CN104076207A - Electric vehicle insulation detecting circuit - Google Patents

Abstract

The invention discloses an electric vehicle insulation detecting circuit. By means of the characteristic that flexibility of a balanced bridge is high, by detecting electricity supply through an external low-voltage alternating power supply, on the premise that the whole vehicle system is not influenced, the insulation resistance value is accurately measured, operation and calculation are easy, and the insulativity of the electric vehicle is monitored in real time.

Description

A kind of electric motor car insulation detecting circuit

Technical field

The present invention relates to a kind of insulation detecting circuit, be specifically related to a kind of electric motor car insulation detecting circuit.

Technical background

Thereby electric motor car be take accumulator and is reached the object that electric motor car is travelled as driven by energy machine operation, conventional electric motor car driving power voltage is more than 36V, have up to 500V, rank considerably beyond safe voltage, therefore, the power system of electric vehicle need to have insulativity very reliably, to guarantee the normal operation of electric vehicle and user's safety.Good insulation properties can guarantee the safe operation of electrical equipment and circuit, and insulation resistance is the most basic insulation index of electrical equipment and electric wiring.

Therefore,, in order to detect in real time the insulating resistance value of electric motor car, monitoring electric motor car insulativity, has following solution: utilize high resistance measurement to carry out dividing potential drop measurement to leakage detecting circuit, thereby the insulation situation of battery is carried out to Real-Time Monitoring at present.This monitoring method needs the mutual closure of two switches to carry out measurement result and calculate insulating resistance value, and this method exists following shortcoming:

1, need to repeatedly disconnect, Closing Switch, complicated operation;

2,, along with Vehicle Driving Cycle, supply voltage can change, and test result is had to impact;

3, the dividing potential drop of test resistance affects the driving voltage of Full Vehicle System;

4, calculation of complex.

For overcoming the above problems, the present invention adopts new insulation detecting circuit, utilizes balanced bridge and uses external low-voltage alternating current power supply for electro-detection, guaranteeing not affect under the prerequisite of Full Vehicle System, accurately measures insulating resistance value, and operates, calculates simple.

Summary of the invention

The present invention, for overcoming deficiency of the prior art, utilizes external low-voltage alternating current power supply and balanced bridge to detect in real time insulating resistance value, guaranteeing not affect under the prerequisite of Full Vehicle System, accurately measures insulating resistance value.

For achieving the above object, technical scheme of the present invention is:

An electric motor car insulation detecting circuit, insulation one end, test side connects power supply u0 positive pole, resistance R 1 one end, resistance R 2 one end, the insulation test side other end contact resistance R1 other end, resistance R 3 one end, resistance R 5 one end; Resistance R 2 other ends are connected with resistance R 4 one end, resistance R 5 other ends; Resistance R 3 other ends and resistance R 4 other ends, power supply u0 negative pole, be connected; 5 liang of termination voltage collecting devices of resistance R.

Described power supply u0 is low-voltage alternating current power supply.

Between described insulation test side positive pole and described power supply u0 positive pole, resistance R 1, resistance R 2, add capacitor C isolated DC.

Described voltage collecting device adopts voltage isolation harvester.

Described resistance R 1=R2=R3=R4.

Compare existing insulation detecting circuit, the present invention has remarkable advantage and beneficial effect, is embodied as:

(1) use this insulation detecting circuit, owing to adopting external low-voltage alternating current power supply and balanced bridge to detect, measuring accuracy is high and car load driving power is not had to impact;

(2) use this insulation detecting circuit, owing to not using switch, operation, calculating are simply.

Accompanying drawing explanation

Fig. 1 is existing insulation detecting circuit figure;

Fig. 2 is insulation detecting circuit figure of the present invention.

Embodiment

Specific embodiment of the invention method is as follows:

A kind of electric motor car insulation detecting circuit, comprise insulation test side, power supply u0, capacitor C, resistance R 1, resistance R 2, resistance R 3, resistance R 4, resistance R 5, one end, described insulation test side connects capacitor C one end, the capacitor C other end connects power supply u0 positive pole, resistance R 1 one end, resistance R 2 one end, the insulation test side other end contact resistance R1 other end, resistance R 3 one end, resistance R 5 one end; Resistance R 2 other ends are connected with resistance R 4 one end, resistance R 5 other ends; Resistance R 3 other ends and resistance R 4 other ends, power supply u0 negative pole, be connected; 5 liang of termination voltage collecting devices of resistance R.

Described power supply u0 is low-voltage alternating current power supply, described resistance R 1=R2=R3=R4, and described voltage collecting device adopts voltage isolation harvester.

Existing method mostly is the method for switching over resistance, Fig. 1 is existing electric automobile insulation resistance detecting circuit figure, the measuring resistance that wherein resistance R C1, resistance R C2 are measuring known resistance, resistance R P, resistance R N are respectively the insulation equivalent resistance between positive and negative bus and casing.Principle of work is as follows: when switch S 1, S2 all disconnect, the voltage of measuring between positive and negative bus and casing is respectively UP1, UN1, can obtain:

$\frac{\mathrm{UP}1}{\mathrm{RP}}=\frac{\mathrm{UN}1}{\mathrm{RN}}---\left(1\right)$

When switch S 1 closure, S2 disconnect, between positive bus-bar and electric chassis, add measuring resistance RC1, the voltage of measuring between positive and negative bus and casing is respectively UP2, UN2, can obtain equally:

$\frac{\mathrm{UP}2}{\mathrm{RP}}+\frac{\mathrm{UP}2}{\mathrm{RC}1}=\frac{\mathrm{UN}2}{\mathrm{RN}}---\left(2\right)$

By equation (1), (2), combine and solve and can obtain:

$\mathrm{RP}=\mathrm{RC}1\×(\frac{\mathrm{UP}1\×\mathrm{UN}2}{\mathrm{UN}1\×\mathrm{UP}2}-1)$

$\mathrm{RN}=\mathrm{RC}1\×\left(\frac{\mathrm{UP}1\×\mathrm{UN}2-\mathrm{UN}1\×\mathrm{UP}2}{\mathrm{UP}1\×\mathrm{UP}2}\right)$

This method need to use switch closure, disconnect and measurement result repeatedly, combined calculation draws insulating resistance value, such calculation of complex, and need people for adding impedance, affect dielectric strength, before and after switch motion, cell voltage changes with automobile acceleration, deceleration meeting, larger on the impact of result.

Fig. 2 is insulation detecting circuit figure of the present invention, R1=R2=R3=R4 wherein, and resistance R 1, resistance R 2, resistance R 3, resistance R 4 form balanced bridges, RH is the equivalent resistance between anode and casing, when insulation is well resistance R H infinity, resistance R 5 both end voltage are zero, i.e. ui=0.When the insulativity between anode and casing reduces, RH changes, now AC signal can flow through capacitor C and equivalent resistance RH, the equivalent resistance at resistance R 1 two ends in electric bridge is reduced, its value is the in parallel value of resistance R 1 with RH, now bridge balance is broken, just have current flowing resistance R5, resistance R 5 two ends will produce pressure drop, pressure drop ui the process of using isolation to gather resistance R 5 two ends are calculated the size that can draw equivalent resistance RH, with this, carry out the insulativity between Real-Time Monitoring anode and casing, concrete computation process is as follows:

By balanced bridge, can be obtained: $\mathrm{ui}=(\frac{R3}{R1+R3}-\frac{R2}{R2+R4})\·u0$

Get in the present embodiment R1=R2=R3=R4=R, when insulativity between anode and casing is good, ui=0; When the insulativity between anode and casing reduces, R1 two ends resistance value is resistance R 1 and resistance R H resistance in parallel now $\mathrm{ui}=(\frac{R3}{R1\·\mathrm{RH}/(R1+\mathrm{RH})+R3}-\frac{R2}{R2+R4})\·u0$

Separate above-mentioned equation, draw:

By above-mentioned result of calculation, can be found out, this detection circuit operation and account form are simple, can effectively detect insulating resistance value.

Insulation detecting circuit of the present invention adopts and adds a low-voltage alternating current power supply, and between described AC power and battery, add capacitor C isolation, because battery is direct supply, therefore this low-voltage ac signal can not exert an influence to system, and battery can not interfere with testing circuit yet, this has just guaranteed that test result can not be subject to the impact of external interference.Balance electric bridge accuracy of detection is high, and detection, computing method are simple, easily calculate insulation equivalent resistance, is also convenient to monitoring, and testing circuit and circuit system are mutually to isolate, and have guaranteed like this accuracy of testing result.Use voltage isolation to gather resistance R 5 both end voltage, the isolation collection of guaranteeing resistance R 5 both end voltage can not exert an influence to testing circuit, further ensured the accuracy of the insulating resistance value detecting, certainly, this circuit also can be used for monitoring the device that other need to monitor insulativity, as between battery plus-negative plate, between positive and negative busbar etc.

For being one exemplary embodiment of the present invention; should be understood to is a certain demonstrative example wherein in the protection domain of claims of the present invention; there is the directiveness effect that those skilled in the art is realized to corresponding technical scheme, but not limitation of the invention.

Claims (5)

1. an electric motor car insulation detecting circuit, is characterized in that: insulation one end, test side connects power supply u0 positive pole, resistance R 1 one end, resistance R 2 one end, the insulation test side other end contact resistance R1 other end, resistance R 3 one end, resistance R 5 one end; Resistance R 2 other ends are connected with resistance R 4 one end, resistance R 5 other ends; Resistance R 3 other ends and resistance R 4 other ends, power supply u0 negative pole, be connected; 5 liang of termination voltage collecting devices of resistance R.

2. electric motor car insulation detecting circuit according to claim 1, is characterized in that: described power supply u0 is low-voltage alternating current power supply.

3. electric motor car insulation detecting circuit according to claim 2, is characterized in that: between described insulation test side positive pole and described power supply u0 positive pole, resistance R 1, resistance R 2, add capacitor C isolated DC.

4. electric motor car insulation detecting circuit according to claim 1, is characterized in that: described voltage collecting device is voltage isolation harvester.

5. according to the electric motor car insulation detecting circuit described in claim 3 or 4, it is characterized in that: described resistance R 1=R2=R3=R4.