Insulation detector and electric apparatus

Patent metadata

Field	Value
Publication number	US-2016377670-A1
Application number	US-201414902434-A
Country	US
Kind code	A1
Filing date	Oct 28, 2014
Priority date	Nov 22, 2013
Publication date	Dec 29, 2016
Grant date	—

Abstract

An insulation detector for highly accurately detecting or measuring, with a simple configuration, insulation resistance of a load or an apparatus to a ground or a housing and connected to an electric apparatus including one or both of an intra-apparatus capacitor and a battery, the insulation detector including an intra-insulation detector capacitor, a voltage detecting unit that detects a voltage of the intra-insulation detector capacitor, and a current-path forming switch for connecting the ground or the housing, the intra-apparatus capacitor, and the intra-insulation detector capacitor in series and forming a current path including insulation resistance of the electric apparatus. The insulation detector measures the insulation resistance by measuring a time constant of a change in the voltage of the intra-insulation detector capacitor. A capacitance value of the intra-insulation detector capacitor is a value negligible in the measurement of the insulation resistance compared with a capacitance value of the intra-apparatus capacitor.

First claim

1 . An insulation detector connected to an electric apparatus including an intra-apparatus capacitor, the insulation detector comprising:
an intra-insulation detector capacitor; a voltage detecting unit to detect a voltage of the intra-insulation detector capacitor; and a current-path forming switch to connect a ground or a housing, the intra-apparatus capacitor, and the intra-insulation detector capacitor in series and form a current path including insulation resistance of the electric apparatus, wherein the insulation detector measures the insulation resistance by measuring, with the voltage detecting unit, a time constant of a change in the voltage of the intra-insulation detector capacitor, and a capacitance value of the intra-insulation detector capacitor is a value negligible in the measurement of the insulation resistance compared with a capacitance value of the intra-apparatus capacitor.

2 . An insulation detector connected to an electric apparatus including a battery, the insulation detector comprising:
an intra-insulation detector capacitor; a voltage detecting unit to detect a voltage of the intra-insulation detector capacitor; and a current-path forming switch to connect a ground or a housing, the battery, and the intra-insulation detector capacitor in series and form a current path including insulation resistance of the electric apparatus, wherein the insulation detector measures the insulation resistance by measuring, with the voltage detecting unit, a time constant of a change in the voltage of the intra-insulation detector capacitor.

3 . The insulation detector according to claim 1 , wherein
the electric apparatus includes a configuration for driving a load with an inverter, and the insulation detector comprises a load-side path guide switch for connecting one end of the intra-apparatus capacitor and an output line to the load.

4 . The insulation detector according to claim 2 , wherein
the electric apparatus includes a configuration for driving a load with an inverter, and the insulation detector comprises a load-side path guide switch for connecting one pole of the battery and an output line to the load.

5 . The insulation detector according to claim 3 , wherein one of inverter elements in the inverter is also used as the load-side path guide switch.

6 . An insulation detector connected to an electric apparatus including an intra-apparatus capacitor, the insulation detector comprising:
an intra-insulation detector capacitor; a voltage detecting unit to detect voltages of the intra-apparatus capacitor and the intra-insulation detector capacitor connected in series; and a current-path forming switch to connect a ground or a housing, the intra-apparatus capacitor, and the intra-insulation detector capacitor in series and form a current path including insulation resistance of the electric apparatus, wherein the insulation detector measures the insulation resistance by measuring, with the voltage detecting unit, a time constant of a change in the voltage of the intra-insulation detector capacitor, and a capacitance value of the intra-insulation detector capacitor is a value negligible in the measurement of the insulation resistance compared with a capacitance value of the intra-apparatus capacitor.

7 . An insulation detector connected to an electric apparatus including a battery, the insulation detector comprising:
an intra-insulation detector capacitor; a voltage detecting unit to detect voltages of the battery and the intra-insulation detector capacitor connected in series; and a current-path forming switch to connect a ground or a housing, the battery, and the intra-insulation detector capacitor in series and form a current path including insulation resistance of the electric apparatus, wherein the insulation detector measures the insulation resistance by measuring, with the voltage detecting unit, a time constant of a change in the voltage of the intra-insulation detector capacitor.

8 . The insulation detector according to claim 6 , comprising discharge resistance connected to both ends of the intra-insulation detector capacitor.

9 . The insulation detector according to claim 6 , wherein
a switch for short circuit and a low resistance element having a resistance value lower than the insulation resistance connected in series are connected in parallel to the intra-insulation detector capacitor, and a resistance value of the low resistance element is a value for enabling, in measuring a time constant of the insulation resistance, the intra-insulation detector capacitor to be discharged in an interval of the measurement.

10 . The insulation detector according to claim 9 , wherein the insulation detector closes, when starting the measurement of the time constant, the current-path forming switch in a state in which the switch for short circuit is closed and opens the switch for short circuit after accumulation of charges in a stray capacitor.

11 . The insulation detector according to claim 1 , wherein the insulation detector calculates stray capacitance of a measurement system from a change in a voltage waveform immediately after a measurement start of the time constant and calculates a resistance value of the insulation resistance from a calculated value of the stray capacitance and a measured value of the time constant.

12 . The insulation detector according to claim 1 , wherein the intra-insulation detector capacitor has a configuration in which two capacitance elements are connected in parallel.

13 . The insulation detector according to claim 1 , wherein the voltage detecting unit includes a resistance element having a known resistance value smaller than an input of impedance of a measurement system of the voltage detecting unit, the resistance element being connected to an input of the measurement system in parallel.

14 . The insulation detector according to claim 1 , comprising a memory to record a detection value of the voltage detecting unit, wherein
the insulation detector can record a temporal change of the detection value.

15 . An insulation detector connected between one of a P bus and an N bus of an electric apparatus and an output line, the electric apparatus including a rectifier circuit that is disposed between an alternating-current power supply and a load and converts an alternating-current voltage from the alternating-current power supply into a direct-current voltage and an inverter that is connected to a post stage of the rectifier circuit and drives the load, and the output line connecting the inverter and the load, wherein
the insulation detector includes a resistor configured by a series-connected detection resistor and a voltage dividing resistor, a capacitor connected in parallel to the resistor, and a voltage detector to detect a resistance value of the measurement resistor, the voltage of which being divided by the voltage dividing resistor to measure a voltage value across both ends of the insulation detector, and the insulation detector detects insulation resistance between the load and a ground or a housing from the voltage value measured by the voltage detector.

16 . An insulation detector connected between one of a P bus and an N bus of an electric apparatus and an output line via a switch, the electric apparatus including a rectifier circuit that is disposed between an alternating-current power supply and a load and converts an alternating-current voltage from the alternating-current power supply into a direct-current voltage and an inverter that is connected to a post stage of the rectifier circuit and drives

Assignees

• Mitsubishi Electric Corp

Inventors

• Tamida Taichiro
• Uematsu Masayuki
• Tanabe Akira
• Hayashi Yoshitomo
• Tsutsumishita Yoji
• Tsujikawa Kosuke

Classifications

• G01R31/343

  in operation · CPC title

• G01R27/18

  Measuring resistance to earth {, i.e. line to ground} · CPC title

• G01R31/34

  Testing dynamo-electric machines · CPC title

• G01R27/025

  Measuring very high resistances, e.g. isolation resistances, i.e. megohm-meters · CPC title

• G01R31/12 Primary

  Testing dielectric strength or breakdown voltage {; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing (G01R31/08, G01R31/327 and G01R31/72 take precedence; measuring in plasmas G01R19/0061; measuring dielectric constants G01R27/2617; ESD, EMC or EMP testing of circuits G01R31/002)} · CPC title