Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
VOLTAGE RECTIFIER, PARTICULARLY FOR SUPPLYING POWER TO DIRECT-CURRENT ELECTROMAGNETIC BRAKES, IN ELECTRIC MOTORS
Document Type and Number:
WIPO Patent Application WO/2010/081782
Kind Code:
A1
Abstract:
A voltage rectifier (1) for supplying power to direct-current electromagnetic brakes, particularly for application in electric motors, comprising a diode bridge (4) connected to the power supply (2), and means (7) for low-voltage power supply and for input voltage measurement, which are connected to the diode bridge (4), the low-voltage power supply means (7) being connected in turn to output voltage adjustment means (8), which in turn are connected to power transistor means (10) adapted to drive a coil (6) of an electromagnetic brake.

Inventors:
ZANOTTI VITTORIANO (IT)
Application Number:
PCT/EP2010/050222
Publication Date:
July 22, 2010
Filing Date:
January 11, 2010
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
ROSSI MOTORIDUTTORI S P A (IT)
ZANOTTI VITTORIANO (IT)
International Classes:
H02P15/02; H02K49/02; H02P3/04
Foreign References:
JP2005045936A2005-02-17
DE3710842A11988-10-20
JPH03169279A1991-07-22
Other References:
None
Attorney, Agent or Firm:
MODIANO, Micaela (Via Meravigli 16, Milano, IT)
Download PDF:
Claims:
CLAIMS

1. A voltage rectifier (1) for supplying power to direct-current electromagnetic brakes, particularly for application in electric motors, comprising a diode bridge (4) connected to the power supply (2), characterized in that it comprises means (7) for low-voltage power supply and for input voltage measurement, which are connected to said diode bridge (4), said low-voltage power supply means (7) being connected to output voltage adjustment means (8), which in turn are connected to power transistor means (10) adapted to drive a coil (6) of an electromagnetic brake. 2. The rectifier according to claim 1, characterized in that it comprises, between said output voltage adjustment means (8) and said power transistor (10), a circuit for controlling said power transistor.

3. The rectifier according to claim 1, characterized in that it comprises, between said power transistor (10) and said coil (6) of the electromagnetic brake, a circuit for protection against overvoltages, which is connected to said diode bridge.

4. The rectifier according to one or more of the preceding claims, characterized in that it comprises filtering means (3) between said power supply (2) and said diode bridge (4). 5. The rectifier according to one or more of the preceding claims, characterized in that said coil (6) of the electromagnetic brake is applied to an electric motor.

6. An electric motor with electromagnetic brake, characterized in that it comprises a rectifier according to one or more of the preceding claims.

Description:
VOLTAGE RECTIFIER, PARTICULARLY FOR SUPPLYING POWER TO DIRECT-CURRENT ELECTROMAGNETIC BRAKES, IN ELECTRIC MOTORS Technical Field The present invention relates to a voltage rectifier adapted to convert a voltage from alternating to direct in order to supply power to electromagnetic direct-current spring-applied negative brakes (braking upon power failure), particularly but not exclusively for applications with electric motors of the three-phase and single-phase asynchronous type in the so- called "self-braking" version. Background Art

As is known, in the applications of self-braking motors cited above, traditional diode-bridge rectifiers are used in the half-wave or full-wave form, with or without varistors, with or without speed-up function (momentary overvoltage at the brake coil) or others in order to reduce the brake unlocking or release time. However, in all cases there is a direct proportionality between the AC input voltage and the DC output voltage (Vdc = 0.90 Vac in the case of a full-wave diode bridge, Vdc = 0.45 Vac in the case of a half-wave diode bridge and momentary overvoltage equal to 0.90 Vac in the presence of speed-up).

In traditional rectifiers, the brake coil must be designed for a specific voltage and therefore it is necessary to know beforehand, during the ordering and manufacture of the motor, the operating voltage for the power supply of the brake (the country in which it will be used and, in the specific case of the three-phase asynchronous motor, whether phase-neutral or phase-phase power supply will be used for the brake).

This of course entails considerable costs, logistical and storage problems, as well as management and customer service costs.

Another drawback is constituted by the fact that the performance characteristics of the brake, in case of fluctuations of the power supply grid, are not perfectly constant, and further the condition of holding the brake released (which would not require the full power supply voltage) is provided by supplying the brake with the full voltage.

Disclosure of the Invention The aim of the present invention is to provide a voltage rectifier particularly for supplying power to electromagnetic brakes in electric motors that allows to have in output a voltage having a predefined constant value, which within certain limits is independent of the input voltage.

Within this aim, an object of the present invention is to provide a voltage rectifier that is substantially "universal" or "multi-voltage".

Another object of the present invention is to provide a voltage rectifier that can ensure greater constancy of the performance characteristics of the brake with which it is associated in case of fluctuations of the power supply grid. Another object of the present invention is to provide a voltage rectifier which, applied to a brake of an electric motor, ensures low energy consumption.

A further object of the present invention is to provide a voltage rectifier which, when associated with an electromagnetic brake of an electric motor, allows to reduce Joule-effect losses in the brake coil and therefore allows less heating and a shorter time during release and separation of the brake keeper from the magnet body.

Another object of the present invention is to provide a voltage rectifier that is highly reliable, relatively simple to provide and at competitive costs.

This aim, as well as these and other objects that will become better apparent hereinafter, are achieved by a voltage rectifier for supplying power to direct-current electromagnetic brakes, particularly for application in electric motors, comprising a diode bridge connected to the power supply, characterized in that it comprises means for low- voltage power supply and for input voltage measurement, which are connected to said diode bridge, said low-voltage power supply means being connected to output voltage adjustment means, which in turn are connected to power transistor means adapted to drive a coil of an electromagnetic brake. Brief description of the drawings

Further characteristics and advantages of the invention will become better apparent from the following detailed description of a preferred but not exclusive embodiment of the rectifier according to the present invention, illustrated by way of non-limiting example in the accompanying drawings, wherein:

Figure 1 is a block diagram of the rectifier according to the present invention applied to a coil of an electromagnetic brake;

Figure 2 is the circuit diagram related to the block diagram of Figure 1. Ways of carrying out the Invention

With reference to the figures, a device according to the invention, generally designated by the reference numeral 1 , comprises, downstream of a power supply grid 2, filtering means 3 connected to a diode bridge 4.

The diode bridge 4 is connected to means for low-voltage power supply and input voltage measurement 7, which in turn are connected respectively to means 8 for output voltage adjustment and for controlling a power transistor 10 and to the power transistor 10.

The output voltage adjustment means 8 are then connected to the power transistor 10, which in turn is connected to a coil 6 of an electromagnetic brake.

It is further possible to provide, between the power transistor 10 and the coil 6, a circuit for protection against overvoltages, which is not shown.

Substantially, the output voltage adjustment means 8 and the low- voltage power supply 7, which measures the voltage in input, allow to have an output voltage driving the power transistor 10 which is substantially independent of the input supply voltage and therefore of any fluctuations thereof.

This allows to have a universal rectifier, since the DC output voltage is stabilized in case of variable AC input voltages. Therefore, the rectifier allows to manage a single brake coil voltage in response to the different voltage requirements of the various countries of the world, such voltage being always coordinated with the voltage of the motor.

Moreover, with the device according to the invention it is not necessaiy to know whether the voltage used for the brake will be the one drawn between phase and neutral or between phases, or whether the motor will be destined for a particular country, since the brake is always suitable for the various voltages used.

Further, the device offers low energy consumption, because once the brake keeper has been attracted against the magnet body, since the condition for holding the brake released does not require the entire supply voltage, the voltage for holding the brake released can be adjusted and kept at a reduced constant value.

This leads to lower current consumption, lower loss due to Joule effect in the brake coil and therefore reduced heating, and further to a shorter time during release of the brake keeper from the magnet body.

Moreover, the device can be programmed to supply an initial voltage that is higher than nominal and then drop to the holding value, providing in practice intrinsically the previously mentioned speed-up function.

In practice it has been found that the device according to the invention fully achieves the intended aim and objects.

The device thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims.

The disclosures in Italian Patent Application No. MO2009A000006 from which this application claims priority are incorporated herein by reference. Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.