CN107643697B

CN107643697B - Control method of cooking utensil of periodic open type infrared oven

Info

Publication number: CN107643697B
Application number: CN201710220669.5A
Authority: CN
Inventors: 袁成; 赵双飞
Original assignee: Individual
Current assignee: Zhao Shuangfei
Priority date: 2017-04-06
Filing date: 2017-04-06
Publication date: 2020-12-04
Anticipated expiration: 2037-04-06
Also published as: CN107643697A

Abstract

The invention discloses a control method of a periodic discharge type infrared oven cooking appliance, the infrared oven cooking appliance comprises an oven ring, a thyristor is connected in series in an oven ring loop, the working state of the thyristor is controlled by a control signal sent by a control system, the control signal takes a time period T as a control period, the control period consists of a discharge time period T1 and a blocking time period T2, the duty ratio K = T1/T, the control system realizes the adjustment of the power of the oven ring by changing the value of the duty ratio K, the infrared oven cooking appliance working in the mode is matched with a filter circuit, and the whole machine can meet the electromagnetic compatibility requirements of standards such as connection, Harmonics, Flicker and the like.

Description

Control method of cooking utensil of periodic open type infrared oven

Technical Field

The invention relates to an infrared oven cooking appliance, in particular to a control method of the infrared oven cooking appliance.

Background

The harmonic current of Harmonics is a general name of each sinusoidal component of which the frequency is integral multiple of the frequency of the original periodic current when a non-sinusoidal periodic current function is expanded according to Fourier series. All nonlinear consumers generate harmonics, which distort the fundamental current and thus cause a failure of the distribution system itself or the devices. Harmonic waves in a power grid system refer to sinusoidal voltage or sinusoidal current with a frequency that is an integer multiple of the rated frequency of the power supply system. Harmonic disturbance is generally caused by devices having nonlinear voltage (or current) characteristics. Harmonic currents from different harmonic sources produce harmonic voltages on the power network, which harmonic currents (voltages) are usually vector-summed.

Flicker voltage change, voltage fluctuation and Flicker refer to the fluctuation of the voltage of a public low-voltage power supply system in normal operation of equipment, and are mainly determined according to the subjective severity of Flicker of a lamp with a 230V/60W spiral filament caused by the fluctuation of the power supply voltage. A large number of loads controlled by automatic on and off are connected to the power grid, such as kitchen appliances, electric heaters, air conditioners, copiers and other equipment with temperature controllers or timers, and when the automatic control cycle is switched on and off, the frequency of the power supply load changes, as a result of which the voltage of the power grid fluctuates; and the brightness of the lighting devices connected to the same network changes, which is easily annoying and healthy for some people (e.g. people with epilepsy). At present, various countries have strict standard requirements on electronic products such as reduction, Harmonics, Flicker and the like, and infrared oven cooking appliances serving as electronic products also have strict standard requirements on reduction, Harmonics, Flicker and the like.

The traditional control method of the infrared oven cooking utensil is realized by adopting a chopping mode or a mode of selecting half-wave conduction or a control mode of combining the chopping mode and the half-wave conduction. The thyristor works in a chopping control mode: a control method for applying power to a load by switching on a thyristor by selecting different electrical angles from 0 electrical angle to 180 electrical angles (of course, a negative half cycle between 180 and 360 degrees) in a single cycle of a mains supply. The harmonic test results generated when the thyristor works in a chopping state are shown in fig. 1 and fig. 2, in fig. 1, the sine waveform is the input voltage waveform of the whole machine, and the other waveform is the current waveform of the load, as can be seen from fig. 1, the thyristor is in a cut-off state in the period from the zero crossing point to the nearly 90 degrees electrical angle, and fig. 2 shows that the generated harmonic current is larger and far exceeds the allowable value of standards such as connection, Harmonics, Flicker and the like.

Another conventional control method is a control mode in which a thyristor works in a wave selection mode, and the working method is as follows: a control method for selecting the half-cycle to be switched on or off in a single cycle of the mains power from 0 electrical degrees to 180 electrical degrees (also a negative half-cycle between 180 degrees and 360 degrees). Fig. 3 and 4 show waveforms of operating voltages obtained across the load output by the thyristor in different operating modes of the wave selection. When the thyristor works in a wave selection state, Flicker generated due to the fact that the on-off frequency of the thyristor is too high cannot meet the standard requirement of electromagnetic compatibility. The thyristor works in a composite control mode of chopping and wave selection, and the standard requirements of connection, Harmonics, Flicker and the like cannot be met through actual tests.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a control method of a periodic discharge type infrared oven cooking utensil, which meets the requirements of electromagnetic compatibility standards (connection, Harmonics and Flicker) under the condition of meeting good user experience.

The technical scheme adopted by the invention for solving the technical problems is as follows:

a control method of a periodic discharge type infrared oven cooking appliance comprises an oven ring, wherein a thyristor is connected in series in an oven ring loop, the working state of the thyristor is controlled by a control signal sent by a control system, the control signal takes a time period T as a control period, the control period consists of a discharge time period T1 and a blocking time period T2, the duty ratio K = T1/T, and the control system realizes the adjustment of the power of the oven ring by changing the value of the duty ratio K, wherein T is more than or equal to 3000mS and less than or equal to 120000 mS.

Preferably, T ≦ 4000mS ≦ 60000mS, and most preferably T =4000 mS.

The infrared oven cooking utensil is provided with at least two oven rings, each oven ring loop is connected with a thyristor in series, and the working state of each thyristor is controlled by a control signal sent by a control system.

In the infrared oven cooking utensil with two oven rings, when the output power of the whole machine is less than or equal to the power of a single oven ring, one oven ring does not work, and the duty ratio of a control signal of a thyristor in the loop of the other oven ring is more than or equal to 0.10 and less than or equal to 1.00; when the output power of the whole machine is larger than the power of a single furnace ring, the duty ratio K of the control signal of the thyristor in one furnace ring loop is =1.00, the duty ratio K of the control signal of the thyristor in the other furnace ring loop is more than or equal to 0.10 and less than or equal to 1.00, and the working states of the two furnace rings are alternative.

The invention has the beneficial effects that: the control signal sent by the control system takes a time period T as a control period, the control period is composed of an open time period T1 and a blocking time period T2, the control system realizes the adjustment of the power of a furnace ring by changing the value of the duty ratio K, and the infrared furnace cooking utensil working in the mode is matched with a filter circuit, so that the whole machine can meet the electromagnetic compatibility requirements of standards such as connection, Harmonics, Flicker and the like.

Drawings

The invention is further illustrated with reference to the following figures and examples.

FIG. 1 is a waveform diagram of a load current in a chopped operating state;

FIG. 2 is a harmonic waveform diagram of the chopping operating state;

FIG. 3 is a waveform of a load current under a selected-wave operating condition;

FIG. 4 is a waveform diagram of the load current in the second selective operating mode;

FIG. 5 is a schematic diagram of a dual furnace ring circuit of an embodiment;

FIG. 6 is a waveform of the load current of the present invention;

FIG. 7 is a waveform of a load current at an embodiment control signal duty cycle of 0.2;

FIG. 8 is a waveform of a load current at an embodiment control signal duty cycle of 0.6;

FIG. 9 is a waveform of a load current at an embodiment control signal duty cycle of 1.0;

FIG. 10 is a table of the operating conditions of the dual furnace rings of the embodiment.

Detailed Description

Referring to fig. 5 to 10, a method for controlling a cooking appliance of a periodically-released type infrared oven, in which a whole period of commercial power is completely turned on or off from an electrical angle of 0 to an electrical angle of 360 (i.e., the upper half cycle and the lower half cycle of the whole period) in a single period of the commercial power, is referred to as a periodically-released type control method. The infrared oven cooking appliance comprises an oven ring, wherein a thyristor is connected in series in an oven ring loop, the working state of the thyristor is controlled by a control signal sent by a control system, the control signal takes a time period T as a control cycle (not equal to the cycle of alternating current), the control cycle consists of an open time period T1 (working time period) and a close time period T2 (close time period), the duty ratio K = T1/T, the control system realizes the adjustment of the power of the oven ring by changing the value of the duty ratio K of the control signal, wherein T is more than or equal to 3000mS and less than or equal to 120000mS (mS time unit millisecond), the starting points of T1 and T are the same, T1 is continuous, the starting points of T1 and T are the same, namely T1 and the timing zero point of T are the same, the continuous operation is continued according to the working mode of a periodic open type control scheme in the time period T1, namely in the time period T of, the interval T1 is continuous and not discrete accumulation, and in the time period T2, the control system turns off the control signal or outputs a low level signal, the thyristor is cut off, and no working current exists in the furnace loop. The thyristor can well meet the requirements of limit values such as harmonic waves, voltage change, voltage fluctuation, flicker and the like under the periodic discharge state.

The control period cannot be too long (the control period is set to be too large, the experience effect is poor), and cannot be too short (the electromagnetic compatibility requirement cannot be met), generally, T is more than or equal to 4000mS and less than or equal to 60000mS, and in the embodiment, T =4000mS is preferable.

In order to reduce the voltage variation of the system on the power grid in a low-power state, the infrared oven cooking utensil provided by the invention is provided with at least two oven rings (such as 2 rings, 3 rings, 4 rings and 5 rings), each oven ring loop is connected with a thyristor in series, and the working state of each thyristor is controlled by a control signal sent by a control system, so that the large current of a single ring is divided into a plurality of small currents which are independently heated to be independently controlled, and the impact degree on Flicker on the power grid is relieved.

In the infrared oven cooking utensil with two oven rings, when the output power of the whole machine is less than or equal to the power of a single oven ring, one oven ring does not work, and the duty ratio of a control signal of a thyristor in the loop of the other oven ring is more than or equal to 0.10 and less than or equal to 1.00; when the output power is greater than the power of a single furnace ring, the duty ratio K =1.00 of the control signal of the thyristor in one furnace ring loop, the duty ratio K of the control signal of the thyristor in the other furnace ring loop is not less than 0.10 and not more than 1.00, the infrared furnace cooking utensil is provided with at least two furnace rings, a thyristor is connected in series in each furnace ring loop, and the working state of each thyristor is controlled by the control signal sent by the control system.

Referring to fig. 10 (the control cycle is 4000mS, 10 gears, one furnace ring is an a ring, the other furnace ring is a b ring, "mS" is time unit millisecond, "W" is power unit watt, T1 is an open time period, i.e., a working time period, T2 is a blocking time period, i.e., a closing time period, and the gears can be equally subdivided according to the actual application design requirements, so that the gears evolve into 20 gears or even more), when the output power of the whole machine is less than or equal to the power of a single furnace ring (the power of the single furnace ring is 1000W) in the infrared furnace cooking appliances of the two furnace rings, one furnace ring (the b ring) does not work, and the duty ratio of the control signal of the thyristor in the loop of the other furnace ring (the a ring) is not less than 0.10 and not more than K and not more; when the output power of the whole machine is larger than the power of a single furnace ring, the duty ratio K of the control signal of the thyristor in one furnace ring (ring B) loop is =1.00, and the duty ratio K of the control signal of the thyristor in the other furnace ring (ring A) loop is not less than 0.10 and not more than 1.00. Due to the physical layout factors of the heating wires of the furnace plate, in order to obtain better user experience, the uniform heating effect needs to be obtained on the surface of the furnace plate, in the control mode, the working states of the two furnace rings are alternative, the alternative period is integral multiple of the control period, the working mode of the first ring is converted into the working mode of the second ring after one alternative period, meanwhile, the working mode of the second ring is converted into the working mode of the first ring, and the working states of the multiple furnace rings are also sequentially and alternately exchanged.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and should not be taken as limiting the scope of the present invention, which is intended to be covered by the appended claims.

Claims

1. A control method of a periodic discharge type infrared oven cooking appliance comprises an oven ring, wherein a thyristor is connected in series in an oven ring loop, the working state of the thyristor is controlled by a control signal sent by a control system, and the control signal takes a time period T as a control period, the control period consists of a discharge time period T1 and a blocking time period T2, the duty ratio K is T1/T, the control system realizes the adjustment of the power of the oven ring by changing the value of the duty ratio K, wherein T is more than or equal to 3000ms and less than or equal to 120000ms, the starting points of T1 and T are the same, T1 is continuous, the control system continuously works according to the working mode of the periodic discharge type control scheme in a T1 time period, the control system turns off the control signal or outputs a low-level signal in a T2 time period, and the thyristor is stopped;

when the infrared oven cooking utensil is provided with at least two oven rings, a thyristor is connected in series in each oven ring loop, and the working state of each thyristor is controlled by a control signal sent by a control system; the working states of the two furnace rings are alternate, and the alternate period is integral multiple of the control period.

2. The method of controlling a periodically released infrared oven cooking appliance according to claim 1, characterized in that T is 4000ms ≦ 60000 ms.

3. The method of controlling a periodically released infrared oven cooking appliance according to claim 1, wherein T-4000 ms.

4. The method for controlling a periodically-released type infrared oven cooking utensil according to claim 1, wherein in the infrared oven cooking utensil of two oven rings, when the output power of the whole machine is less than or equal to the power of a single oven ring, one of the oven rings does not work, and the duty ratio of the control signal of the thyristor in the loop of the other oven ring is not less than 0.10 and not more than K and not more than 1.00; when the output power of the whole machine is larger than the power of a single furnace ring, the duty ratio K of the control signal of the thyristor in one furnace ring loop is 1.00, and the duty ratio K of the control signal of the thyristor in the other furnace ring loop is not less than 0.10 and not more than 1.00.