PTCR thermal resistor breakdown voltage test circuit and device
By adding a small current secondary air opening in the secondary circuit of the PTCR thermistor test circuit, the problem of PTCR thermistor breakdown and burning in the test circuit is solved, and the reliability and protection effect of voltage testing are achieved.
Patent Information
- Application Number
- CN202422168866.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-04
- Publication Date
- 2025-07-25
- Estimated Expiration
- 2034-09-04
AI Technical Summary
In the existing PTCR thermistor breakdown voltage test line, when the primary coil current reaches the empty opening level, the secondary PTCR thermistor may have been broken down and burned.
Add a small current secondary air opening to the secondary circuit of the test circuit as a protection device. By gradually increasing the voltage value, ensure that the current does not exceed the current limit value of the secondary air opening until the secondary air opening acts to protect the test fixtures and other devices.
It realizes timely protection of PTCR thermistor, avoids damage to the test fixtures and other devices, and accurately judges the breakdown voltage.
Smart Images
Figure CN223155137U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of thermistor testing, and more specifically, to a breakdown voltage testing circuit and device for a PTCR thermistor. Background Art
[0002] The withstand voltage of a PTCR thermistor is one of the very important parameters of the PTCR thermistor, and this parameter needs to be tested during both the design and manufacturing stages. Figure 1 It is the schematic diagram of the traditional breakdown voltage testing circuit for a PTCR thermistor. A 220V AC power supply is connected in series with a 10A air switch, and then connected to the primary of an autotransformer. The secondary of the autotransformer is connected to the primary of a step-up transformer, and the secondary is directly connected to the PTC thermistor to be tested. During use, when the PTCR thermistor is broken down, the protection current in the primary coil is relatively large, and it cannot respond in time to the increase in current in the load, resulting in a large increase in the current of the PTCR thermistor to be tested before the current in the primary coil reaches the action level of the air switch. At this time, the tested PTCR thermistor may have been short-circuited and burned out the installation fixture of the PTCR thermistor. Sometimes, even though the short-circuit current does not reach the protection current (10A) of the air switch, the tested PTCR thermistor has been broken down, leading to dangerous situations such as open flames.
[0003] Therefore, the present application provides a breakdown voltage testing circuit and device for a PTCR thermistor to solve the above problems. Summary of the Utility Model
[0004] The technical problem to be solved by the present application is that in the existing breakdown voltage testing circuit of a PTCR thermistor, when the current in the primary coil reaches the air switch level, the secondary PTCR thermistor may have been broken down and burned out. The purpose is to provide a breakdown voltage testing circuit and device for a PTCR thermistor, which can achieve timely protection of the PTCR thermistor by improving the secondary circuit of the testing circuit.
[0005] The present application first provides a breakdown voltage testing circuit for a PTCR thermistor, including: a primary air switch, an autotransformer, a step-up transformer, and a secondary air switch; one end of the primary air switch is connected to an AC power supply, the other end is connected to the primary of the autotransformer, the secondary of the autotransformer is connected to the input of the step-up transformer, the output of the step-up transformer is connected to the secondary air switch, and the secondary air switch is used to connect a testing fixture; wherein, the air switch current value of the primary air switch is greater than the air switch current value of the secondary air switch.
[0006] With the above technical solution, by adding a secondary miniature circuit breaker with a small current in the secondary circuit of the test circuit as a protection device, when testing, the voltage value is slowly increased from low voltage, and the current in the circuit will not exceed the current limit value of the secondary miniature circuit breaker. Finally, when approaching the failure state of the PTCR thermistor, the current in the circuit will gradually increase. When the current reaches the current value of the secondary miniature circuit breaker, the secondary miniature circuit breaker trips, achieving the test purpose while effectively protecting the test fixture and other devices in the circuit.
[0007] Further, it also includes: a voltage transformer, a digital AC voltmeter, a sampling resistor, and a digital millivoltmeter; the output of the step-up transformer is connected to the voltage transformer, and the voltage transformer is connected to the digital AC voltmeter; the secondary miniature circuit breaker is connected to the test fixture through the sampling resistor, and both ends of the sampling resistor are connected to the digital millivoltmeter.
[0008] Further, the circuit breaker current value of the primary miniature circuit breaker is 10A, and the circuit breaker current value of the secondary miniature circuit breaker is 1A.
[0009] Further, the AC power supply uses a 220V AC power supply.
[0010] Further, the autotransformer uses a 2KVA, 250V autotransformer.
[0011] Further, the step-up transformer uses a transformer with a fixed output ratio of 1:7 and a power of 2KVA.
[0012] Further, the voltage transformer uses a 10:1 voltage transformer.
[0013] Further, the sampling resistor uses a 1-ohm fixed resistor.
[0014] This application also provides a PTCR thermistor breakdown voltage test device, including: a box structure with at least three layers. The bottom layer of the box structure is used to place the AC power supply, the middle layer is used to place the test fixture and the PTCR thermistor to be tested, and the top layer is used to place a PTCR thermistor breakdown voltage test circuit as described above.
[0015] Further, the box structure is encapsulated with a fiberglass board.
[0016] Compared with the prior art, this application has the following beneficial effects: The present utility model adds a 1A small-current secondary miniature circuit breaker in the PTCR thermistor circuit, which is connected in series with the PTCR thermistor to be tested; the test voltage is gradually increased from low voltage to high voltage. When the PTCR thermistor enters the fast failure state under high voltage, the current flowing through the PTCR thermistor gradually increases. When it reaches the circuit breaker current value of the secondary miniature circuit breaker, the secondary miniature circuit breaker operates, achieving the dual purposes of judging the withstand voltage and protection. Brief Description of the Drawings
[0017] The drawings described herein are used to provide a further understanding of the embodiments of the present utility model, form a part of this application, and do not limit the embodiments of this application. In the drawings:
[0018] Figure 1 is a schematic circuit diagram of an existing breakdown voltage test circuit for a PTCR thermistor.
[0019] Figure 2 is a schematic circuit diagram of a breakdown voltage test circuit for a PTCR thermistor;
[0020] Figure 3 is a schematic structural diagram of a breakdown voltage test device for a PTCR thermistor. Detailed Embodiments
[0021] To make the objectives, technical solutions, and advantages of the present utility model clearer and more understandable, the present utility model will be further described in detail below in combination with embodiments and drawings. The illustrative embodiments and descriptions thereof of the present utility model are only used to explain the present utility model and do not limit the present utility model.
[0022] Embodiment 1
[0023] This Embodiment 1 provides a breakdown voltage test circuit for a PTCR thermistor, as Figure 2 shown. It includes: a primary air switch, an autotransformer, a step-up transformer, and a secondary air switch; one end of the primary air switch is connected to an AC power supply, the other end is connected to the primary of the autotransformer, the secondary of the autotransformer is connected to the input of the step-up transformer, the output of the step-up transformer is connected to the secondary air switch, and the secondary air switch is used to connect a test fixture; wherein, the rated current value of the primary air switch is greater than the rated current value of the secondary air switch.
[0024] During the test, first install the PTCR thermistor on the test fixture and confirm that the autotransformer is adjusted to the state of minimum output (0V voltage). First turn on the primary air switch, then turn on the secondary air switch, and gradually increase the input voltage of the autotransformer. The voltage step value and hold time can be set arbitrarily according to the test requirements to perform the breakdown voltage test of the PTCR thermistor.
[0025] The improvement of this solution is that a secondary air switch with a small current is added as a protection device in the secondary circuit of the test circuit. During the test, the voltage value is slowly increased from low voltage, and the current in the circuit will not exceed the current limit value of the secondary air switch. Finally, when it is about to reach the failure state of the PTCR thermistor, the current in the circuit will gradually increase. When the current reaches the rated current value of the secondary air switch, the secondary air switch disconnects, achieving the test purpose while effectively protecting the test fixture and other devices in the circuit.
[0026] Further, it also includes: a voltage transformer, a digital AC voltmeter, a sampling resistor, and a digital millivoltmeter; the output of the step-up transformer is connected to the voltage transformer, and the voltage transformer is connected to the digital AC voltmeter; the secondary switch is connected to the test fixture through the sampling resistor, and both ends of the sampling resistor are connected to the digital millivoltmeter.
[0027] Specifically, the output terminal of the step-up transformer is connected to the digital AC voltmeter through the voltage transformer, and the digital AC voltmeter displays the voltage value applied to the PTCR thermistor. The digital millivoltmeter is connected through the sampling resistor to display the voltage value across the sampling resistor. The sampling resistor uses a small-value resistor, and the current value flowing through the PTCR thermistor can be calculated. Based on the voltage value applied to the PTCR thermistor and the current value flowing through the PTCR thermistor, the power consumption of the PTCR thermistor can be calculated.
[0028] Further, the open-circuit current value of the primary switch is 10A, and the open-circuit current value of the secondary switch is 1A.
[0029] Further, the AC power supply uses a 220V AC power supply.
[0030] Further, the autotransformer uses an autotransformer with 2KVA and 250V.
[0031] Further, the step-up transformer uses a transformer with a fixed output ratio of 1:7 and a power of 2KVA.
[0032] Further, the voltage transformer uses a voltage transformer with a ratio of 10:1.
[0033] Further, the sampling resistor uses a fixed resistor of 1 ohm.
[0034] Specifically, the autotransformer and the step-up transformer jointly form the high voltage for testing. The primary of the autotransformer with the specifications of 2KVA and 250V is connected to the 220V AC power supply through the 10A primary switch, and the secondary of the autotransformer is connected to the 1A secondary switch as a protection device through the step-up transformer with a fixed output ratio (step-up ratio) of 1:7 and a power of 2KVA. At the output terminal of the step-up transformer, a digital AC voltmeter is connected through a 10:1 voltage transformer to display the voltage value applied to the PTCR thermistor. The secondary switch is connected in series with a 1-ohm (power 10W) sampling resistor and then connected to the test fixture. Both ends of the 1-ohm sampling resistor are connected to the digital millivoltmeter to display the voltage value across the 1-ohm sampling resistor. Through the readings of the digital AC voltmeter and the digital millivoltmeter, the power consumption of the PTCR thermistor can be calculated.
[0035] It can be understood that during testing, the primary air switch is closed first, and then the secondary air switch is closed, which can ensure that the initial large current when the primary air switch is closed will not cause the secondary air switch to trip immediately for protection. When the PTCR thermistor is facing breakdown and the current increases, the secondary air switch will first take protective action. This circuit can ensure the reliable progress of the breakdown voltage test, can also judge whether the PTCR thermistor is in a failure state according to the digital millivoltmeter, and can also protect the test fixture from being burned.
[0036] Embodiment 2
[0037] Embodiment 2 of the present invention provides a PTCR thermistor breakdown voltage test device as Figure 3 shown. It includes: a box structure with at least three layers. The bottom layer of the box structure is used to place the AC power supply, the middle layer is used to place the test fixture and the PTCR thermistor to be tested, and the top layer is used to place a PTCR thermistor breakdown voltage test circuit as described above.
[0038] Specifically, a box with a length of 650 * width of 650 * height of 1200 can be set. The box is divided into three layers. The bottom layer is the AC power supply placement area, the second layer is the area for placing the PTCR thermistor to be tested and the fixture, and the third layer is the breakdown voltage test circuit placement area.
[0039] Furthermore, the outer shell of the box can be encapsulated with fiberglass board to separate the test operator from the electrical part for protection purposes.
[0040] During testing, first install the sample to be tested on the test fixture, confirm that the autotransformer is adjusted to the state of minimum output (0V voltage), connect the primary air switch, then connect the secondary air switch, and gradually increase the input voltage of the autotransformer. Set the pressure step value and holding time according to the test requirements. Generally, according to a pressure gradient of every 50V, hold for 10 seconds after each pressure application, and then increase a voltage gradient until the protection action of the secondary air switch is completed. The voltage value that causes the secondary air switch to act is the withstand voltage of the PTCR thermistor. In addition, this device can measure the voltage value across the 1-ohm sampling resistor in the secondary circuit at a certain voltage, and then calculate the current value flowing back in the PTCR thermistor at this voltage, that is, the residual current or steady-state current. Multiply this current value by the applied voltage value to obtain the power consumption of the PTCR thermistor.
[0041] It can be understood that a small current secondary air switch of 1A is added to the PTCR thermistor circuit of the present utility model and is connected in series with the PTCR thermistor to be tested. The test voltage is gradually increased from low voltage to high voltage, and no large current appears during this process, nor will it cause the operation of the secondary air switch. However, when the PTCR thermistor enters the fast failure state under high voltage, the current flowing through the PTCR thermistor will gradually increase. This increase in current is a gradual process. When the current reaches the air switch current value of the secondary air switch, the secondary air switch operates, achieving the dual purposes of judging the withstand voltage and protection.
[0042] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present utility model. It should be understood that the above description is only the specific embodiments of the present utility model and is not used to limit the protection scope of the present utility model. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present utility model shall be included in the protection scope of the present utility model.
Claims
1. A breakdown voltage test circuit for a PTCR thermistor, characterized in that, Comprising: Primary air switch, autotransformer, step-up transformer and secondary air switch; One end of the primary air switch is connected to the AC power supply, the other end is connected to the primary of the autotransformer, the secondary of the autotransformer is connected to the input of the step-up transformer, the output of the step-up transformer is connected to the secondary air switch, and the secondary air switch is used to connect the test fixture; Wherein, the rated current value of the primary air switch is greater than the rated current value of the secondary air switch.
2. The breakdown voltage test circuit of a PTCR thermistor according to claim 1, characterized in that, Also comprising: Voltage transformer, digital AC voltmeter, sampling resistor and digital millivoltmeter; The output of the step-up transformer is connected to the voltage transformer, and the voltage transformer is connected to the digital AC voltmeter; The secondary air switch is connected to the test fixture through the sampling resistor, and both ends of the sampling resistor are connected to the digital millivoltmeter.
3. The breakdown voltage test circuit of a PTCR thermistor according to claim 1, wherein, The rated current value of the primary air switch is 10A, and the rated current value of the secondary air switch is 1A.
4. The breakdown voltage test circuit of a PTCR thermistor according to claim 1, characterized in that, The AC power supply uses a 220V AC power supply.
5. A breakdown voltage test circuit for a PTCR thermistor according to claim 1, characterized in that, The autotransformer uses a 2KVA, 250V autotransformer.
6. The breakdown voltage test circuit of a PTCR thermistor according to claim 1, characterized in that, The step-up transformer uses a transformer with a fixed output ratio of 1:7 and a power of 2KVA.
7. A breakdown voltage test circuit for a PTCR thermistor according to claim 2, characterized in that, The voltage transformer uses a 10:1 voltage transformer.
8. A breakdown voltage test circuit for a PTCR thermistor according to claim 2, characterized in that, The sampling resistor uses a 1-ohm fixed resistor.
9. A breakdown voltage testing device for a PTCR thermistor, characterized in that, Comprising: A box structure with at least three layers. The bottom layer of the box structure is used to place the AC power supply, the middle layer is used to place the test fixture and the PTCR thermistor to be tested, and the top layer is used to place a PTCR thermistor breakdown voltage test circuit as described in any one of claims 1-8.
10. A breakdown voltage testing device for a PTCR thermistor according to claim 9, characterized in that, The box structure is encapsulated with a fiberglass board.