GB2094486A

GB2094486A - Injection of simulating-noise signals

Info

Publication number: GB2094486A
Application number: GB8107101A
Authority: GB
Original assignee: Tohoku Metal Industries Ltd
Current assignee: Tokin Corp
Priority date: 1981-03-06
Filing date: 1981-03-06
Publication date: 1982-09-15
Also published as: GB2094486B

Abstract

A simulated-noise signal 3 is injected on the power line of the equipment under test without loss of AC power to the equipment, by a series resonance 4, 5 circuit having a resonance frequency equal to that of the AC power supply. The circuit is connected in the power line L1, L2 in series with the equipment 2, and a capacitor 6 is connected to the power line in parallel with the series resonance circuit and the equipment. Therefore, the simulated-noise signal 3 is injected on the power line through the capacitor at both ends of the resonance circuit, and AC power loss is prevented by use of the resonance circuit. A switching element 7 is used to short-circuit the resonance circuit for a period when the noise simulation is not carried out. Simulation of lightning strikes and ringing-surge due to turn-on or -off of other equipment is described.

Description

SPECIFICATION Injection of simulating-noise signals onto the power line This invention relates to noise simulators and, in particular, to injection of simulated-noise signals to the power line of the electric equipment under test and generators for generating simulating-noise signals such as a square wave for lightening strike simulation and a damped wave for ringing surge simulation.

Certain electric or electronic equipments such as data processors and others are sensitive to power-line noises such as voltage dips and highfrequency transients conducted through the power line, and are brought to mulfunction due to the power-line noises. In order to evaluate the sensitivity of equipments to power-line noises, noise simulators are used which make artificially power-line noises for feeding them to equipments under tests through their power lines.

Such a noise simulator is disclosed in "Noise simulators help find peril in power-line defects" described by Mr. M. L. Tandon in Electronics, March 7, 1966, pp. 117-121. In the noise simulator disclosed therein, power-line disturbances such as voltage dips and highfrequency transient noises are generated for simulation of electrical equipment against such noises.

Thereafter, it has been noted that low frequency surge noises such as lightening strikes and ringing surges also plague sensitive equipment such as data processors. Lightening strikes or surge noises due to thunders are conducted to equipment through the power line and may defeat or erroneously operate the equipment.

Ringing surges are low-frequency dampedwave noises due to turn-on or off of AC power to other electric devices having inductance or capacitance such as electric motors, transformers, phase-advance condensers and others.

For simulation of equipment against the lightening strikes and the ringing surges, noise simulators are desired to generate simulated lightening strikes and simulated ringing surges.

In noise simulators, a filter having an inductance coil and a capacitor is used in the power line of the equipment under test. AC power current always flows through the inductance coil to cause voltage drop. in a certain case, a transformer is used in place of the inductance coil to inject simulated-noise signals therethrough.

However, the use of transformer is not desired for injection of high-energy signals because a large transformer must be used.

It is an object of this invention to provide a noise simulator wherein simulated-noise signals are injected on the power line of equipment under test without cause of AC power loss and without use of transformer.

It is another object of this invention to provide a noise simulator wherein a square wave signal is generated and injected on the power line of equipment for lightening-strike simulation, without cause of AC power loss and without use of transformer.

It is still another object of this invention to provide a noise simulator wherein a dampedwave signal is generated and injected on the power line of equipment for ringing-surge simulation, without cause of AC power loss and without use of transformer.

It is yet another object of this invention to realize above mentioned objects with simple circuit formations and low cost.

According to this invention, a noise simulator has means for generating a simulated-noise signal. Series resonance means having a resonance frequency equal to a frequency of the AC power are connected in the AC power line in series with the equipment under test. Capacitor means are connected to the AC power line in parallel with the series resonance means and the equipment. The output of the signal generating means is connected across the series resonance means.

In the arrangement, the simulated-noise signal is fed to the equipment through the capacitor means and the power line. Since the series resonance means have a resonance frequency equal to the frequency of the AC power, voltage drop of AC power is not caused even the use of the noise simulator.

The series resonance means comprises inductance coil means and capacitor means.

Switching means may be connected across the series resonance means. When it is not required to inject simulated-noise signal on the power line, the switching means is turned on to short-circuit across the series resonance means.

For lightening-strike simulation, the simulatednoise generating means are a square-wave signal generator. It comprises DC power supply means.

First resistor means and capacitor means are connected to the DC power supply means in series with one another. A circuit branch including seriesly connected first switching means and second resistor means is connected across the capacitor means. Second switching means are connected at its one end to one end of the circuit branch.

Inductance coil means may be connected in the circuit branch in series with the first switching means and the second resistor means. Variable resistor means may be also used to be connected between the other end of the second switching means and the other end of the circuit branch.

In the arrangement, a square wave signal presents between the other end of the second switching means and the other end of the circuit branch by turning on the first switching means delayed after turning on the second switching means.

In another aspect of this invention, the simulated-noise generating means are a dampedwave signal generator for ringing-surge simulation. The damped-wave signal generator comprises DC power supply means and resistor means. A circuit branch including seriesly connected capacitor means and inductance coil means, is connected across the DC power supply means and the resistor means. Switching means is connected to one end of the circuit branch.

Variable resistor means may be connected between the other end of the switching means and the other end of the circuit branch.

In the arrangement of the damped-wave signal generator, the capacitor means are charged by the DC power supply means, and are discharged by turning off the switching means so that a damped-wave signal is injected on the power line.

Further objects, features and other aspects of this invention will be understood from the following description of preferred embodiments of this invention referring to the drawings annexed hereto.

Fig. 1 is a circuit diagram of a known circuit arrangement for injecting a simulated-noise signal onto the power line of a tested electric equipment; Fig. 2 is a circuit diagram of another known noise simulator; Fig. 3 is an embodiment of this invention for injecting a simulated-noise signal onto the power line of a tested electric equipment; Fig. 4 is a modification of the circuit arrangement of Fig. 3; Fig. 5 is a noise simulator of an embodiment according to this invention for lightening-strike simulation; Fig. 6 shows a waveform of a square-wave signal fed to the equipment in Fig. 5; Fig. 7 is a circuit diagram of a modified generator in Fig. 5; Fig. 8 is a circuit diagram of another modified square-wave signal generator; Fig. 9 is a circuit diagram of a further modification of the square-wave generator; Fig. 10 is a circuit diagram for generating a damped-wave signal;; Fig. 11 shows a waveform of a damped signal fed from the generator in Fig. 10 to the equipment; and Fig. 12 is a circuit diagram of a modified damped-wave signal generator.

Referring to Fig. 1, an AC power supply 1 is connected to an equipment 2. For noise simulation of equipment 1, a known noise simulator has a generator 3 for generating a simulated-noise signal. An inductance coil or a choke coil L is connected in power line 12 in parallel with equipment, and a capacitor C is connected between power lines i, and 12 to be in parallel with equipment 2 and inductance coil L.

The output of generator 3 is connected across inductance coil L.

In the arrangement, the signal from generator 3 3 is injected into lines 11 and 12 through capacitor C and fed to equipment 2. AC power is also fed to equipment through power lines 1 and 12. However, since AC power always flows through inductance coil L, voltage drop causes at inductance coil L.

in another known arrangement, a transformer Tis used in place of inductance coil L, as shown in Fig. 2. The output of generator 3 is coupled with the primary winding of transformer Tand the secondary winding of transformer Tis connected in series with equipment 2 in power line. The simulated noise is thus injected on the power line through the transformer.

In use of transformer for signal injection, a large transformer is disadvantageously required for injection of a high-energy signal.

Lightening strike due to thunder has a high voltage. Ringing surge due to turn-on or -off of inductive or capacitive electric devices is also high in energy.

Accordingly, the arrangement of Fig. 2 is not proper for injection of simulated lightening strikes or simulated ringing surges onto the power line of the equipment under test.

This invention provides arrangements adaptable for injection of high-energy signals onto the power line of the equipment without energy loss and without AC power loss.

Referring to Fig. 3, an embodiment of this invention has a series resonance circuit having a resonance frequency equal to a frequency of an AC power supply 1. Series resonance circuit includes an inductance coil 4 and a capacitor 5 and is seriesly connected in the power line 12 for feeding AC power from power supply 1 to an equipment 2. A capacitor 6 is connected between power lines 11 and i2 in parallel with equipment 2 and series resonance circuit 4-5.

A simulated-noise signal generator 3 is connected across series resonance circuit 4-5 to inject the noise signal at both sides T1 and T2 of the resonance circuit in the power line. The signal injected is fed to equipment 2 through capacitor 6 and power lines 11 and 12. AC power is also fed to equipment 2 through the series resonance circuit.

However, since the series resonance circuit has a resonance frequency equal to the frequency of the AC power, AC power is fed to equipment without any power loss at the resonance circuit.

A switching element 7 such as a mechanical switch or an electrical switching element may be connected in parallel with the resonance circuit 4-5 and across the resonance circuit 4-5, as shown in Fig. 4. When no simulated-noise signal is required to be injected onto the power line, switching element 7 is turned'on to short-circuit the resonance circuit 4-5. As a result, equipment 2 is directly connected to AC power supply 1 so that power loss is reliably removed.

For lightening-strike simulation, a square-wave signal generator 3' is used as simulated-noise signal generator 3 in Fig. 3 or 4, as shown in Fig.

5.

Referring to Fig. 5, a resistor 12 and a capacitor 13 are connected to a DC power supply 11 in series with one another. Switching element 14 and a resistor 1 5 are seriesly connected across capacitor 13. Another switching element 16 is connected between an output terminal T1 and a common connection point between resistor 2 and capacitor 3. The other end of capacitor 3 is connected to the other output terminal T2. The output terminals Tt and T2 are connected to both sides T and T2 of the series resonance circuit 4- Sin the power line 12, similar to in Fig. 3 or 4, so that the generated square wave may be injected on the power line.

In the arrangement, capacitor 13 is charged by DC power supply through resistor 12. When switching element 16 is turned on, a discharge current of capacitor 13 is fed to the power line from output terminals T1 and T2 through switching element 16. Thereafter when switching element is turned on, the residual charge of capacitor 13 is discharged through resistor 1 5, so that feed of the discharge current to the power line is stopped.

Accordingly, a square-wave signal is injected on the power line and lightening-strike simulation of the equipment can be performed.

Fig. 6 illustrates a square waveform of a signal injected on the power line from the generator shown in Fig. 5.

As will be understood from above description, the width of the square-wave signal is defined by a delay of turn-on of switching element 14 from turn-on of another switching element 16.

Therefore, the width is not varied dependent on variation of the load. Accordingly, a square-wave signal of a predetermined width can be stably and reliably provided to the equipment.

Resistor 15 is for protecting switching element 14 from a large current flowing therethrough. For improving the protection, an inductance coil 17 is also used in series with resistor 15, as shown in Fig. 7.

In the modification shown in Fig. 7, it is prevented by means of inductance coil 17 that a large current suddenly flow through switching element 14 at a time when switching element 14 is turned oii.

Referring to Fig. 8, another modification is shown, wherein a variable resistor 18 is additionally used in generator shown in Fig. 5.

Variable resistor 18 is connected between output terminals T1 and T2 to control the signal voltage generated so that variation of the amplitude of the signal generated due to connection of a different load may be compensated.

As shown in Fig. 9, a similar variable resistor 18 may be additionally used in the generator of Fig. 7.

In another aspect of this invention, a dampedwave signal generator is used as generator 3 in Fig. 3 or 4, for ringing-surge simulation of the equipment.

Referring to Fig. 10, a generator shown has a DC power supply 21. A capacitor 23 and an inductance coil 4 are seriesly connected to DC power supply 21 through a resistor 22. One end of the series circuit of capacitor 23 and inductance coil 24 is connected to an output terminal T, through switching element 25 such as a mechanical switch or an electrical switching element. The other end of the series circuit is connected to the other output terminal T2. Output terminals T, and T2 are connected to both sides T, and T2 of series resonance circuit 4~5 in Fig. 3 or 4, so that a damped-wave signal is injected onto the power line.

In the arrangement, capacitor 23 is charged by DC power supply 21 through resistor 22 and inductance coil 24. When switching element 25 is turned off, the charge of capacitor 23 is discharged to the equipment through the power line, switching element 25 and inductance coil 24. The discharge current vibrates at a frequency determined by the inductance of coil 24, capacitance of capacitor 23 and the impedance of the equipment, and its amplitude is attenuated at a rate determined by the impedance of the equipment. Accordingly, a damped-wave signal is fed to the equipment from the generator so that ringing-surge simulation of the equipment may be performed.

An example of a waveform of the dampedwave signal fed to the equipment from the generator of Fig. 10 is illustrated in Fig. 1 1.

In order to control the attenuating rate of the generated signal, a variable resistor 26 may be connected between output terminals T, and T2, as shown in Fig. 12. The variation of the attenuating rate due to the impedance difference of tested equipment can be compensated by adjusting variable resistor 26.

According to this invention, simulated-noise signal can be readily injected on the power line of the equipment under test, without no energy loss, in addition to no loss of AC power fed to the equipment.

Simulated lightening-strike signal can be reliably generated and injected on the power line so that lightening-strike simulation may be carried out with a high reliability.

Furthermore, simulated ringing-surge signal can be also generated so that a reliable simulation of the equipment against ringing surge may be performed.

Claims (filed 7/12/81) 1. A circuit for injecting simulated-noise signals onto the AC power line of the electric equipment under noise-simulating test, which comprises: series resonance means having a resonance frequency equal to a frequency of the AC power supply and connected in said AC power line to be in series with said electric equipment; capacitor means connected to said AC power line to be in parallel with said electric equipment and said series resonance means; and means for generating the simulating-noise signal, the output of which is connected across said series resonance means.

2. A circuit as claimed in Claim 1, which further comprises switching means connected in parallel with said series resonance means.

3. A circuit as claimed in Claim 1, wherein said series resonance means comprises inductance coil means and capacitor means connected in series with said coil means.

4. A circuit as claimed in Claim 1 , wherein said

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. connected to the other output terminal T2. The output terminals Tt and T2 are connected to both sides T and T2 of the series resonance circuit 4- Sin the power line 12, similar to in Fig. 3 or 4, so that the generated square wave may be injected on the power line. In the arrangement, capacitor 13 is charged by DC power supply through resistor 12. When switching element 16 is turned on, a discharge current of capacitor 13 is fed to the power line from output terminals T1 and T2 through switching element 16. Thereafter when switching element is turned on, the residual charge of capacitor 13 is discharged through resistor 1 5, so that feed of the discharge current to the power line is stopped. Accordingly, a square-wave signal is injected on the power line and lightening-strike simulation of the equipment can be performed. Fig. 6 illustrates a square waveform of a signal injected on the power line from the generator shown in Fig. 5. As will be understood from above description, the width of the square-wave signal is defined by a delay of turn-on of switching element 14 from turn-on of another switching element 16. Therefore, the width is not varied dependent on variation of the load. Accordingly, a square-wave signal of a predetermined width can be stably and reliably provided to the equipment. Resistor 15 is for protecting switching element 14 from a large current flowing therethrough. For improving the protection, an inductance coil 17 is also used in series with resistor 15, as shown in Fig. 7. In the modification shown in Fig. 7, it is prevented by means of inductance coil 17 that a large current suddenly flow through switching element 14 at a time when switching element 14 is turned oii. Referring to Fig. 8, another modification is shown, wherein a variable resistor 18 is additionally used in generator shown in Fig. 5. Variable resistor 18 is connected between output terminals T1 and T2 to control the signal voltage generated so that variation of the amplitude of the signal generated due to connection of a different load may be compensated. As shown in Fig. 9, a similar variable resistor 18 may be additionally used in the generator of Fig. 7. In another aspect of this invention, a dampedwave signal generator is used as generator 3 in Fig. 3 or 4, for ringing-surge simulation of the equipment. Referring to Fig. 10, a generator shown has a DC power supply 21. A capacitor 23 and an inductance coil 4 are seriesly connected to DC power supply 21 through a resistor 22. One end of the series circuit of capacitor 23 and inductance coil 24 is connected to an output terminal T, through switching element 25 such as a mechanical switch or an electrical switching element. The other end of the series circuit is connected to the other output terminal T2. Output terminals T, and T2 are connected to both sides T, and T2 of series resonance circuit 4~5 in Fig. 3 or 4, so that a damped-wave signal is injected onto the power line. In the arrangement, capacitor 23 is charged by DC power supply 21 through resistor 22 and inductance coil 24. When switching element 25 is turned off, the charge of capacitor 23 is discharged to the equipment through the power line, switching element 25 and inductance coil 24. The discharge current vibrates at a frequency determined by the inductance of coil 24, capacitance of capacitor 23 and the impedance of the equipment, and its amplitude is attenuated at a rate determined by the impedance of the equipment. Accordingly, a damped-wave signal is fed to the equipment from the generator so that ringing-surge simulation of the equipment may be performed. An example of a waveform of the dampedwave signal fed to the equipment from the generator of Fig. 10 is illustrated in Fig. 1 1. In order to control the attenuating rate of the generated signal, a variable resistor 26 may be connected between output terminals T, and T2, as shown in Fig. 12. The variation of the attenuating rate due to the impedance difference of tested equipment can be compensated by adjusting variable resistor 26. According to this invention, simulated-noise signal can be readily injected on the power line of the equipment under test, without no energy loss, in addition to no loss of AC power fed to the equipment. Simulated lightening-strike signal can be reliably generated and injected on the power line so that lightening-strike simulation may be carried out with a high reliability. Furthermore, simulated ringing-surge signal can be also generated so that a reliable simulation of the equipment against ringing surge may be performed. Claims (filed 7/12/81)

1. A circuit for injecting simulated-noise signals onto the AC power line of the electric equipment under noise-simulating test, which comprises: series resonance means having a resonance frequency equal to a frequency of the AC power supply and connected in said AC power line to be in series with said electric equipment; capacitor means connected to said AC power line to be in parallel with said electric equipment and said series resonance means; and means for generating the simulating-noise signal, the output of which is connected across said series resonance means.

4. A circuit as claimed in Claim 1 , wherein said simulated-noise signal generating means is square-wave generating means comprising DC power supply means, first resistor means and capacitor means connected to said DC power supply means in series with one another, a circuit branch including first switching means and second resistor means which is connected in series with said first switching means and connected across said capacitor means, second switching means one end of which is connected to one end of said series circuit branch, said first switching means turned on delayed after turning on said second switching means so that a square wave may present between the other end of said second switching means and the other end of said circuit branch.

5. A circuit as claimed in Claim 4, wherein said circuit branch further comprises inductance coil means in series with said first switching means and said second resistor means.

6. A circuit as claimed in Claim 4 or 5, which further comprises variable resistor means connected between the other end of said second switching means and the other end of said circuit branch.

7. A circuit as claimed in Claim 1 , wherein said simulated-noise signal generating means is damped-wave generating means comprising DC power supply means, resistor means one end of which is connected to said DC power supply, a circuit branch including capacitor means and inductance coil means which is connected in series with said capacitor means and connected across said DC power supply means and said resistor means, and switching means one end of which is connected to one end of said circuit branch, said switching means turned on to that a damped wave may present between the other end of said switching means and the other end of said circuit branch.

8. A circuit as claimed in Claim 7, which further comprises variable resistor means connected between the other end of said switching means and the other end of said circuit branch.

9. A circuit for injecting simulated-noise signals substantially as described herein with reference to Figs. 3, 4, 5 and 6, 7, 8, 9, 10 and 11 and Fig. 12 of the accompanying drawings.