier circuit; characterized by a power supply control loop connected to the output terminals for measuring and regulating the voltage across the output terminals, the power supply control circuit having a control output line and an internal circuit for applying a request signal to the output line; if more power is needed from the rectifier to maintain the regulated voltage at the output terminals; wherein the rectifier element has a voltage limiting circuit connected to the control output line of the power supply control circuit and allowing a current to the output terminals when the request signal has been received.

According to a second aspect of the invention, this provides a circuit for operating a coil for connection to AC power supplies of different operating voltages, one with the input terminals

711m Fr7Piicrpn pinpr <? Irh npri nrii crh changing DC voltage; Output terminals for supplying a coil with the DC voltage generated by the rectifier; an electronic valve / switch with which a direct current can be switched on or off at any time; a freewheeling diode connected to the output terminals, with which the current flow through the coil can be maintained during the blocking periods of the electronic valve or switch; a control circuit connected to the output terminals, which measures the DC voltage applied to the coil and drives the electronic valve or the switch in order to keep constant the DC voltage applied to the coil; and a mechanical / electronic switch in the power supply of the coil, with which the freewheeling circuit is interrupted for an emergency shutdown.

The arrangement according to the invention regulates the voltage applied to the coil. If the temperature of the coil increases, the power converted in the coil decreases as a function of the resistance (P = U ² / R). This reduces the heating effect of the coil. Further, since the voltage on the coil is stabilized, the circuit can be used over a wide range of different supply voltages and for a wide range of coil currents. The arrangement also has the advantage that for each desired current only one of a rectifier and a coil voltage existing retrofit kit, but not a separate unit for each current / voltage combination is to produce. This achieves a drastically reduced number of manufactured and vorzuhaltender components. Even if one sets different target coil currents, but there is a fairly wide current range for a single rectifier circuit is sufficient. Other aspects of the invention include a conversion or retrofit kit from the rectifier and a brake coil and a full brake from the rectifier, the coil and the associated brake components such as the brake plates and the springs for engaging the brake. The design of such brakes themselves is known and can be found in several patent pending in the name of the applicant. description

There will now be some embodiments of the present invention

With reference to the accompanying drawings.

Fig. 1 is a circuit of the interconnected with a brake coil

Rectifier;

Fig. 2 is a circuit diagram of a second embodiment of the rectifier circuit also in Verschal device with a coil; and

Fig. 3 is a circuit of a third embodiment.

Fig. 1 shows a semi-controlled bridge. The measuring and control element controls the electronic switches Tl and T2 so that the nominal DC voltage is applied to the coil. The switch Sl is used for optional DC side shutdown. The voltage regulation can be done by phase control, phase sequence control or pulse width modulation (PWM). The switch Sl is used for optional DC side shutdown.

In the arrangement according to FIG. 1, therefore, the SCRs T1 and T2 replace the rectifiers in the positive half of the rectifier bridge. When power is required to maintain the coil voltage setpoint, the SCRs on their gate electrodes are energized to bypass the bridge rectifiers.

Fig. 2 shows a bridge rectifier circuit. The measuring and control element acts on the alternating voltage side on the electronic switch Tl, so that the setpoint DC voltage is applied to the coil. The voltage regulation can be done by phase control, phase control or pulse width modulation. The switch Sl is used for optional DC side shutdown.

In the arrangement of FIG. 2, a triac or other electrical AC- Bridge rectifier as needed and the control by the measuring and control element supply current.

Fig. 3 shows a bridge rectification. The measuring and control element controls the DC-side electronic switch Tl so that the target DC voltage applied to the coil. The voltage regulation can be done by phase control, phase control or pulse width modulation. The switch Sl is used for optional DC side shutdown.

In this arrangement, therefore, the AC input is applied directly to a bridge rectifier. The electronic switch, e.g. IGBT regulates the voltage applied to the coil on the DC side according to the signals from the measuring and control element.

In all the circuits described above can be parallel to the coil put a diode, which ensures the continuation of current flow after an interruption of the power supply. In series with this freewheeling diode may optionally be a switch that can be opened to ensure a maximum current drop of the coil current. Finally, a protection circuit can be installed which prevents an excessive increase in the return voltage across the coil, which could damage the electronics.

The "measuring and control element" in the block diagram can be an RC element with voltage divider for detecting the output voltage as well as an evaluation circuit that controls the electronic switches according to the level of the output voltage.It can be implemented, for example, with an operational amplifier or a microprocessor. The coil Y1 is preferably nothing but the coil itself, which changes its effective resistance due to the change in temperature, so that the coil current decreases when the coil voltage is kept constant.

For all of the embodiments described above, an optional up or down regulation of the control voltage is intended to achieve overexcitation and / or a reduced holding voltage. Typically, in the initial excitation, the coil is over-excited to build up the magnetic field as quickly as possible and kept energized at a reduced voltage after complete excitation. The circuit arrangements are suitable for any mains frequencies, including in particular 50 Hz or 60 Hz (for example USA). It has been found that mains voltages can be operated over a range of the order of 3: 1.

M 5333 HP / Cl

Claims

A circuit for operating a coil for connection to AC power supplies having different operating voltages (preferably single-phase), comprising: a rectifier circuit connected to the input terminals for generating a periodically varying DC voltage;

Output terminals for supplying a coil with the DC voltage generated by the rectifier; an electronic valve / switch to turn DC power on and off at any time; preferably, a freewheeling diode connected to the output terminals to maintain current flow through the coil during the off-time of the electronic valve / switch; a control circuit connected to the output terminals, which measures the DC voltage applied to the coil and controls the electronic valve / switch so that the DC voltage across the coil remains constant; and a mechanical / electronic switch in the power supply to the coil for interruption and quick shutdown of the freewheeling circuit.

2. A circuit according to claim 1, wherein the rectifier is designed as a half-controlled bridge circuit and the control elements (preferably thyristors, transistors, MOSFETs or IGBTs) are driven by the control circuit.

3. The circuit of claim 1, wherein the rectifier is designed as a bridge or half-wave rectifier and in the circuit of the output terminals of the coil, an electronic valve / an electronic switch (preferably thyristor, transistor, MOSFET or IGBT) is controlled by the control circuit ,

4. The circuit of claim 1, wherein the rectifier is designed as a bridge or half-wave rectifier and in the circuit of the input terminals an electronic valve / an electronic switch (preferably a triac) is located, which is controlled by the control loop.

5. A circuit according to any one of the preceding claims, wherein the control circuit is switchable to produce a higher voltage for over-excitation and a lower voltage for holding the electromagnet.

6. A circuit according to any one of the preceding claims, wherein the electronic valve / the electronic switch is controlled by the control circuit in phase or - section control.

7. A circuit according to any one of the preceding claims, wherein the electronic valve / the electronic switch is switched by the control circuit in pulse width modulation (PWM).

8. A circuit according to any one of the preceding claims, wherein in the freewheeling circuit of the coil is a switch (preferably mechanically or as an electronic valve / electronic switch)

9. A circuit according to claim 8 having a voltage-limiting electronic component (preferably a varistor, a zener diode or a suppressor diode) at the output terminals for limiting the turn-off voltage to the coil.

10. Electronically releasable brake or other electromagnetic components according to VDE580, with:

Springs that urge the brake pads to a braking condition; an electromagnet which is connected to counteract the forces of the springs and thus release the brake; and a circuit according to any one of the preceding claims, wherein the output terminals are connected to the coil of the electromagnet.

11. Method for controlling the terminal voltage of an electromagnet, comprising the following steps:

Connecting a rectifier circuit to a (preferably single-phase) AC power supply for generating a periodically varying DC voltage;

Feeding a coil with the DC voltage generated by the rectifier under the control of an electronic valve / switch to continuously turn on and off the DC power; preferably, connecting a freewheeling diode to the output terminals to maintain current flow through the coil during the off-time of the electronic valve / switch;

Measuring the DC voltage applied to the coil and driving the electronic valve / switch such that the DC voltage applied to the coil remains constant; and preferably interrupting the power supply of the coil in the freewheeling circuit for rapid shutdown.

HP / Cl m5333-besch + an