A device for preventing excessive low-temperature starting current of a direct-current PTC heater

Abstract

The utility model discloses a device that prevents the low temperature starting current of DC PTC heater too big, including strong electricity part, control part, precharge capacitor C1 is parallelly connected with PTC heater EH1 in strong electricity part and forms parallel circuit, and one electrode of power supply is connected to one end of parallel circuit, and the other electrode of power supply is connected through the first controllable switch of parallel, the second controllable switch of parallel to the other end of parallel circuit, and the second controllable switch has the series branch that precharge resistance R1 is connected in series and constitutes, and control part controls the switching of the first controllable switch, the second controllable switch and conduction. The utility model can reduce the starting current when PTC low temperature starts, and reduce the impact to the power grid.

Description

Technical Field

[0001] This utility model relates to the field of PTC heater starting devices, specifically a device to prevent excessive low-temperature starting current of DC PTC heaters. Background Technology

[0002] Currently, the heaters in existing air conditioning equipment generally use electric heating tubes to heat the evaporator for defrosting and other purposes. While these heaters offer good heating performance, their surfaces glow red during operation, posing a risk of burns and fires. PTC heaters, on the other hand, have advantages such as low thermal resistance and high heat exchange efficiency. They are automatic temperature-controlled, energy-saving electric heaters, and their outstanding feature is their safety performance; they do not exhibit the red-glowing phenomenon seen with electric heating tubes under any application conditions. Due to these advantages, PTC heaters have widely replaced electric heating tubes in air conditioning equipment. However, because the refrigeration components of an air conditioner (such as the evaporator) operate at low temperatures, PTC heaters may experience excessive starting current when starting at low temperatures. Utility Model Content

[0003] This invention provides a device to prevent excessive starting current of DC PTC heaters at low temperatures, thereby solving the problem of excessive starting current in existing air conditioning PTC heaters when operating at low temperatures.

[0004] To achieve the above objectives, the technical solution adopted by this utility model is as follows: A device for preventing excessive low-temperature starting current of a DC PTC heater includes a high-voltage section and a control section. The high-voltage section includes a pre-charge capacitor C1, which is connected in parallel with the PTC heater EH1 to form a parallel circuit. One end of the parallel circuit is connected to one electrode of the power supply, and the other end of the parallel circuit is connected to the other electrode of the power supply through a first controllable switch. The first controllable switch is connected in parallel with a series branch consisting of a second controllable switch and a pre-charge resistor R1 connected in series. The control section controls the first controllable switch and the second controllable switch to switch on and off.

[0005] Furthermore, the control section includes a precharge relay KA1, a time-delayed conduction relay KT1, and a working relay KA2. One end of the coil of the precharge relay KA1, one end of the coil of the time-delayed conduction relay KT1, and one end of the coil of the working relay KA2 are all connected to ground. The other end of the coil of the precharge relay KA1 and the other end of the coil of the time-delayed conduction relay KT1 are all connected to and connected to the control voltage signal through the normally closed contact KA2-1 of the working relay KA2. The other end of the working relay KA2 is connected to the control voltage signal through the normally open contact KT1-1 of the time-delayed conduction relay KT1. Furthermore, the normally open contact KT1-1 of the time-delayed conduction relay KT1 is connected in parallel with a normally open contact KA2-2 of the working relay KA2. In the high-voltage section, the first controllable switch is another normally open contact KA2-3 of the working relay KA2, and the second controllable switch is the normally open contact KA1-1 of the precharge relay KA1. The normally open contact KA2-3 and normally open contact KA1-1 in the high-voltage section are switched on by the control section.

[0006] Furthermore, the first controllable switch connected to the other end of the parallel circuit is connected to another electrode of the power supply via fuse FU1.

[0007] The startup process of the PTC heater in this invention includes a pre-charge process and a normal operation process. During the pre-charge process, when the heating signal is first activated, the control voltage signal supplies power to the coils of the pre-charge relay and the time-delay relay through the normally closed contact of the working relay. The pre-charge relay activates, and the time-delay relay begins timing. Power is supplied to the PTC heater and the pre-charge capacitor through the contacts of the pre-charge relay and the pre-charge resistor, and the voltage and current of the PTC heater increase synchronously and slowly.

[0008] During normal operation, when the set time of the delayed conduction relay is reached, the delayed conduction relay is activated, the coil of the working relay is energized, and the precharge relay is disconnected. The device switches to normal operation, and the power supply is supplied to the PTC heater and the precharge capacitor through the contacts of the working relay.

[0009] The beneficial effects of this utility model are: 1. It can reduce the starting current of PTC at low temperatures, thus reducing the impact on the power grid.

[0010] 2. Improve the ripple quality of PTC during operation and reduce voltage fluctuations.

[0011] 3. The existing heating system can be directly modified by adding components.

[0012] 4. The circuit is protected by a fuse that blows when the PTC heater current exceeds a certain value. Attached Figure Description

[0013] Figure 1 This is a circuit schematic diagram of an embodiment of the present invention. Detailed Implementation

[0014] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0015] like Figure 1 As shown, this embodiment discloses a device for preventing excessive low-temperature starting current of a DC PTC heater, used to control the starting of the PTC, including a high-voltage part and a control part.

[0016] The control section includes a precharge relay KA1, a time-delay relay KT1, and a working relay KA2. One end of the coil of the precharge relay KA1, one end of the coil of the time-delay relay KT1, and one end of the coil of the working relay KA2 are all connected to ground GND. The other end of the coils of the precharge relay KA1 and the other end of the coil of the time-delay relay KT1 are connected together and then connected to the control voltage signal through the normally closed contact KA2-1 of the working relay KA2. The other end of the working relay KA2 is connected to the control voltage signal through the normally open contact KT1-1 of the time-delay relay KT1. Furthermore, the normally open contact KT1-1 of the time-delay relay KT1 is connected in parallel with one normally open contact KA2-2 of the working relay KA2.

[0017] The high-voltage section includes a pre-charge capacitor C1, which is connected in parallel with the PTC heater EH1 to form a parallel circuit. One end of the parallel circuit is connected to the positive terminal of the DC power supply, and the other end of the parallel circuit is connected to the negative terminal of the DC power supply through another normally open contact KA2-3 of the working relay KA2 and the fuse FU1 in sequence. The normally open contact KA2-3 is connected in parallel with a series branch consisting of a pre-charge resistor R1 and the normally open contact KA1-1 of the pre-charge relay KA1.

[0018] The first controllable switch is the normally open contact KA2-3 of the working relay KA2, and the second controllable switch is the normally open contact KA1-1 of the pre-charge relay KA1. The control unit first controls the normally open contact KA1-1 to conduct to achieve pre-charging, and then controls the normally open contact KA1-1 to open and the normally open contact KA2-3 to conduct to achieve normal operation. Thus, the control unit controls the switching of the first and second controllable switches to achieve the transition from pre-charging to normal operation. During startup, power is supplied to the PTC heater and pre-charge capacitor through the pre-charge resistor. Due to the capacitor's characteristics, the voltage across the PTC heater increases slowly. After a set time, the power supply switches to normal operation, thereby reducing the starting current of the PTC heater.

[0019] The specific working process of this embodiment is as follows: 1): Pre-flush process After the unit receives the heating control voltage signal, the control section supplies power to the coil of the precharge relay KA1 and the coil of the time-delay relay KT1 through the normally closed contact KA2-1 of the working relay KA2. The normally open contact KA1-1 of the precharge relay KA1 is turned on, and the time-delay relay KT1 starts timing at the same time.

[0020] In the high-voltage section, because the normally open contact KA1-1 of the pre-charge relay KA1 is conducting, the DC power supply powers the pre-charge capacitor C1 and the PTC heater EH1 through the fuse FU1, the normally open contact KA1-1 of the pre-charge relay KA1, and the pre-charge resistor R1. Due to the characteristics of capacitance, the voltage across the pre-charge capacitor C1 and the PTC heater EH1 will not change abruptly, but will slowly rise from 0V. Since current I=U / R, under the same resistance value, a decrease in voltage corresponds to a decrease in starting current. At the same time, as the PTC heater EH1 begins to operate, the surface temperature of the PTC heater rises, and its resistance changes accordingly.

[0021] 2): Normal working process During the pre-charge process, the coil of the time-delay relay KT1 is energized, and the time-delay relay KT1 begins timing, simultaneously initiating the pre-charge process. When the timing of the time-delay relay KT1 reaches the set value, its normally open contact KT1-1 closes, supplying power to the coil of the working relay KA2. When the working relay KA2 is energized, its normally closed contact K2-1 opens, and its normally open contacts KA2-2 and KA2-3 close. At this time, the power supply from the heating control voltage signal to the coils of the pre-charge relay KA1 and the time-delay relay KT1 is disconnected. The normally open contact KA1-1 of the pre-charge relay KA1 opens again, and the normally open contact KT1-1 of the time-delay relay KT1 also opens. The heating control voltage signal then energizes the working relay KA2 through its normally open contact KA2-2.

[0022] In the high-voltage section, since the normally open contact KA2-3 of the working relay KA2 is closed and the normally open contact KA1-1 of the precharge relay KA1 is open, the DC power supply is only supplied to the PTC heater EH1 and the precharge capacitor C1 through the normally open contact KA2-3 of the working relay KA2 and the fuse FU1. The unit enters the normal operating state. Due to the characteristics of the capacitor storage tank, the impact of grid voltage fluctuations on the PTC heater EH1 can be effectively reduced during operation.

[0023] The preferred embodiments of this utility model have been described in detail above with reference to the accompanying drawings. These embodiments are merely descriptions of preferred embodiments and are not intended to limit the concept and scope of this utility model. The various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. Such combinations, as long as they do not violate the spirit of this utility model, should also be considered as part of this disclosure. To avoid unnecessary repetition, this utility model will not further describe all possible combinations.

[0024] This utility model is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this utility model and without departing from the design idea of ​​this utility model, all modifications and improvements made by those skilled in the art to the technical solution of this utility model should fall within the protection scope of this utility model. The technical content for which protection is sought in this utility model has been fully recorded in the claims.

Claims

1. A device for preventing excessive low-temperature starting current of a DC PTC heater, characterized in that, It includes a high-voltage section and a control section. The high-voltage section includes a pre-charge capacitor C1, which is connected in parallel with the PTC heater EH1 to form a parallel circuit. One end of the parallel circuit is connected to one electrode of the power supply, and the other end of the parallel circuit is connected to the other electrode of the power supply through a first controllable switch. The first controllable switch is connected in parallel with a series branch consisting of a second controllable switch and a pre-charge resistor R1 connected in series. The control section controls the first controllable switch and the second controllable switch to switch on and off.

2. The device for preventing excessive low-temperature starting current of a DC PTC heater according to claim 1, characterized in that, The control section includes a precharge relay KA1, a time-delay relay KT1, and a working relay KA2. One end of the coil of the precharge relay KA1, one end of the coil of the time-delay relay KT1, and one end of the coil of the working relay KA2 are all connected to ground. The other end of the coil of the precharge relay KA1 and the other end of the coil of the time-delay relay KT1 are all connected to and connected to the control voltage signal through the normally closed contact KA2-1 of the working relay KA2. The other end of the working relay KA2 is connected to the control voltage signal through the normally open contact KT1-1 of the time-delay relay KT1. Furthermore, the normally open contact KT1-1 of the time-delay relay KT1 is connected in parallel with a normally open contact KA2-2 of the working relay KA2. In the high-voltage section, the first controllable switch is another normally open contact KA2-3 of the working relay KA2, and the second controllable switch is the normally open contact KA1-1 of the precharge relay KA1. The normally open contact KA2-3 and normally open contact KA1-1 in the high-voltage section are switched on by the control section.

3. A device for preventing excessive low-temperature starting current of a DC PTC heater according to claim 1 or 2, characterized in that, The other end of the parallel circuit is connected to the first controllable switch, which is connected to the other electrode of the power supply via fuse FU1.

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