BE1026793A1 - Device for controlling electrical devices - Google Patents

Abstract

Device for extending the service life of electrical systems working in a pulsed and cyclic manner.

Description

DEVICE FOR DRIVING ELECTRICAL APPLIANCES

Object of the invention

The present invention relates to a device making it possible to vary the intensity of filament or plasma lamps cyclically as well as electric motors while preserving their lifespan.

Technological background regarding lamps

The incandescent lamp.

In 1841, James Prescott Joule was the first to understand that in all electrical material there is heat release, it is the Joule effect. We use this law for lamps.

In the lamp, there are only two essential components:

- A metallic filament forming an electrical resistance and traversed by an electric current. This electric current is transformed into heat energy. Due to its high temperature, light energy is produced. And to prevent it from deteriorating on contact with oxygen, it is placed in an inert gas (argon). The filament was originally made of carbon heated to 1800 ° C, then it was tantalum (2000 ° C). Now it is made of tungsten: 2600 ° C. Despite the difference in materials, they all have the same lifespan of 1000 hours.

There are also double filament lamps: this increases light efficiency by more than 10% and reduces heat loss by convection or conduction.

- A gas which is a mixture of 2/3 of argon and 1/3 of nitrogen. By replacing argon with Krypton, we get a higher temperature and therefore a whiter light. Gas may not be used for lamps with a maximum power of 25 W.

Currently, the filament is approaching 2727 ° C (3000 ° K). The ideal would be by changing the material of the filament and the gas, to reach a temperature of 5727 ° C (6000 ° K) to reach a wavelength which corresponds to the best sensitivity of the eye, and therefore to a whiter light.

The incandescent lamp is available in a power of 25W, 40W, 60W, 75W, 100W or 1000W and in a voltage of 2.2V to 250V.

Halogen lamps

Halogen lamps can be used directly on a mains voltage and provide a bright white light avoiding the shadows cast in the light field. They can therefore replace incandescent lamps.

Halogen lamps can provide more than 35% more light when the axis of the filament is made to coincide with that of the reflector. They have a luminous flux of 24001m (for 100W).

BE2018 / 0105

Advantage:

* The improvement in performance relates to several criteria.

* Luminous efficacy: At equal power, more light is obtained.

* Light quality: A whiter, brighter and more intense light ensuring better color rendering. I.R.C. (Ra) = 100.

* Light constancy: The quality and quantity of light will remain practically identical throughout the life of the lamp.

* Double lifespan: Halogen lamps last (on average) at least twice as long as incandescent lamps.

An incandescent lamp does not have an unlimited lifespan, it can vary between 1000 and 2000 hours of use for current models. Certain lamps intended for very specific uses last only a few tens of hours (lamps for cinema projector) or on the contrary nearly a thousand hours (lamps for road signaling). A lamp ends its life by a breakdown during which the filament breaks.

Breakdown mechanism

During its use, the tungsten of the filament sublimates, which means that brought to high temperature (2800 ° C) it loses atoms which are found in gaseous form in the volume of the bulb. Its diameter therefore gradually decreases. Thinner embrittled areas appear than the rest of the filament.

However, these zones have a higher electrical resistance (the resistance increases when the diameter of the conductive wire decreases) and therefore heat up more. As their temperature increases, the sublimation phenomenon increases, they become thinner more and more until rupture. Filament breakage often occurs when the lamp is turned on due to thermal shock.

Regarding the evaporation of tungsten from the filament, it should be noted that the operating principle of halogen lamps is that the gas collects the evaporated tungsten atoms, and redeposits it on the filament (in crystalline form). Obviously, the deposit is made at a random location, which implies that holes always end up forming in the filament. There is also a phenomenon of transport of the tungsten in the axis of the filament and we observe a recrystallization of the filament. We can even see on the old lamps that the filament presents as facets, these are crystalline planes.

Tungsten, like all metals, has a lower resistance to cold than to hot (5 to 8 times lower). This state of affairs results in an overcurrent when the bulb is lit. The intensity of the current can then reach 10 times its normal value for a very short time (usually 1/6 of a second). There is therefore a peak current on ignition, which will quickly dissipate, upon incandescence

During this interval, while most of the filament gradually heats up, the thinner areas are brought to higher temperatures. The weakened areas of the filament can then rupture by mechanical expansion due to the rapid rise in temperature, this is breakdown. This explains why the lamps preferably flicker during ignition.

Once a region has started to evaporate more than the others, it will evaporate even faster because its resistance increases, its temperature will increase all the more.

There will therefore come a point where a fine area of the filament will be mechanically more fragile, or ^{BE2018 / 0105} then reach the melting temperature.

The progressive lighting of a lamp, using a dimmer for example, makes it possible to limit the consequences of this critical phase by reducing the intensity of the current flowing in the filament. A lamp fitted with a dimmer therefore has a longer life expectancy than another supplied directly from the mains.

The discharge lamp

The discharge lamp contains two electrodes embedded in a gas which when energized will be ionized and form a plasma.

When energized, this must be important to ignite the electric arc which will heat the gas and form the plasma. As soon as the gas cools, the arc will disappear. It will therefore be very difficult to operate this lamp in cyclic pulsed mode without keeping this gas hot.

PROCESS for lamps

According to the explanation above, if we want to flash a lamp by turning it on and then turning it off quickly, we will cause its premature wear.

However if, thanks to our process, we prevent it from going out completely by keeping the filament warm or by applying a minimum tension; the latter will only cool as much as possible and will not undergo the thermal shocks of its re-ignition and will last much longer.

If, moreover, it is applied to gradual variations in voltage and not abrupt peaks, it will last even longer.

EMBODIMENT regarding lamps

Figure 1 shows the voltage variations applied to the lamp according to the process.

The voltage ramp (numbered 0) represents the gradual lighting of this lamp; it is followed by repetitive cycles comprising three phases:

- The first (phase 0-1) during which the lamp is subjected to full voltage (Vn)

- The second (phase 2-3) during which the lamp goes down from full voltage to a voltage (Vm) to keep the filament warm

- The third (phase 4) during which the voltage gradually rises again to full voltage (Vm)

Then the cycle repeats.

FIG. 2 shows an embodiment, a voltage variator is connected and controlled by a signal generator, signals similar to those of FIG. 1. This variator is connected to a voltage source Vn. The level of the output voltage which powers the motor or the ^{BE2018 / 0105} lamp follows the alternating signals generated and are therefore similar to those in Figure 1.

According to the type of lamps and their power the levels of the two voltages Vn and Vm will be different; the same will apply to the slopes (speed of variation) of voltages 2 and 4.

With regard to discharge lamps operating in cyclic pulsed mode, to avoid having to re-strike the arc at each cycle, it suffices to maintain it by not lowering the voltage below the defusing threshold or to maintain the gas of the temperature lamp.

This embodiment has never been published but has been tested and will be implemented as soon as this patent application is filed on our Thermo + Debussy and Diasculpt devices

Technological background regarding electric motors

For low and medium power applications (up to a few kilowatts), the standard single-phase network is sufficient. For high power applications, the AC motors are generally powered by a source of polyphase currents. The most frequently used device is then the three-phase (phases offset by 120 °) used by electricity distributors.

These reciprocating engines are available in three types:

• Universal motors;

• Asynchronous motors;

• Synchronous motors.

These last two machines differ only by their rotor.

Universal motors

A universal motor is a DC machine with series excitation: the rotor is connected in series with the inductor winding. The machine torque is independent of the direction of current flow (torque proportional to the square of the current) and can therefore be supplied with alternating current. To limit the Eddy Currents which appear systematically in all massive metal areas subjected to alternating magnetic fields, its stator is laminated.

Universal motors are used in devices requiring a fairly high torque, such as a food processor, low-power power tools (up to 1200 W) or vacuum cleaners. The speed of rotation of these motors can be easily adjusted by an inexpensive device such as a dimmer (dimmer used to adjust the light intensity of the luminaires).

Synchronous machines

The synchronous machine is generally three-phase. As the name suggests, the speed of rotation of these machines is always proportional to the frequency of the currents which cross them.

t 1 · 1,, .... .... j ... il „.„ ,. J3E2018 / 0105

Synchronous machines are also used in traction systems (such as the TGV).

These machines are associated with current inverters, which makes it possible to fix the constant average motor torque with a minimum of current. We speak of autopilot (enslavement of stator currents relative to the position of the rotor).

Brushless motors

A brushless motor, or "brushless motor", is a synchronous motor, the rotor of which consists of one or more permanent magnets and to which is added a rotor position sensor (Hall effect sensor, synchro-resolver, incremental encoder for example). Seen from the outside, it operates on direct current. Its Brushless designation comes from the fact that this type of motor contains no brushes. However, an electronic control system must ensure the switching of the current in the stator windings. This device can be either integrated into the engine, for small powers, or external. The role of the sensor-electronic control assembly is to ensure self-piloting of the motor, that is to say the maintenance of a fixed angle between the rotor flow and the stator flow, role formerly v brush-collector assembly on a DC machine.

Brushless motors are used in particular in hard drives and DVD burners in our computers. They are also widely used in model making to move models of planes, helicopters and cars as well as in industry, in particular in the servo-mechanisms of machine tools and in robotics.

Asynchronous machines

The asynchronous machine, also known by the term "Anglo-Saxon" induction machine, is an AC machine without connection between the stator and the rotor. The term asynchronous comes from the fact that the speed of these machines is not necessarily proportional to the frequency of the currents which cross them.

The asynchronous machine has long been strongly challenged by the synchronous machine in high power areas, until the advent of power electronics. It is found today in many applications, especially in transport (metro, trains, ship propulsion), industry (machine tools), in household appliances. They were originally only used in engine but, still thanks to power electronics, they are more and more often used in generator. This is for example the case in wind turbines.

To operate in single-phase current, these machines require a starting system. For power applications, beyond a few kilowatts, the asynchronous motors are only powered by three-phase current systems.

Autosynchronous machines

These are synchronous machines whose starting is done asynchronously and when the rotation frequency is close to synchronism, the rotor clings to the stator field by synchronizing with the speed of the magnetic field. Autopiloting (control of the stator frequency as a function of rotor speed) tends to make this technology disappear.

Common characteristics of AC machines

BE2018 / 0105

With the exception of the universal motor, the speed of AC machines is generally related to the frequency of the currents flowing through them.

There are a wide variety of hybrid motors (eg "synchronous asynchronous" in dishwasher pumps).

Asynchronous motor

The motor at nominal voltage starts on its natural characteristics. At start-up, the motor is made up like a transformer whose secondary (rotor) is almost in short-circuit, from where the current peak at start-up.

This type of starting is reserved for low power motors in front of that of the network, not requiring a progressive setting in speed. The torque is energetic, the current draw is important (5 to 8 times the nominal current).

This start-up is not suitable if • The network cannot accept a voltage drop • The driven machine cannot accept brutal mechanical jolts • The comfort and safety of users are in question (escalator)

Universal motor

DC motors (dependent excitation) can be motor powered by alternating current. This universal motor is called (alternating or continuous). This type of motor is also used for vacuum cleaners, hand drills, razors, coffee grinders, etc., but also in traction motors (although the trend in this area is to use three-phase asynchronous motors with servo ).

In this motor, the inductors are also supplied by the network. If the polarity of the electric source changes, the magnetic poles of the inductors change as well as the direction of the current in the armature. The resulting force does not change direction, so neither does the direction of rotation.

However, when a DC motor is connected to a network of the same voltage U, we see that the current absorbed, the torque of the motor and its efficiency are much lower than continuously. It is also necessary to pay attention to the sparks on the collector which produces a heating.

To improve the functioning of this type of motor with an alternative supply, you must:

• Leaf through the stator (reduces losses by hysteresis and eddy current), • It is necessary to decrease the number of turns on the stator (decreases its inductance because it is greater in alternation) and increase that of the rotor to compensate for the loss of torque (due to the decrease in inductor flow).

• Do not use it for powers greater than 1 kW (poor motor quality due to poor switching).

The characteristic of this motor is that if the payload (power demand) increases, the speed of rotation decreases, which leads to a decrease in the counterelectromotive force

E 'and an increase in the induced and inductive current and therefore ultimately an increase in the ^inductive magnetic flux ^{E2018 / 0105} (therefore in the torque - we' replace 'speed with power).

Characteristics :

• If n decreases, Armature increases • If I increases, the torque increases (a lot) • The maximum speed can reach 30,000 min * ¹ (rpm) • Large torque at start-up

To change the direction of rotation of this motor, you must change the direction of the current either the armature or the inductor.

If the armature does not rotate, it behaves like a pure resistance (no E '). The starting current values are approximately 12 times the nominal value. To limit this current to an acceptable value, a rheostat (Radd) is generally placed in series with the armature.

PROCESS relating to electric motors

According to the analysis made above it is clear that during the start-up phase of any type of electric motor, a significant overcurrent occurs, causing it to heat up. If we want to run a motor in pulsed mode, it will therefore be necessary to move it away from its starting characteristics and to avoid stopping it during its pulsed operation. This is, in part, the object of this invention which makes it possible to rotate a motor in a pulsed and cyclic manner and continuously without significantly reducing its service life.

EMBODIMENT concerning electric motors

Figure 2 is an embodiment.

Instead of allowing the motor to stop between full voltage pulses, a minimum input voltage is applied to it to keep it always running at minimum.

To avoid mechanical shocks, overcurrents due to sudden speed variations, we will gradually go from full voltage to minimum voltage (example: half of full voltage) and vice versa.

The voltage curves shown in Figure 1 are still applicable.

This embodiment has never been the subject of any publication but has been tested and will be implemented from the present patent application on our Thermo + Debussy and Diasculpt devices

Claims (1)

BE2018 / 0105 CLAIM 1 Device allowing, during the operation in cyclic pulsed mode of electrical devices (M or L) having a high overcurrent at power-up, to limit the intensity at each of its power-ups at the start of the cycle, characterized by the fact that the applied voltage variations are pulsed but never fall back to zero so as to avoid overcurrent of the undervoltage current. CLAIM 2 Device according to claim 1, characterized in that this device can vary the speed of any electric motor in a pulsating manner while avoiding excessive heating given during each restart phase; device such that the voltage variations applied to the motor are pulsating but that their low threshold is such that it keeps the motor in motion and avoids the enormous restarting current which causes heating of the internal windings and their aging. CLAIM 3 Device according to claim 1, characterized in that it can vary the brightness of a filament lamp in a pulsating manner by avoiding the thermal gradients on the filament caused during each energization of the cold and conductive filament; device such that the filament is kept warm during the lowering phases. CLAIM 4 Device according to claim 3 such that the voltage variations applied to the lamp are pulsating but that their low threshold is such that it keeps its filament hot and limits the current which passes there during the phases of voltage rise knowing that the resistance is inversely proportional to the temperature. CLAIM 5 Device according to the preceding claims, characterized in that the voltage variations imposing the pulsating effect can be smoothed (slope of variation 2 and 4 obliques) to limit the current peaks and prolong the life of the motors and the lamps. CLAIM 6 Device according to claims 1 and 2 characterized in that the motor is any electric motor. ^CLAIM 7 ^{BE2018 / 0105} Device according to claims 1 and 2 characterized in that the motor is an alternating current motor. CLAIM 8 Device according to claims 1 and 2 characterized in that the motor is a series universal motor CLAIM 9 Device according to claims 1 and 2 characterized in that the motor is a direct current motor CLAIM 10 Device according to claims 1,3,4 and 5 characterized in that the lamp is a conventional filament lamp. CLAIM 11 Device according to claims 1, 3, 4 and 5, characterized in that the lamp is a halogen lamp. CLAIM 14 Device according to claims 1 and 3 characterized in that the lamp is a discharge lamp, in this case, it is not the filament but the internal gases which must be kept at temperature during the operating cycles. CLAIM 15 Device according to claims 1, 3 and 14 characterized in that in the case of a discharge lamp, the internal gases can be maintained in the form of plasma by avoiding bringing the voltage down to zero in cyclic pulsed mode. CLAIM 16 Device according to Claims 1 and 2, characterized in that if the phase (4) during which the voltage is below the nominal voltage level Vn is short enough that the temperature of the filament or the speed of the motor is still sufficiently high that in order not to cause a major overcurrent peak when the voltage is restored, the low voltage Vmin may be zero.