EP0081275A2
Expired / Lapsed
EP
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Improved power inverter
Assignee: Tocco Inc
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Filing: 1982-06-10
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Granted: —
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Expires: 2002-06-10
Abstract
Abstract An improvement is provided in a power inverter for converting a D.C. current into alternating current having a frequency controlled by the rate at which a series of gating signals are created, which inverter includes first and second branches controlled by separate switching means to create the alternating current through the load. The improvement is the provision of a starting inverter having a D.C. input and an A.C. output with a frequency controlled by a series of repeating gating commands, means for selectively applying the A.C. output of the starting inverter across the load until a preselected load condition exist and an arrangement for controlling the frequency of the gating command in the starting inverter to produce a generally unity power factor across the load during the starting cycle. The improved inverter includes a circuit responsive to the voltage wave across the load for controlling the firing position of the gating signals. Also, a method of operating a power inverter including provision of a separate starting inverter having an alternating current output with a frequency controlled by repetitive gating commands, connecting the output of the starting inverter across the load, energizing the starting inverter, adjusting the frequency of the gating command to produce a substantially unity power factor across the load, maintaining the power factor for a starting cycle and then energizing the power inverter for normal operation.
Inventors
- 👤 Shashi Bhushan Dewan
- 👤 Graham Ross Adams
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-02 22:56
CPC Classifications
H; H02; H02M; H02M7/00; H02M7/42; H02M7/44; H02M7/48; H02M7/505; H02M7/515; H02M7/525; H02M7/527; H02M7/529
Claims Analysis
Total Claims: 43
Claim 1
Independent Claim
161 words
A power inverter for converting a D.C. current into alternating current having a frequency controlled by the rate at which a series of gating signals are created, said inverter including control means for selectively energizing said power inverter, a first branch to be connected across a load, a second branch to be connected across said load, first switching means for applying a voltage of a first polarity across said load by said first branch, second switching means for applying a voltage of a second polarity across said load by said second branch and means for alternately operating said first and second switching means by said series of gating signals, characterised by: a starting inverter having a D.C. input and an A.C. output with a frequency .controlled by a series of repeating gating commands, means for selectively applying said A.C. output across said load until a preselected condition exists and means responsive to the existence of said condition'for energizing said power inverter.
Claim 2
Dependent Claim
161 words
A power inverter for converting a D.C. current into alternating current having a frequency controlled by the rate at which a series of gating signals are created, said inverter including control means for selectively energizing said power inverter, a first branch to be connected across a load, a second branch to be connected across said load, first switching means for applying a voltage of a first polarity across said load by said first branch, second switching means for applying a voltage of a second polarity across said load by said second branch and means for alternately operating said first and second switching means by said series of gating signals, characterised by: a starting inverter having a D.C. input and an A.C. output with a frequency .controlled by a series of repeating gating commands, means for selectively applying said A.C. output across said load until a preselected condition exists and means responsive to the existence of said condition'for energizing said power inverter.
Claim 3
Dependent Claim
17 words
A power inverter as defined in claim 1, wherein said load condition is a preselected load voltage.
Claim 4
Dependent Claim
15 words
A power inverter as defined in claim 1, wherein said condition is average load voltage.
Claim 5
Dependent Claim
24 words
A power inverter as defined in claim 1, wherein said load condition is a preselected time after applying said starting inverter across said load.
Claim 6
Dependent Claim
17 words
A power inverter as defined in any one of the preceding claims, including means for disconnecting said
Claim 7
Dependent Claim
18 words
A.C. output or said starting inverter from said load in timed relationship with energizing said power inverter. -
Claim 8
Dependent Claim
18 words
A.C. output or said starting inverter from said load in timed relationship with energizing said power inverter. -
Claim 9
Dependent Claim
47 words
A power inverter as defined in any one of the preceding claims including means for detecting the voltage across said load, means for detecting the current flowing through said load and means for adjusting said repetitive gating commands until said voltage and current are generally in phase.
Claim 10
Dependent Claim
58 words
A power inverter as defined in claim 6, wherein said adjusting means includes means for creating a control signal generally proportional to the phase displacement between said load current and said load voltage and means for changing said frequency of said repetitive gating commands in response to said phase displacement in a direction to decrease said phase displacement.
Claim 11
Dependent Claim
64 words
A power inverter as defined in claim 7, wherein said means for creating a control signal includes means for integrating said alternating load voltage and means for multiplying said integrated load voltage with said load current to produce D.C. average voltage level; means for comparing said voltage level with a reference level; and, means for creating said control signal in response to said comparison.
Claim 12
Dependent Claim
50 words
. A power inverter as defined in claim 6 or 7 wherein said adjusting means includes means for integrating said detected load voltage, means for multiplying said integrated load voltage with said detected load current and means responsive to said product for adjusting said frequency of said repetitive gating commands.
Claim 13
Dependent Claim
39 words
A power inverter as defined in any one of the preceding claims, wherein said starting inverter includes two separate circuits for alternating current through said load and a single gate command responsive switching device in each of said circuits.
Claim 14
Dependent Claim
26 words
A power inverter as defined in any one of the preceding claims wherein said energizing means includes means for increasing the power to said power inverter.
Claim 15
Dependent Claim
25 words
A power inverter as defined in any one of the preceding claims wherein said energizing means includes means for creating said series of gating signals.
Claim 16
Dependent Claim
125 words
1 3 . A method of operating a power inductor of the type used in induction heating of a load and having a frequency controlled by the rate at which a series of gating signals are created, said method comprising the steps of: (a) providing a separate starting inverter having an alternating current output with a frequency controlled by repetitive gating commands; (b) connecting said output of said separate starting inverter across said load; (c) energizing said connected starting inverter; (d) adjusting said frequency of said repetitive gating commands to produce substantially a unity power factor across said load; (e) maintaining said unity power factor from said starting inverter; (f) energizing said power inverter after said starting inverter has been adjusted to unity power factor.
Claim 17
Dependent Claim
125 words
1 3 . A method of operating a power inductor of the type used in induction heating of a load and having a frequency controlled by the rate at which a series of gating signals are created, said method comprising the steps of: (a) providing a separate starting inverter having an alternating current output with a frequency controlled by repetitive gating commands; (b) connecting said output of said separate starting inverter across said load; (c) energizing said connected starting inverter; (d) adjusting said frequency of said repetitive gating commands to produce substantially a unity power factor across said load; (e) maintaining said unity power factor from said starting inverter; (f) energizing said power inverter after said starting inverter has been adjusted to unity power factor.
Claim 18
Dependent Claim
17 words
A method as defined in claim 13 wherein said power inverter is energized after a preselected time.
Claim 19
Dependent Claim
24 words
15 . A method as defined in claim 13 wherein said power inverter is energized after the voltage across said load reaches a preselected.value.
Claim 20
Dependent Claim
81 words
1 6. A method as defined in claim 13 wherein said adjusting step includes: (g) detecting the load voltage to obtain a voltage wave; (h) detecting the load current to obtain a current wave; (i) shifting the time displacement of one of said waves by substantially 90°; (j) multiplying said shifted wave with the non-shifted wave; (k) comparing the product of said multiplication with a reference to produce a control signal; and, (1) adjusting said frequency by said control signal.. -
Claim 21
Dependent Claim
18 words
. 17 . A method as defined in claim 16 wherein said shifting is in a positive direction.-
Claim 22
Dependent Claim
104 words
A circuit for controlling the frequency of gating signals for the switching devices of a D.C. to A.C. inverter having an output to be connected across a load, said circuit comprising: means for detecting the load voltage ,to obtain a voltage wave; means for detecting the load current to obtain a current wave; means for shifting one of said waves by substantially 90°; means for multiplying said one wave and the other of said waves; means for comparing said product with a reference to produce a control. signal; and means for adjusting the frequency of said gating signals in accordance with said control signal..
Claim 23
Dependent Claim
104 words
A circuit for controlling the frequency of gating signals for the switching devices of a D.C. to A.C. inverter having an output to be connected across a load, said circuit comprising: means for detecting the load voltage ,to obtain a voltage wave; means for detecting the load current to obtain a current wave; means for shifting one of said waves by substantially 90°; means for multiplying said one wave and the other of said waves; means for comparing said product with a reference to produce a control. signal; and means for adjusting the frequency of said gating signals in accordance with said control signal..
Claim 24
Dependent Claim
16 words
19 . A circuit as defined in claim 18 wherein said shifting means is an integrator.
Claim 25
Dependent Claim
14 words
A circuit as defined in claim 18 wherein said detected voltage wave is shifted.
Claim 26
Dependent Claim
65 words
21 A method of controlling the frequency of gating signals for the switching devices of a D.C. to A.C. inverter having an output to be connected to a load, said method comprising the steps of: (a) shifting a detected load voltage wave by 90°; (b) multiplying the shifted wave by the load current wave; (c) using the product of said multiplication to control said frequency.
Claim 27
Dependent Claim
65 words
21 A method of controlling the frequency of gating signals for the switching devices of a D.C. to A.C. inverter having an output to be connected to a load, said method comprising the steps of: (a) shifting a detected load voltage wave by 90°; (b) multiplying the shifted wave by the load current wave; (c) using the product of said multiplication to control said frequency.
Claim 28
Dependent Claim
89 words
2 2 . A circuit .for creating repetitive gating signals for the switching devices of a D.C. to A.C. power inverter, which signals are created in timed relationship with respect to the voltage wave having alternate positive and negative segments and directed across a load connected to said inverter, said switching devices having a known minimum commutating time, said circuit comprising: means for establishing a reference time when said voltage transfers between said alternate segments and means for creating a gating signal a preselected time after said reference time.
Claim 29
Dependent Claim
89 words
2 2 . A circuit .for creating repetitive gating signals for the switching devices of a D.C. to A.C. power inverter, which signals are created in timed relationship with respect to the voltage wave having alternate positive and negative segments and directed across a load connected to said inverter, said switching devices having a known minimum commutating time, said circuit comprising: means for establishing a reference time when said voltage transfers between said alternate segments and means for creating a gating signal a preselected time after said reference time.
Claim 30
Dependent Claim
34 words
A circuit as defined in claim 22 wherein said preselected time is substantially the measured time between successive instances of voltage transfer-minus a known time exceeding the known minimum commutating time of.said switching devices.
Claim 31
Dependent Claim
58 words
A circuit as defined in claim 23 including means for sensing the time-of a transfer between adjacent wave segments, means for creating a known value representing said preselected time, means for incrementing a control .signal from said sensed time toward said known value and means for creating a gating signal when said control signal reaches said known value.
Claim 32
Dependent Claim
45 words
A circuit as defined in claim 24 wherein said known value is a voltage level and said control signal is a voltage signal and said incrementing means includes means for progressively increasing said control signal until it equals the voltage level of said known value.
Claim 33
Dependent Claim
20 words
A circuit as defined in claim 25 wherein said known value is controlled by prior segments of said voltage wave.
Claim 34
Dependent Claim
98 words
A circuit as defined in claim 22 including means for providing clocking pulses with a known frequency; means for sensing a wave transfer initiating a selected segment; means for counting said pulses during said selected segment to produce a control count for a successive wave segment; means for substrating from said control count a selected number to produce a gating number for said successive segment representing a reference time; means for counting said pulses during said successive segment until reaching said gating number; and creating a gating pulse when said gating number is reached during said successive segment.
Claim 35
Dependent Claim
22 words
A circuit as defined in claim 27 including means for holding said gating pulse for a preselected number of said clocking pulses.
Claim 36
Dependent Claim
208 words
An inverter for converting a D.C. current into alternating current having a frequency controlled by the rate at which a series of gating signals are created, said inverter including a first branch to be connected across a load, a second branch to be connected across said load, first switching means for applying a voltage of a first polarity across said load by said first branch, second switching means for applying a voltage of a second polarity across said load by said second branch and means'for alternately operating said switching means by said series of gating signals whereby a voltage wave having alternating positive and negative segments is applied across said load, - further comprising: means for providing clocking pulses with a known frequency; means for sensing a wave transfer between adjacent segments at the start of a selected segment; means for counting said pulses during said selected segment to produce a control count for a successive wave segment; means for substrating from said control count a selected number to produce a gating number for said successive segment; means for counting said pulses during said successive segment until reaching said gating number; and means for creating a gating pulse when said gating number is reached during said successive segment.
Claim 37
Dependent Claim
208 words
An inverter for converting a D.C. current into alternating current having a frequency controlled by the rate at which a series of gating signals are created, said inverter including a first branch to be connected across a load, a second branch to be connected across said load, first switching means for applying a voltage of a first polarity across said load by said first branch, second switching means for applying a voltage of a second polarity across said load by said second branch and means'for alternately operating said switching means by said series of gating signals whereby a voltage wave having alternating positive and negative segments is applied across said load, - further comprising: means for providing clocking pulses with a known frequency; means for sensing a wave transfer between adjacent segments at the start of a selected segment; means for counting said pulses during said selected segment to produce a control count for a successive wave segment; means for substrating from said control count a selected number to produce a gating number for said successive segment; means for counting said pulses during said successive segment until reaching said gating number; and means for creating a gating pulse when said gating number is reached during said successive segment.
Claim 38
Dependent Claim
24 words
30 . An inverter as defined in claim 29 including means for holding said gating pulse for a preselected number of said clocking pulses.
Claim 39
Dependent Claim
171 words
31 . A - power inverter for converting a D.C. current into alternating current having a frequency controlled by the rate at which a series of gating signals are created, said inverter including control means for energizing said power inverter, a first branch to be connected across a load, a second branch to be connected across said load, first switching means for applying a voltage of a first polarity across said load by said first branch, second switching means for applying a voltage of a second polarity across said load by said second branch and means for alternately operating said first and second switching means by said series of gating signals, further comprising: a starting inverter having a D.C. input and an A.C. output with a frequency controlled by a series of repeating gating commands, means for selectively applying said A.C. output across said load until a preselected load condition exists and means for controlling the frequency of said gating commands to produce a generally unity power factor across said load.
Claim 40
Dependent Claim
171 words
31 . A - power inverter for converting a D.C. current into alternating current having a frequency controlled by the rate at which a series of gating signals are created, said inverter including control means for energizing said power inverter, a first branch to be connected across a load, a second branch to be connected across said load, first switching means for applying a voltage of a first polarity across said load by said first branch, second switching means for applying a voltage of a second polarity across said load by said second branch and means for alternately operating said first and second switching means by said series of gating signals, further comprising: a starting inverter having a D.C. input and an A.C. output with a frequency controlled by a series of repeating gating commands, means for selectively applying said A.C. output across said load until a preselected load condition exists and means for controlling the frequency of said gating commands to produce a generally unity power factor across said load.
Claim 41
Dependent Claim
30 words
A power inverter as defined in claim 31 including means for disconnecting said A.C. output of said starting inverter from said load in timed relationship with energizing said power inverter.
Claim 42
Dependent Claim
20 words
or 32 33 . A power inverter as defined in claim 31/wherein said load condition is a preselected load voltage.
Claim 43
Dependent Claim
46 words
32 or 33 34 . A power inverteras defined in claim 31,including means for detecting the voltage across said load, means for detecting the current flowing through said load and means for adjusting said repetitive gating commands until said voltage and current are generally in phase.
References Cited (Backward Citations)
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