WO2001008289A1

WO2001008289A1 - Method for supplying quasi-constant current, quasi-constant voltage to ac electric applications and apparatus of the same

Info

Publication number: WO2001008289A1
Application number: PCT/CN1999/000096
Authority: WO
Inventors: Lifa Yuan
Original assignee: Guangdong Provincial Special Economic Zones Industry Co. Ltd.; Great Sino Industries Limited
Priority date: 1998-01-21
Filing date: 1999-07-21
Publication date: 2001-02-01
Also published as: CN1058817C; CN1224271A

Abstract

A power supplying loop is comprised of a load assembly, which is included at least one load R and a normal-closed switch K in parallel with it, and a capacitor C connected the load assembly in series so as to supply power to the load R when open the switch K. This power supplying loop has the feature of supplying quasi-constant current or quasi-constant voltage, that is, for maintaining varying magnitude of the current through the load or the voltage across the load not exceeding predetermined percentage. The apparatus or method of the invention supplies power with simple structre, no harmonic pollution. It reduces loss and gain multiple functions with lower cost, these functions include short circuit or overload protection; running low-voltage electric appliances on high-voltage electric network; preventing impacting current from damaging electric applications and extending the lifetime of them; compensating a power factor for electric network in situ; turning on/off loads without sparking to ensure safety and blast-prool etc.

Description

Method and device for power supply of quasi-constant current and quasi-constant voltage control AC electrical equipment

The present invention relates to the field of power supply devices for alternating current electrical appliances, and in particular, to a method and device for controlling power supply of alternating current electrical appliances with quasi-constant current and quasi-constant voltage.

Background technique

At present, there are many types of AC electrical appliances, each of which has its own performance and characteristics. Usually, when it is operated under the direct power supply of the grid, it will bring or have many problems. Taking lighting appliances as an example, ordinary incandescent lamps are the most commonly used. The main reason for lamps is that their color rendering is close to that of sunlight, and the color rendering index is close to 100%, but the service life of incandescent lamps is short, especially the low-power incandescent lamps powered by the mains voltage have a shorter life. Disadvantages. Incandescent lamp damage often occurs when the current is turned on and the filament breaks. Low-voltage operating bulbs are beneficial to improve light efficiency and prolong life. However, a special voltage-reducing device, such as a transformer, is required to reduce the voltage. It not only adds an energy loss source, but also increases the possibility of failure (such as a transformer short circuit). The emergence of low-pressure tungsten halogen lamps has increased the light efficiency and life of these lamps, but the fatal weakness is that their operating voltage is low, and the above-mentioned step-down devices and their various problems have followed. Another type of electrical appliances, like televisions and lamps, are almost everywhere. They often fail. The most serious is short circuits. Not only do they burn components, electrical appliances cannot work, but they can also cause fires. In the case of televisions, the power supply is the source of many faults. Today's television power supplies mostly use switching power supplies. The high voltage after rectification of the mains voltage is directly applied to the switching circuit. Components on this type of circuit are therefore easy to be hit. The common protection method is to add a fuse, but due to the deviation of the fuse value and the lag action, the accident may have been caused before the fuse is blown. It can be seen from the above examples of the two types of electrical appliances that their shortcomings and problems are multifaceted, and a method that can comprehensively solve these problems is needed.

Summary of the Invention

The object of the present invention is to provide a method and a device for controlling the power supply of an alternating current electrical appliance with quasi-constant current or quasi-constant voltage. This method and device can avoid working conditions that affect its life extension, so that it does not cause serious consequences caused by failures. It is safe, reliable, simple, and inexpensive, enabling some electrical appliances to work under energy-saving and efficient conditions.

The quasi-constant current or quasi-constant voltage referred to here means that the current or voltage provided to the consumer is constant in the engineering sense, that is, its variation is within the allowable specified range.

The technical solution of the present invention is a method for controlling power supply of alternating current appliances with quasi-constant current, which is characterized by:

1. Connect a normally closed switch at both ends of an electrical consumer in parallel as a load component;

2. Connect at least one of the above load components in series with each other, and then connect in series with a device having a capacitance C and connect it to the grid line end;

3. By opening or closing the normally closed switch of any one or several of the load components, the corresponding electrical consumers are connected to or disconnected from the power grid;

4. Select the capacitance value of the above capacitors so that the loop current of all load components when the normally closed switches are closed is For standard current values, when all normally closed switches are open, the voltage across the load components in series meets the voltage requirements of the load, and the loop current is the lower limit of the allowable range. A quasi-constant voltage control method for power supply of alternating current electrical appliances, which is characterized by:

2. Connect at least one of the above-mentioned load components in series with each other, and then connect in series with a device having a capacitance C and connect it to the power grid line end;

3. Connect or disconnect the corresponding electrical consumers from or to the power grid by opening or closing the normally closed switch of any one or more of the load components;

4. Use the lower limit value of the allowable voltage fluctuation as the voltage across the load, determine the voltage across the capacitor based on the required loop current and the mains voltage, and select the capacitance value of the above capacitor. A quasi-constant current or quasi-constant voltage controlled AC power supply device is characterized in that: a normally closed switch is connected in parallel at both ends of an electrical device to form a load component, at least one of the above load components is connected in series with each other, and has a capacitance The devices of C are formed in series. In order to explain the operation of the method and device of the present invention, the following explanation is made by using an electrical appliance as a resistor. The circuit configuration of the device of the present invention is shown in Figure 1. The impedance triangle of the circuit when resistive load is shown in Figure 2a, and the corresponding voltage triangle is shown in Figure 2b. Its three sides correspond to the grid voltage U ~ and the capacitor terminal voltage t / _e. , And load voltage, the switch K in Figure 1 is a normally closed switch, that is, the load is closed when it is not working. If the percentage of current change is allowed in the quasi-constant current range, and-, the standard value of the loop current is / ~, let the current in the capacitor circuit / ~ when the normally closed switches at both ends of the consumer are closed, then ^ LJ ^ is the capacity of the capacitor When the load ^ is switched on by opening the switch, the loop current is set to the lower limit of the allowable change / ~, at this time

U _R = U-UJ II \ UJ-(ai

That is, the device of the present invention having the capacitor with the capacitance determined by the above formula can ensure that the loop current changes from / ~ to when the load resistance value changes from 0 to R (ie, from short circuit to full load). 1 ~ At this time, the load power changes from 0 to W _R , and the current change does not exceed the allowable percentage. Increasing the load power of the device of the present invention under the condition of the set capacitor will not further increase the current. This is the watt limiting function of the device of the present invention. This function of limiting the amount of power supply current is very useful for line safety.

In general, only the capacitor added to the power grid under all load conditions is removed, and the current flowing at this time is taken as the standard current value to add the voltage across the load to meet the voltage demand of the consumer under all load conditions. The electric current required by the power of the electric appliance is determined, and this current conforms to the lower limit value of the allowed change of the circuit current. Under such conditions, the capacitance value of the capacitor is selected to constitute the quasi-constant current device of the present invention.

The curve of the current versus load resistance in the quasi-constant current region is shown in Figure 3.

As can be seen from the above description, when the current changes within the allowable range, the voltage across the capacitor will only change within the same percentage. Therefore, if the positions of C / ^ and ¼ in the above description are exchanged, the two ends of the load The voltage change will be within the specified range, which will enter the quasi-constant voltage operating area. The lower limit value of the allowable voltage change is used as the voltage across the load when the load is switched on, and the capacitance value of the capacitor is selected by the loop current determined by the load power and the voltage across the capacitor, thereby forming the quasi-constant voltage device of the present invention. Judging from the circuit configuration, the device of the present invention is quasi-constant current and quasi-constant voltage.

The curve of load voltage versus load resistance in the quasi-constant voltage region is shown in Figure 4.

It is conceivable that the load resistance value of a quasi-constant current device of the present invention with a determined capacitance value continues to increase. This device will operate beyond the quasi-constant current area. At this time, the loop current does not meet the quasi-constant current and is less than the quasi-constant current value. When the voltage across the load reaches the lower limit of the allowed voltage change, the load resistance will be the starting point for entering the quasi-constant voltage zone. As long as the actual load current of the consumer is less than this value, the consumer can produce the same function as when used in the actual power grid. The difference is that the consumer is actually protected against short circuits.

The advantages of the device of the invention are −

1. Because one or more loads in series are allowed, each of these loads can be low-voltage, and for low-voltage electrical appliances, the transformer can be omitted and used directly in the utility power grid to reduce costs and eliminate the losses of the voltage-reducing device. In particular, the device of the present invention can be applied to appliances with different voltage levels in various countries.

2. Even if the load terminal is short-circuited, due to the limited current value, it will not cause the short-circuit consequences of general electrical appliances directly powered by the power grid. This safety function is particularly important in special occasions.

3. When power is supplied by the device of the present invention, the impact of surge current on the electrical appliances occurs at the instant of power-on, which prolongs the life of the electrical appliances. Most of the damage to loads such as filaments occur under the impact of the current at the instant of power-on.

4. The device of the present invention is free from harmonic pollution generated when other constant current or constant voltage devices work.

5. The device of the present invention has a capacitive impedance, which has a certain compensation effect on the power factor of the power grid, which is more in-situ compensation than the general method of in-situ compensation in residential quarters or large consumers.

6. Compared with the general constant current or constant voltage device, the device itself has extremely low losses, which can be ignored, so there is no heat generation, it is not easy to damage, it works reliably, and it is very light. 7. When the device of the present invention is used, no spark occurs when the load and cut load meet certain set conditions, which is very advantageous for places that require special attention to safety in coal mines and petrochemical industries. The huge explosion-proof explosion-proof devices can be completely omitted, saving investment. , Light use, safe and reliable.

8. All these advantages of the invention are obtained by extremely simple construction, which is a great advantage in itself. Overview of the drawings

FIG. 1 is a schematic diagram of a circuit configuration of the present invention;

Figures 2a and b are triangle vector diagrams of the circuit impedance and voltage when the device of the present invention is in a resistive load; Figure 3 is a graph of the relationship between load current and load resistance in a quasi-constant current region;

Figure 4 is the relationship between the load terminal voltage and load resistance in the quasi-constant voltage region.

5 is a schematic circuit diagram of a first embodiment of the present invention;

6 is a voltage vector diagram of the first embodiment;

7 is a schematic circuit diagram of a second embodiment of the present invention;

8 is a voltage vector diagram of the second embodiment;

Figures 9a, b are examples of capacitor combinations.

Examples

The device of the present invention will be described in detail through embodiments below with reference to the accompanying drawings, and the essence of the method of the present invention can be further understood from these descriptions.

FIG. 5 is a first embodiment of the present invention. It is an example of a quasi-constant current device. The load is composed of 8 load components connected in series, and each load component is a 12V Wn = 50W halogen lamp in parallel with a switch Kn. , N = l- & composition.

Allowable percentage change of given current ^, βι ^?-= Α ^ mains voltage ^ volt, frequency 5 Hz.

Under the condition that the load is completely removed (all switches κη are closed, and the load equivalent resistance R = 0), the current flowing in the circuit is a standard current value of 1 ~, then when f = 50H _z

U ^ = U _XC = I ( _C = IV2 π fC = I ~ / 314C With the load fully connected, the current in the loop is ~, at this time the voltage at the load end U ^ nWn / σ 1 ~, and the voltage across the capacitor is σ _{ϋ χσ}

= 0. 436X220 ^ 96V just meets the voltage requirements of 8 tungsten halogen lamps. U ~ nWn nWn Press σ I ~ = σ ― =

Xc U _R U ~ 1- σ ²

0.9 X 220X2 π X50C = 8X 50 / (220X0. 436) O8 X50 / (22 (f X0, 436X0. 9X 314) = 67X 1 (T ⁶ method The voltage triangle of the circuit in this example when all 8 lamps are connected See Figure 6. And Figure 3 is the curve of the current change when the load (number of lamp connections) changes, and the percentage of current change shown in Figure 3 is δ = 10%.

In this example, a capacitor of 67 microfarads can be used to provide a maximum of 8 12V 50W tungsten halogen lamps. By turning on the corresponding switch Kn, any number of lamps can be used (from one unused to a maximum of 8). The current change does not exceed 10%. However, in the case of the device of the present invention, when the power of more than 8 X 50 = 400 watts is used, the current will decrease by more than 10%. This is the watt-limiting function of the device of the present invention, which may appear on the network equipped with the device. Danger to the line caused by excessive capacity electricity.

In the design of the above example, since the current when all 8 lamps are connected is set to ^ / ~, this current is again quantified by the rated current of the lamp / ^ ¾ /. If the number of lamps connected is less than 8, the current will be Slight increase, that is, the current flowing in the running lamp will exceed the rated value calculated based on its power. In order to prevent any lamp from flowing current exceeding its rated value under any use conditions, the capacitance value can be selected. The value can be achieved at a slightly lower value than its real power. This is a common design technique, which is easy to understand and need not be described in detail.

The use case of this example has all the advantages mentioned earlier. Low-pressure tungsten halogen lamps originally have high light efficiency and long life, and have superior light-emitting characteristics than fluorescent lamps. There is no voltage-reducing device and the loss and failure probability caused by them. Therefore, it meets energy-saving and environmental protection requirements. It can be designed to have no sparks and no current impact when switching on and off. It is safe and long life. Short-circuiting any one lamp does not have dangerous consequences. Due to the low operating voltage of the load, it is also superior in terms of protection against electric shock.

Fig. 7 is a second embodiment of the present invention, and shows an example in which a television set is operated as a load in a quasi-constant voltage region in the device of the present invention.

Let the TV set U _TV = 180, the allowable percentage of voltage change is 6 = 5%, σ = 1-δ = 0.95. Minimum voltage at load end U _TV = σ [; ~ = 0.95 X 220 = 209,

U _xr = 1- σ ² = 68. 7 Press I _TV X _C : Ιγγ / 2 fC II. 86/3140 = 68. 7 C = 40 microfarads This example shows the voltage triangle diagram when the TV is connected.

In this example, a capacitor of 40 microfarads is added according to the solution of the invention (:, adding a small cost so that the television is already under the condition of short circuit protection, which is achieved by the current limiting function of the device of the invention, even if the television A short circuit of the power supply will not cause an explosion accident, nor will it further burn other components, nor will it affect the safety of the power grid due to the failure of the TV set. Similarly, the device in this example has no impact on the current of the TV set when it is turned on. It has a significant effect on extending the life of the picture tube and related components.

The capacitor used in the device of the present invention may be a combination of a plurality of capacitors connected in series and parallel. Figures 9a and b are two examples, and a tap line can be drawn from each of the series and parallel nodes to obtain multiple terminals with multiple differences. The capacitance is adapted to a variety of quasi-constant current or quasi-constant voltage requirements, which are easily understood by those skilled in the art, and need not be described in detail.

Claims

Rights request

1. A method for controlling the power supply of AC appliances with quasi-constant current, characterized in that:

Connect a normally closed switch at both ends of an electrical consumer in parallel as a load component;

Connect at least one of the above-mentioned load components in series with each other, and then connect in series with a device having a capacitance C and then connect it to the grid end;

Connect or disconnect the corresponding electrical consumers from or to the power grid by opening or closing the normally closed switch of any one or several of the load components;

Select the capacitance value of the above capacitors so that the loop current of all load components when the normally closed switches are closed is the standard current value. When all the normally closed switches are open, the voltage across the load components in series meets the voltage requirements of the load, and the loop current is within the allowable range of variation. Lower limit.

2. A quasi-constant voltage control method for power supply of alternating current electrical appliances, characterized in that-a normally closed switch in parallel at both ends of an electrical appliance is used as a load component;

Connect or disconnect the corresponding electrical consumers from or to the power grid by opening or closing the normally closed switch of any one or several of the load components

Take the lower limit of the voltage allowable variation as the voltage across the load, determine the voltage across the capacitor based on the required loop current and the mains voltage, and select the capacitance value of the capacitor.

3. A quasi-constant current or quasi-constant voltage controlled AC power supply device, characterized by:

A normally closed switch is connected in parallel at both ends of an electrical appliance to form a load component. At least one of the above load components is connected in series with each other, and then is connected in series with a device having a capacitance C.

4. The device according to claim 3, characterized in that said capacitor device is formed by combining a plurality of capacitor devices in series and / or in parallel.

5. The device according to claim 4, characterized in that each connection point of the combined capacitive device can be led out to become an input or output terminal.

6. The device according to any one of claims 3-5, wherein the load is a low-pressure tungsten halogen lamp.