Insulation resistance detection circuit

Abstract

The utility model relates to an insulation resistance detection circuit which comprises at least two external resistance branches which are connected in parallel, each external resistance branch is composed of a resistor and a switch, one end of each external resistance branch is grounded, and the other end of each external resistance branch is connected with the positive electrode or the negative electrode of a direct-current power supply. According to the utility model, accurate detection of the insulation resistance can be realized only by adding sampling detection on one side of the DC power supply, and the insulation strength of the DC power supply system can not be changed.

Description

Technical Field

[0001] The utility model relates to the field of insulation resistance detection, and particularly to an insulation resistance detection circuit. Background Art

[0002] In a DC system insulation detection circuit, a balanced bridge and an unbalanced bridge are the most widely used insulation detection circuits. When the positive-to-ground resistance and the negative-to-ground resistance decrease equally or have similar values, even if the insulation resistance has dropped below the warning value, the balanced bridge cannot detect the insulation fault. The unbalanced bridge solves the inherent problems of the balanced bridge and has a relatively high accuracy in identifying the ground insulation resistance. However, due to the influence of the ground capacitance, the detection speed is very slow, that is, the identification speed is slow, and rapid protection cannot be achieved. Summary of the Utility Model

[0003] In order to solve the above problems, the utility model provides an insulation resistance detection circuit.

[0004] The utility model adopts the following technical scheme:

[0005] An insulation resistance detection circuit includes at least two externally added resistance branches connected in parallel with each other. Each externally added resistance branch consists of a resistor and a switch. One end of the externally added resistance branch is grounded, and the other end is connected to the positive or negative pole of a DC power supply.

[0006] Further, there are two externally added resistance branches, and the resistance values of the resistors in the two externally added resistance branches are both greater than or equal to 1 M.

[0007] Further, there are more than two externally added resistance branches. Among them, the resistance values of the resistors in two externally added resistance branches are greater than or equal to 1 M, and the resistance values of the resistors in other externally added resistance branches are less than 1 M and greater than 1 K.

[0008] By adopting the above technical scheme, the utility model can achieve accurate detection of the insulation resistance only by adding sampling detection on one side of the DC power supply, and can not change the insulation strength of the DC power supply system. Brief Description of the Drawings

[0009] Figure 1 The figure shows the circuit diagram for measuring the positive-to-ground detection voltage with only two branches in an embodiment of the utility model.

[0010] Figure 2 The figure shows the circuit diagram for measuring the positive-to-ground detection voltage with more than two branches in this embodiment.

[0011] Figure 3 The figure shows the circuit diagram for measuring the negative-to-ground detection voltage with only two branches in this embodiment. Detailed Description of the Invention

[0012] To further illustrate each embodiment, the present utility model provides accompanying drawings. These drawings are part of the disclosure of the present utility model, mainly used to illustrate the embodiments, and can be combined with the relevant descriptions in the specification to explain the operating principle of the embodiments. With reference to these contents, those of ordinary skill in the art should be able to understand other possible implementation manners and the advantages of the present utility model. The components in the drawings are not drawn to scale, and similar component symbols are usually used to represent similar components.

[0013] The present utility model will be further described below in conjunction with the accompanying drawings and specific implementation manners.

[0014] This embodiment discloses an insulation resistance detection circuit, which includes at least two externally added resistance branches connected in parallel. Each externally added resistance branch consists of a resistor and a switch. One end of the externally added resistance branch is grounded, and the other end is connected to the positive or negative pole of a DC power supply.

[0015] When the insulation resistance detection circuit is in use, the closing states of the switches in each externally added resistance branch can be arbitrarily combined. By adjusting the combined switching modes of the switches in all externally added resistance branches, the total resistance corresponding to all externally added resistance branches can be changed, and the voltage corresponding to the externally added resistance branches under each combined switching mode is measured; based on the voltage across the DC power supply and the voltage corresponding to the externally added resistance branches under different combined switching modes, the resistance values of the positive-to-ground insulation resistance and negative-to-ground insulation resistance of the DC power supply are calculated.

[0016] As Figure 1 shown, the DC power supply system includes two externally added resistance branches, and these two externally added resistance branches are connected to the positive pole of the DC power supply for testing the positive-to-ground voltage. Figure 1 In + , R - is the positive-to-ground insulation resistance, R + is the negative-to-ground insulation resistance, resistor R1 and switch S1 are the first externally added resistance branch, resistor R2 and switch S2 are the second externally added resistance branch, U + is the positive-to-ground detection voltage (i.e., the voltage corresponding to the externally added resistance branch), U - is the negative-to-ground detection voltage, U b is the DC power supply detection voltage. Looking at the whole system, when U b has been detected by default, only the detection of U + or U - is needed. The detection of voltage U + or U - can be achieved by measuring the voltage between the positive pole of the power supply and the metal shell.

[0017] In the case of only two additional resistance branches, the different combined switching modes of the two switches in the two additional resistance branches can be the following three cases, and each of the combined switching modes in these three cases includes two: Case 1: The first combined switching mode is that the switch in the first additional resistance branch is turned on and the switch in the second additional resistance branch is turned off; the second combined switching mode is that the switch in the first additional resistance branch is turned off and the switch in the second additional resistance branch is turned on. Case 2: The first combined switching mode is that the switch in the first additional resistance branch is turned on and the switch in the second additional resistance branch is turned off; the second combined switching mode is that the switches in both the first additional resistance branch and the second additional resistance branch are turned on. Case 3: The first combined switching mode is that the switch in the first additional resistance branch is turned off and the switch in the second additional resistance branch is turned on; the second combined switching mode is that the switches in both the first additional resistance branch and the second additional resistance branch are turned on.

[0018] The following is described with reference to Figure 1 , taking Case 1 as an example. Taking the detection of U + as an example, only closing S1, the detected voltage is U +1 ; only closing S2, the detected voltage is U +2 . Then the calculation formulas for the resistance values of the positive-to-ground insulation resistance and the negative-to-ground insulation resistance are derived through common circuit principles, as follows:

[0019]

[0020] When it belongs to Case 2 or Case 3, closing S1 and S2 simultaneously, the detected voltage is U +12 . Substituting U +12 into the above formula in place of U +1 or U +2 , the detected insulation resistance value can be verified again to correct the insulation resistance sampling accuracy. If U + is particularly abnormal (extremely large or extremely small), the machine can quickly respond and stop.

[0021] In addition, when the insulation resistance fails at one end, the voltage at this end is very small. If the voltage of this path is exactly detected, the error is very large and the detection accuracy is not high. If there is a single-end insulation fault according to the above judgment, the sampling conditioning circuit can be dynamically adjusted to achieve more accurate voltage detection. For example, when performing differential sampling, a part of the resistors can be short-circuited according to the above voltage switch to improve the insulation resistance sampling accuracy.

[0022] In addition to the above Figure 1 case of two additional resistance branches, this embodiment may also include three or more additional resistance branches, such as Figure 2As shown, by adding more external resistance branches at one end, the sampling becomes more flexible and adaptable. For example, when including three external resistance branches, seven voltage values can be sampled, and it only occupies one voltage sampling port. In specific use, appropriate external resistances can be designed to improve the sampling accuracy.

[0023] In the value selection of the resistors in the external resistance branches, in this embodiment, it is preferably set that when there are two external resistance branches, the resistance values of the resistors in both external resistance branches are greater than or equal to 1M; when there are more than two external resistance branches, the resistance values of the resistors in two of the external resistance branches are greater than or equal to 1M, and the resistance values of the resistors in the other external resistance branches are less than 1M and greater than 1K.

[0024] In addition, in the above examples, the external resistance branches are all connected to the positive pole of the DC power supply. In use, the external resistance branches can also be connected to the negative pole of the DC power supply to sample U - , such as Figure 3 shown.

[0025] This embodiment uses adding external resistance branches at one end to achieve system insulation detection, switches different switches to change the resistance value, and detects the sampling voltage under different resistance values, so as to calculate the insulation resistance of the positive and negative ends of the system to the ground.

[0026] Although the present invention is specifically shown and described in combination with the preferred implementation embodiments, those skilled in the art should understand that various changes can be made to the present invention in terms of form and details without departing from the spirit and scope of the present invention defined by the appended claims, and all of them are within the protection scope of the present invention.

Claims

1. An insulation resistance detection circuit, characterized in that, It includes at least two externally added resistance branches connected in parallel with each other. Each externally added resistance branch consists of a resistor and a switch. One end of the externally added resistance branch is grounded, and the other end is connected to the positive or negative pole of a DC power supply.

2. The insulation resistance detection circuit according to claim 1, wherein: There are two externally added resistance branches, and the resistance values of the resistors in both externally added resistance branches are greater than or equal to 1 MΩ.

3. The insulation resistance detection circuit according to claim 1, wherein: There are more than two externally added resistance branches. Among them, the resistance values of the resistors in two externally added resistance branches are greater than or equal to 1 MΩ, and the resistance values of the resistors in other externally added resistance branches are less than 1 MΩ and greater than 1 kΩ.

Images