EP3478024A1 - Switching on of a heating load - Google Patents

Abstract

The invention relates to a method for switching on a heating load (LOAD), the heating load (LOAD) being controllable by means of phase control and the current phase control being characterized by a control angle (Õ1,..., Õn). In order to enable an efficient cold start with any heating load, the following steps are suggested: €¢ Switch on the heating load (LOAD) using a definable initial cut angle (cpINIT), €¢ Determination of the following gating angles (Õ 1 ,..., Õn) taking into account a determined effective current (I EFF ) and a definable switch-on current curve (I Start ). The invention also relates to a heating control system for carrying out the method according to the invention.

Description

The invention relates to a method for switching on a heating load, wherein the heating load can be controlled by means of a phase control method. The phase angle is characterized by a lead angle. The invention further relates to a heating control system for carrying out the method according to the invention.

Such a process is particularly useful in industrial heating processes, e.g. for curing paints and tempering of workpieces, in the automotive industry or in the plastics processing industry.

Often, radiant heaters are used there, whose cold-start characteristics result in very high currents. For example, radiators with a PTC thermistor characteristic to call, for. Tungsten-halogen lamps. In order to enable a safe and fast start when starting such radiant heaters or other heating applications with such unfavorable cold start properties must be ensured that existing fuses are not overloaded and / or maximum currents or services are not exceeded. So far, regardless of the heat load used, a phase control has been used which uses a very conservative and fixed sequence of bleed angles.

The lead angle is the angle that describes the proportion of a half-wave with a duration of 180 ° which strikes a load. The bleed angle is also referred to as the ignition angle, esp. Thyristors or triacs. There is also a so-called phase-section method, which could be used analogously to the phase-angle method, with the difference that the half-wave is cut off at the end and not at the beginning.

Since different radiators with different starting characteristics are used, in the previous methods either the fixed angular sequence must be chosen very conservatively or be determined each time on the basis of the radiator.

Object of the present invention is to enable an efficient cold start with any heating loads.

• Einschalten der Heizlast mittels eines festlegbaren initialen Anschnittwinkels und
• Ermitteln der folgenden Anschnittwinkel unter Berücksichtigung eines ermittelten Effektivstroms und eines vorgebbaren Einschalt-Stromverlaufs.

The task is solved by the following steps:

• Switching on the heating load by means of a definable initial bleed angle and
• Determining the following bleed angle taking into account a determined RMS current and a predefinable switch-on current curve.

The definable initial bleed angle is to be chosen so that it can be concluded on the basis of the resulting current conclusions on the current resistance of the heating load. However, the resistance of the heating load does not have to be calculated by itself, but the current can be used as a representative. Using this current can be determined and / or calculated for the following lead angles, which load is possible to allow the most effective, fast turn-on without overloading the system or any fuses. It makes sense to choose as large as possible initial lead angle, because so too much power is avoided. An RMS current may be, for example, the RMS value of the current over a half-wave or over several half-waves. It is also possible to use only individual measured values or instantaneous values in the half-wave as the basis for the RMS current and thus as the basis for the calculation / determination according to the method presented. The method thus makes it possible, regardless of the heat load used, automated to achieve the best possible order of ignition angles during cold start.

In the following it is explained by way of example how the RMS current to be taken into account can be included in the calculation of a following RMS current to be taken. $$I_{N+1}=\sqrt{\frac{I_{\mathit{SETn}+1}^2\cdot \left(t_N+t_{N+1}\right)-I_N^2\cdot t_N}{t_{N+1}}}$$

I_N+1

den zu stellenden folgenden Effektivstrom, also der gemäß des Einschalt-Stromverlaufs zulässige folgende Halbwellen-Effektivwert, aus dem der folgende zu stellende Anschnittwinkel/Zündwinkel ermittelt werden kann,

I_setN+1

den Sollwert zum folgenden Nulldurchgangszeitpunkt gemäß des Einschalt-Stromverlaufs,

I_N

den zu berücksichtigenden Effektivstrom (z.B. ein mittels Hall-Sensor gemessener Gesamt-Effektivstrom seit Beginn des Einschaltvorgangs),

t_N

die bisherige Gesamtdauer des Einschaltvorgangs und

t_N+1

die Dauer der folgenden Halbwelle.

It describes:

I _{N + 1}

the following RMS current to be set, ie the following half-wave rms value, which is permissible according to the switch-on current characteristic, from which the following leading angle / firing angle to be set can be determined,

I _{setN + 1}

the setpoint at the following zero-crossing point in accordance with the switch-on current profile,

I _N

the RMS current to be considered (eg a total RMS current measured by Hall sensor since the start of the switch-on process),

t _N

the previous total duration of the switch-on and

t _{N + 1}

the duration of the following half wave.

The equation is to be considered as a possible embodiment and can be simplified by empirical values or entirely as a lookup table, e.g. for different fuses or general heating load types.

The predefinable switch-on current curve predefines a current profile which, based on boundary conditions, results in definable and increasing effective currents. As boundary conditions here come, for example, the cold start characteristic of a radiator and a maximum load capacity of a fuse in question.

In a further advantageous embodiment, the heating load has PTC thermistor properties. The present method can be carried out particularly advantageously, since the heating load is often present, for example, as a tungsten halogen lamp and therefore exhibits a pronounced PTC behavior. This means that when the radiator or the heating load is switched on for the first time, very large currents can occur, with the present method, without further configuration, enabling the heating load to start as quickly as possible.

In a further advantageous embodiment, the initial bleed angle is at least 60 °, 90 ° or 120 °. The larger the lead angle, the lower the proportion of the half wave that hits the heat load. That the larger the lead angle, the lower the resulting current. This particularly conservative design prevents the maximum load capacity of a fuse or the entire system from being exceeded when the heating load is switched on for the first time. The subsequent bleed angles can thus be determined from the first determined approximation of the behavior of the heating load.

In a further advantageous embodiment, the following bleed angles are calculated and / or determined from the determined effective current. This can be done for example by means of a look-up table or a calculation using knife values.

In a further advantageous embodiment, the initial bleed angle is selected depending on a temperature of the heating load. This has the advantage that already preheated heating loads can be started even faster. A restart of a slightly cooled heating load is also facilitated. In the case of a PTC thermistor, the warmer it is, the more current can be given directly to the PTC thermistor. So, a less conservative choice of the first initial bleed angle is necessary.

In a further embodiment, the predefinable inrush current does not exceed a characteristic of a fuse. The goal of the fastest possible power-up process is to set the maximum current while maintaining system integrity. If the predefinable inrush current curve is adjusted on the basis of the characteristic curve of the fuse, then it is ensured that the fuse survives the switch-on process unscathed, and thus the integrity of the system is ensured. The fuse can be a single fuse in a power output, but it is also conceivable that the fuse is a higher-level fuse.

It is particularly advantageous if the predefinable inrush current does not fall below a predefinable minimum distance from a characteristic curve of a fuse. This ensures that the fuse remains intact and is a reserve for special cases, e.g. Overloads, foreseeable.

In a further advantageous embodiment, the switching on, ie the switch-on, is terminated when a lead angle of 50 ° or less has been reached. Thus, if a full wave or approximately one full wave can be switched, it is to be assumed that the operating temperature of the heating element has been reached and is now determined by a different driving method, e.g. Half-wave control, can be applied.

In a further advantageous embodiment, the switching is terminated when a lead angle has been reached which is smaller than an angle predetermined by the controller for the operation after the switch-on. If a phase control is still used after switching on, the method for switching on a heating load can be ended if the method can already supply higher currents than would be required by the control. This is expressed, for example, by falling below a desired value for a required lead angle.

In a further advantageous embodiment, the heating load is activated after switching on by means of a half-wave control. There are also other common alternative types of taxation conceivable.

In a further advantageous embodiment, the method for switching on a heating load is performed again when a definable cooling time is exceeded. This makes it possible to always perform an optimal and fast activation or switching on the heat load even when only sporadically used heating loads.

In a further advantageous embodiment, the method is carried out again every time the heating load is switched on. Since the method according to the invention can be carried out extremely efficiently and quickly, each switching-on process of the heating load can be carried out with the method. This further increases the reliability and security of the system.

The object is further achieved by a heating control system comprising a power unit and a controller, wherein the power unit is designed for controlling a heating load by means of phase control, wherein the phase control is characterized by gate angle and wherein the controller controls the power unit such that the heat load by means of a definable initial Bleed angle is turned on and the following bleed angles are determined taking into account a determined RMS current and a predetermined turn-on current waveform.

FIG 1

einen schematischen Stromlaufplan eines Leistungskanals,

FIG 2

zeigt den Zusammenhang von Anschnittwinkel und Effektivwert des Stroms über eine Halbwelle und

FIG 3

eine Auslösekennlinie einer Sicherung sowie einen Einschaltstromverlauf gemäß des vorliegenden Verfahrens.

In the following the invention will be described and explained in more detail with reference to the embodiments illustrated in the figures. Show it:

FIG. 1

a schematic circuit diagram of a power channel,

FIG. 2

shows the relationship between lead angle and rms value of the current over a half wave and

FIG. 3

a tripping characteristic of a fuse and an inrush current according to the present method.

FIG. 1 shows a schematic circuit diagram of a power channel, as it could be used with the inventive method. The central component is a switch T1, which is designed here, for example, as a triac, thyristors or other power semiconductors are also conceivable. Also visible is a switch T2, which is designed here as an opto-triac and for galvanic decoupling of the power channel is used by a controller CTRL. Furthermore, the input voltage U _{IN is} shown, which can be measured by means of a first voltage measuring device MU1 and subsequently a fuse FUSE, which protects the power channel. The current flowing through the first switch T1 is measured in the current measuring device MI. An output of the power channel OUT is provided with a second voltage measuring device MU2, wherein a heating load LOAD is connected to the output OUT of the power channel. It is particularly advantageous that the voltage measuring devices MU1, MU2 are not necessary for the method according to the invention. These have been shown for completeness and can, for example, be used for additional plausibility of the procedure and for additional functionalities.

If the control CTRL a corresponding signal, the opto-triac T2 ignites and the triac T1 is thereby ignited. The load OUT is then supplied with the input voltage U _IN and a current that adjusts according to the actual resistance of the load LOAD flows. The current measuring device MI can be designed as a Hall sensor and provide current readings available. The first voltage measuring device MU1 is used to measure the input voltage U _IN , the voltage measuring device MU2 is used for the measurement the voltage across the load. The control CTRL can perform a phase control or phase control, as well as other known methods, such as PWM or modifications. For example, fuse FUSE may be a fuse having a corresponding fuse characteristic as in FIG. 3 shown. Backup manufacturers often specify so-called time-current characteristics, from which it can be seen how long a certain current effective value can flow on average before the fuse triggers.

FIG. 2 shows the relationship between lead angle φ and effective value I _{EFF of} the current over a half-wave HW. In the upper diagram, a normalized power in percent% is plotted on the vertical axis, both diagrams extend over a half period from 0 ° to 180 °. The lower diagram shows the amplitude AMP, which is also normalized from 0 to 1 here. The upper diagram shows the actual RMS current I _EFF and the corresponding power P. The lower diagram shows a corresponding half-wave, for example the voltage half-wave HW. By way of example, a lead angle φ of 120 ° is selected. If it is assumed that the current follows an ideal sinusoidal shape over time, the result for the selected ignition angle is an effective value of approximately 44% of the effective value I _EFF .

FIG. 3 shows on the basis of a section of a tripping characteristic FUSE _{max of} a fuse FUSE, as with the help of determined by the method gate angles a predetermined switch-on current waveform I _{start to} be approximated and tracked as quickly as possible.

The tripping characteristic shown is a characteristic which _applies an effective _current I _EFF with respect to the melting time T _MELT . The inrush current profile I _Start has a predetermined distance DIST from the maximum current-time characteristic FUSE _max . By a parallel displacement here the distance DIST could be further reduced to achieve an even faster turn-on. This would have decreased Reserves and should therefore be taken into account when designing the system. The initial ignition angle φINIT leads to a low first RMS current I _EFF , so that it can be determined directly after the first ignition, which subsequent load is permitted. Already with the first bleed angle φ1, the current is brought to the predetermined inrush current. With the other bleed angles φ2 to φ5, the inrush current course I _{start is} correspondingly pursued and an effective and fast start-up procedure is possible without endangering the fuse FUSE or the power channel or even the entire heating system. Here, the RMS current I _rms I _start approaching to each of the other lead angle φ2 to φ5 successively to the inrush current. Due to the PTC thermistor characteristic, the resistance of the heating load decreases with increasing temperature and the lead angles φ2 to φ5 can be adjusted accordingly.

• Einschalten der Heizlast LOAD mittels eines festlegbaren initialen Anschnittwinkels ϕINIT,
• Ermitteln der folgenden Anschnittwinkel ϕ1,..., ϕn unter Berücksichtigung eines ermittelten Effektivstroms I_EFF und eines vorgebbaren Einschalt-Stromverlaufs I_Start. Die Erfindung betrifft weiterhin ein Heizungssteuerungssystem zur Durchführung des erfindungsgemäßen Verfahrens.

In summary, the invention relates to a method for switching on a heating load LOAD, wherein the heating load LOAD can be controlled by means of phase control and wherein the respective current phase angle is characterized by a leading angle φ1, ..., φn. To enable an efficient cold start with any heating loads, the following steps are proposed:

• Switching on the heating load LOAD by means of a definable initial lead angle φINIT,
• Determining the following lead angle φ1, ..., φn taking into account a determined effective current I _EFF and a predetermined turn-on current waveform I _start . The invention further relates to a heating control system for carrying out the method according to the invention.

Claims (14)

Method for switching on a heating load (LOAD), wherein the heating load (LOAD) can be controlled by means of phase control, wherein the respectively current phase angle is characterized by a lead angle (φ1, ..., φn), comprising the steps: Switching on the heating load (LOAD) by means of a definable initial angle of incidence (φINIT), • Determining the following bleed angles (φ1, ..., φn) taking into account a determined effective current (I _EFF ) and a predefinable switch-on current characteristic (I _Start ). The method of claim 1, wherein said heating load (LOAD) has PTC characteristics. Method according to claim 1 or 2, wherein the initial lead angle (φINIT) is at least 90 ° or preferably at least 120 °. Method according to one of the preceding claims, wherein the initial angle (φINIT) following the leading angle (φ1, ..., φn) from the determined RMS current (I _EFF ) are calculated and / or determined. Method according to one of the preceding claims, wherein the initial bleed angle (φINIT) is selected depending on a temperature of the heating load (LOAD). Method according to one of the preceding claims, wherein the predeterminable switch-on current characteristic (I _start ) does not exceed a characteristic (FUSE _max ) of a fuse (FUSE). Method according to one of the preceding claims, wherein the predefinable switch-on current profile (I _start ) does not fall below a predefinable minimum distance (DIST) from a characteristic curve (FUSE _max ) of a fuse (FUSE). Method according to one of the preceding claims, wherein the switching is terminated when a lead angle (φ1, ..., φn) of 50 ° or less has been reached. Method according to one of the preceding claims, wherein the switching is terminated when a lead angle (φ1, ..., φn) has been reached, which is smaller than a predetermined by the controller (CTRL) angle for the operation after the switch-on. Method according to one of the preceding claims, wherein the heating load (LOAD) is activated after switching on by means of a half-wave control. Method according to one of the preceding claims, wherein the method is performed again when a definable cooling time of the heating load (LOAD) is exceeded. Method according to one of the preceding claims, wherein the method is performed again each time the heating load (LOAD) is switched on. Heating control system comprising a power unit and a controller,
wherein the power unit is designed to control a heating load (LOAD) by means of phase control,
wherein the phase angle is characterized by lead angle (φ1, ..., φn) and
wherein the controller activates the power unit such that the heating load (LOAD) is switched on by means of a definable initial angle of inclination (φINIT) and
the following gating angle (φ1, ..., φn) (I _EFF) taking into account an effective current detected and a predeterminable switch-on current profile (I _start) determined. Heating control system according to claim 13 for carrying out a method according to one of claims 1 to 12.

Images