EP1899739A1

EP1899739A1 - Method for determining an asynchronous engine temperature and unit for controlling the power supply of an engine therefor

Info

Publication number: EP1899739A1
Application number: EP06755964A
Authority: EP
Inventors: Alain Tranchand
Original assignee: Somfy SA
Current assignee: Somfy SA
Priority date: 2005-07-01
Filing date: 2006-06-26
Publication date: 2008-03-19
Also published as: WO2007004002A1; FR2888057B1; FR2888057A1

Abstract

The invention concerns a method for determining the temperature of an asynchronous engine (MOT) comprising a permanent capacitor (CM) and two windings (W1, W2) and powered by a periodic voltage of period T. The invention is characterized in that it comprises an engine powering phase, followed by an electric quantity measuring phase (UC) in the engine while the engine is no longer powered and a phase for determining the temperature of the engine based on the variations of the measured electric quantity.

Description

Method for determining the temperature of an asynchronous motor and control unit of the power supply of an engine for its implementation.

The invention relates to a method for determining the temperature of an asynchronous motor defined according to the preamble of claim 1. The invention also relates to a use of the determination method.

For safety and fire prevention purposes, it is imperative that the temperature of the windings of an engine used in a building does not exceed a threshold set by the manufacturer or the standards. In the field of AC actuators using a single-phase permanent capacitor induction motor, this protection is commonly provided by an electromechanical device of bimetallic type. The protection is therefore reversible. The patent application WO 99/26323 gives an example of implantation of such a thermal protection. As simple as it is, this means of protection has many disadvantages. It requires a specific connection, low-voltage LV type (230V) imposing distances and insulation materials resulting in size and cost. The protection component itself is expensive to provide the necessary accuracy and reliability. Finally, the component does not give an intrinsic measurement of the winding temperature and even less of its average temperature since it is placed in a part of it (at the level of the buns). For example, US Pat. No. 5,850,131 is known in which an asynchronous motor with two coils and permanent capacitor is provided with a thermostat.

It is known in certain electrical devices to measure the temperature of a conductor from its resistance. Patent Applications JP 04369487 and JP 58095960 describe methods of measurement the temperature of a DC motor winding, by eliminating the effects of the back EMF of the motor and the voltage drops of the brushes.

Document US Pat. No. 4,413,325 also discloses a temperature measurement method based on the calculation of the resistance of the winding, this being determined by means of a complicated model and the measurement of numerous physical parameters (supply voltage, current phase shift / voltage, harmonics). The determination of the temperature is then carried out during the supply of the motor.

US Pat. No. 4,200,829 also discloses a device for controlling the power supply of an asynchronous motor comprising a means for detecting the crossing of a threshold by the temperature of a winding of the motor. This detection means comprises a resistor bridge in which one of the resistors is one of the motor windings. When the temperature of the winding varies, its resistance varies and when by variation of the resistance the bridge equilibrium, the power supply of the motor is cut off. This device does not measure a temperature but to detect a temperature threshold. In addition, it requires the use of many electronic components.

In the field of DC motors, US Pat. No. 6,111,330 discloses a measurement method using the evaluation of the blocking current of the motor from an integration of its starting current.

US Pat. No. 6,097,166 discloses a control device for an electric motor comprising a temperature sensor in the vicinity of the motor. The engine temperature is estimated according to the duration motor supply phases and the temperature measured by the sensor in the vicinity of the engine.

The object of the invention is to provide a method of determining the temperature of an asynchronous electric motor overcomes the aforementioned drawbacks and improving the determination methods known from the prior art. Thus, the invention proposes a simple temperature measurement method giving a value representative of the temperature of the motor windings. The invention also relates to a control unit allowing the implementation of such a method, the control unit having a simplified structure and a lower cost compared to control units known from the prior art.

The method for determining the temperature according to the invention is characterized by the characterizing part of claim 1.

Different embodiments of the determination method according to the invention are defined by the dependent claims 2 to 6.

The control unit according to the invention allows the power supply of an asynchronous motor with permanent capacitor. It is characterized by the characterizing part of claim 7.

The actuator according to the invention is defined by claim 8.

The actuator may comprise a non-reversible thermal protection means thermally coupled to the motor windings.

The method of determining the temperature of an asynchronous motor defined above can be used in a method of controlling the power supply of this motor. The appended drawing represents, by way of example, an actuator and a method according to the invention.

Figure 1 is an electrical diagram of an embodiment of an actuator according to the invention.

Figure 2 is a flow chart of an embodiment of a temperature determination method according to the invention.

Fig. 3 is a flow chart of an embodiment of a method of controlling an electric motor using the temperature determination method.

ACT actuator shown schematically in Figure 1 allows to drive a mobile element LD closing, occultation or sunscreen equipping a building. This element can be moved in two opposite directions by rotation of an induction motor MOT in a first direction of rotation and in a second direction of rotation. The actuator is powered by the power distribution network between an AC-H phase conductor and an AC-N neutral conductor. The movable element may for example be a roller shutter comprising an apron 2 consisting of blades, rollable on a winding tube 1 and having a lower end 3 movable between an upper extreme position 5 and a lower extreme position 4.

The motor MOT is single-phase asynchronous type, and comprises two windings W1 and W2. It is connected to a motor phase shift capacitor CM, or "permanent capacitor". According to the desired direction of rotation, the capacitor CM is arranged in series with the first winding W1 or with the second winding W2. We denote by P1 and P2 the connection points of the capacitor CM with each of the windings W1 and W2. The other two ends of the windings are connected to a point N1, itself connected to the neutral conductor AC-N via a controlled switch TRC, for example a triac.

A BRK immobilisation brake is associated with the MOT motor which blocks the rotor in the absence of current in the windings. As represented by dotted lines, the brake is magnetically coupled to each of the coils. When the motor rotor MOT rotates, it drives a gearbox GER, whose output stage drives a shaft constituting the mechanical output of the actuator.

The connection between the phase conductor AC-H and the windings W1 and W2 of the motor are effected by means of two switches rl1 and rl2 controlled by an electronic control circuit MCU which comprises various means ensuring the control of the actuator. that is to say means for receiving and interpreting orders received, actuator supply means and means for cutting off this supply either in order or when a stop is detected. The two switches rl1 and rl2 have a common connection, connected to the phase conductor at a phase terminal PO of the actuator. The other connections of the switches are respectively connected to the connection points P1 and P2.

The control of the controlled switches results from control commands transmitted by radio frequencies.

The electronic control circuit MCU comprises a CPU processing logic unit, such as a microcontroller. This circuit comprises a PSU supply circuit, typically a down converter, an input of which is connected to the phase terminal PO and whose other input is connected to the neutral terminal NO and constitutes the GND electric ground of the electronic control circuit. The DC output voltage VCC of the power supply circuit supplies the CPU processing logic unit and, not shown, a radio frequency receiver REC.

This radio frequency receiver REC comprises an RF input connected to an antenna ANT, and two logic outputs UP and DN respectively connected to two logic inputs 11 and 12 of the CPU processing logic unit. By means known to those skilled in the art, the radio frequency receiver interprets the received radio signal to generate, if necessary a high logic state on the first output UP or a high logic state on the second output DN, depending on whether the received signal conveys a climb order or a descent order.

The logic processing unit comprises a first output O1 supplying a first relay coil RL1 and a second output O2 supplying a second relay coil RL2. These coils act respectively on a first relay contact constituting the switch rl1 and on a second relay contact constituting the switch rl2. Depending on the relay coil energized, the MOT motor turns in either direction.

Other means than relays are usable, for example triacs or transistors. In a variant of the actuator, called wired control, the radio frequency receiver and the relays are removed. Connection points P1 and P2 are directly accessible from the outside of the actuator. The actuator rotates in a first direction when the phase conductor AC-H is connected, for example by means of a reversing switch, to the connection point P1 and turns in a second direction when the phase conductor is connected to the connection point P2. The electronic control circuit MCU comprises a torque control unit TCU whose first input U1 is connected to the conductor of the first winding W1 and a second input U2 of which is connected to the conductor of the second winding W2. These connections are symbolized by a circle surrounding the connection point. It is thus expressed that the connection is either constituted by a galvanic connection, and in this case the torque measuring unit TCU measures a voltage, or a phase shift of voltages, is constituted by a non-galvanic connection (for example inductive), and in this case the torque measuring unit measures a current, or a phase shift of currents. In the case of a galvanic connection, this is performed at the connection points P1 and P2.

Depending on the choice of the type of connection, the TCU torque measuring unit is therefore able to measure one or more of the following electrical quantities, when the motor is powered:

- Voltage across the capacitor CM,

- Voltage at the terminals of the first winding W1, - Voltage at the terminals of the second winding W2,

- Current in the first winding W1,

- Current in the second winding W2,

- Phase difference between one of the preceding voltages and one of the previous currents.

These electrical quantities are influenced by the value of the motor load. The torque control unit TCU, which is optionally supplied with voltage VCC by the power supply circuit PSU, outputs an OVL torque overload signal connected to an input 13 of the CPU processing logic unit. In the figure, the third input 13 is of logic type and the torque control unit TCU passes to the logic state high its OVL overload output if the torque exceeds a predetermined value and / or if the measured torque variation exceeds a predetermined value in a given time interval.

One embodiment of such a torque control device is described in patent FR 2 806 850, with reference to FIG. 1, from line 31 of page 4 to line 14 of page 6.

Alternatively, the torque control device TCU can deliver an analog voltage to the OVL overload output and the third input 13 of the CPU logic processing unit is of analog type. The processing of the study of the variations of this analog quantity is then carried out in the CPU processing logic unit.

The logic processing unit finally comprises a third output 03 controlling the controlled switch TRC. According to the states of the third output, the motor is non-powered or on the contrary the motor is powered at nominal voltage with the entire sine wave of the mains voltage, or powered at reduced voltage by a partially cut sine wave.

The advantage of the method according to the invention is that its implementation does not require the addition of any component to those which have been described with reference to FIG. 1. On the contrary, the method makes it possible to eliminate a switch of resettable thermal protection normally arranged on the conductor connecting the point N1 to the controlled switch.

An embodiment of the temperature determination method according to the invention is described with reference to FIG. 2. In a first step E1, the power supply of the motor is activated. To do this, the controlled switch is closed so as to supply the motor or, more precisely, to supply the electrical circuit formed by the capacitor CM and the two windings W1 and W2 of the motor. The relay RL1 or RL2 is first supplied to close the contact rl1 or rl2.

The closing of the controlled switch is triggered at a first predetermined time T1, in synchronism with the AC mains voltage. The instant T1 is for example defined as equal to 3T / 8 from the zero crossing of the sinusoidal voltage of the sector, where T is the period of this voltage. For such a choice, the powering up of the engine starts with the last quarter of an alternation.

In a second step E2, the TCU torque control unit is activated to measure a predefined electrical quantity. This quantity, denoted UC, is one of the voltages or currents mentioned above.

In a third step E3, the power supply of the motor is deactivated. To do this, the controlled switch TRC is open at a time T2. The opening is either controlled or occurs naturally for example because of the disappearance of the current in the switch. This is what happens if the controlled switch includes a triac, which naturally defuses when the current vanishes.

In a next step E4, the electrical quantity continues to be measured. Although the motor is no longer powered, this magnitude does not disappear since the electrical energy accumulated in the inductances L1 and L2 of the windings W1 and W2 and in the capacitor CM must dissipate in the resistors R1 and R2 of the coils. The duration of disappearance, or simply the time evolution, of the measured electrical quantity depends directly on the value of the resistances, therefore of the temperature of the coils. Since the resistances of the windings are generally equal to a common value R (strictly identical windings), this value R is therefore measurable from the time evolution giving the return to the idle state of the measured electrical quantity. It suffices, for example, to measure the time separating the first instant T1 and the instant T3 when the measured quantity falls below a predefined threshold.

In a step E5, the evolution of the quantity is used to derive information on the electrical damping of the circuit and to deduce the temperature of the windings. For example, the shorter the duration (T3-T1), the greater the damping, so the higher the resistance, the higher the average temperature of the coils. Therefore, a decrease information of the intensity of the physical quantity is used to deduce the temperature of the windings.

The method can use any electrical quantity whose value is changed over time after the opening of the controlled switch TRC.

It is not necessary to explicitly determine the temperature of the winding, but simply to obtain a magnitude which is the image.

The measurement procedure is all the more precise as the energy pulse supplied to the electrical circuit in the phase of supply of the transient regime is important. For this purpose, it is preferable to cause the controlled switch TRC to close when the amplitude of the mains voltage is maximum. However, such a choice can be made only if the engine does not present a brake immobilization of the type described above. Such a brake may no longer perform its function, for a very short time, if the engine is powered under full voltage. This explains the preferred choice of a value of the instant T1 at the end of alternation rather than at its maximum.

One embodiment of a method for controlling an electric motor is described with reference to FIG.

This method is activated by an action A11 representing a motion control. It begins with a step E11 of determining the engine temperature (or a magnitude representative of the temperature) using the temperature determination procedure described above.

In a next step E12, the duration of operation due to the command requested until the engine temperature becomes critical is estimated. Induction motors of the type used in the field of the invention have a current whose total intensity varies very little between the no-load operation and the load operation. For a given engine temperature, it is therefore easy to determine what is the duration of operation still possible before reaching the critical temperature.

The comparison of the duration of maneuver required by the command and the permissible maneuvering time is carried out in a step E13. If the control command involves a maneuver of a duration shorter than the permissible maneuvering time, the motor is supplied in a step E14. Otherwise, in a step E15, the motor is not powered. Alternatively, in step E15, the motor can be powered in a degraded mode that is to say that the order of operation is performed incompletely, the operation being limited by the maximum operating time allowed. The actuator can inform the user that he is in degraded mode, for example, by presenting repeated stops during his movement.

The actuator operating according to the method described above is protected against any risk of overheating due to excessive use or exceptional circumstances. However, the safety standards require that the actuator remains secure in the event that an electronic device is to be in default. This ultimate safety is obtained in the actuator according to the invention using a fuse protection means, therefore non-reversible, whose melting temperature is several tens of degrees higher than the monitored safety temperature prohibiting the operation of the engine. This fusible protection means, shown in dashed line under the reference TSW, is disposed between the points N1 and NO, while being thermally coupled to the motor windings, and has a much lower cost than that of a thermal protection switch. reversible normally arranged in the same place.

The method is preferably applied in the case where the electrical quantity measured in the engine is also used to determine the engine torque, but it can also be applied in the case where the electrical quantity is measured in the engine for another use, for example the monitoring of the mains voltage. In both cases, the means used do not entail any additional cost or congestion. The electrical quantity can also be measured for the sole purpose of the application of the method, with a specific electrical measuring means of voltage, current or phase shift, less expensive and / or less cumbersome than a thermal sensor. In all cases, the electrical quantity is a direct quantity (voltage, current, phase shift) relating to the motor elements (coils W1 and W2 and capacitor CM) and not an electrical quantity derived from a temperature sensor.

In the described method, the damping of the electrical magnitude is determined by continuous or sampled measurement of the magnitude. In a first variant, the quantity is simply measured once, after a predetermined duration, and compared to a threshold value stored in memory and corresponding for example to the temperature not to be exceeded. In a second variant, the quantity is applied to the input of a comparator and the duration is measured at the end of which the quantity falls below the comparison threshold.

Claims

Claims:

1. Method for determining the temperature of an asynchronous motor (MOT) comprising a permanent capacitor (CM) and two coils (W1, W2) and powered by a periodic voltage of period T, characterized in that it comprises a phase motor supply, followed by a measurement phase of an electrical magnitude (UC) in the engine while the engine is no longer powered and a phase of determining the engine temperature from variations in magnitude measured electric.

2. Method according to claim 1, characterized in that the electrical quantity is the voltage at the terminals of the permanent capacitor or at the terminals of one of the motor windings.

3. Method according to claim 1, characterized in that the electrical quantity is the intensity of the current flowing in the permanent capacitor.

4. Method according to one of the preceding claims, characterized in that the electrical quantity is used, during normal operation of the engine, for the determination of the engine torque.

5. Method according to one of the preceding claims, characterized in that the electrical quantity is used, during normal operation of the engine, for monitoring the mains voltage supplying the motor.

6. Method according to one of the preceding claims, characterized in that the engine power duration is less than a quarter of period T.

7. Unit (MCU) for controlling the power supply of a permanent capacitor asynchronous motor (MOT), characterized in that it comprises hardware means (CPU, TCU, RL1, rl1, RL2, rl2, TRC) and software for implementing the method according to one of the preceding claims.

Actuator (ACT) comprising a control unit (MCU) according to claim 7 and an asynchronous electric motor (MOT) with a permanent capacitor.

9. Actuator (ACT) according to the preceding claim, characterized in that it comprises a non-reversible thermal protection means (TSW) thermally coupled to the motor windings.

10. Use of the method for determining the temperature of an asynchronous motor according to one of claims 1 to 6 in a method of controlling the power supply of this engine.