US4311948A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Dynamic braking of A.C. motors
Assignee: National Research Development Corp UK
•
Filing: 1979-04-02
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Granted: 1982-01-19
•
Expires: 1999-04-02
Abstract
Abstract A three-phase electric motor is partially braked as a result of self-excitation when the power supply is disconnected and a capacitor is connected across one of the windings. The motor is then rapidly brought to a standstill by applying a short-circuit (or connecting a relatively low impedance) across one or both of the other windings, and essential condition being that the short-circuit is initiated within a predetermined range of values of phase angle in a waveform of the self-excitation. Preferred ranges of phase angle are established for selected configurations of mechanical and electronic short-circuiting switches.
Inventors
- 👤 Joseph E. Brown
- 👤 Charles R. Gamble
- 👤 Frank Norman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 17:56
CPC Classifications
H; H02; H02P; H02P3/00; H02P3/06; H02P3/18; H02P3/22
Claims Analysis
Total Claims: 60
Claim 1
Independent Claim
158 words
Control apparatus for the dynamic braking of an induction motor having primary windings of polyphase form and a plurality of pairs of terminals associated therewith, comprising: a capacitor; switching means operative subsequent to the disconnection of said motor from a power supply for connecting said capacitor across a first pair of terminals of said primary windings to establish self-excitation in said primary windings; and control means operative after a predetermined delay from the connection of said capacitor during which initial braking occurs, for obtaining a respective low impedance path across at least a second pair of terminals of said primary windings other than said terminals across which said capacitor is connected following the occurrence of a selected phase reference condition in a self-excitation wave form of said motor, conduction in the low impedance path across said second pair of terminals being initiated within a predetermined portion of a cycle of said self-excitation wave form to obtain further braking.
Claim 2
Dependent Claim
158 words
Control apparatus for the dynamic braking of an induction motor having primary windings of polyphase form and a plurality of pairs of terminals associated therewith, comprising: a capacitor; switching means operative subsequent to the disconnection of said motor from a power supply for connecting said capacitor across a first pair of terminals of said primary windings to establish self-excitation in said primary windings; and control means operative after a predetermined delay from the connection of said capacitor during which initial braking occurs, for obtaining a respective low impedance path across at least a second pair of terminals of said primary windings other than said terminals across which said capacitor is connected following the occurrence of a selected phase reference condition in a self-excitation wave form of said motor, conduction in the low impedance path across said second pair of terminals being initiated within a predetermined portion of a cycle of said self-excitation wave form to obtain further braking.
Claim 3
Dependent Claim
62 words
An apparatus according to claim 1 further comprising: delay means responsive to the operation of said switching means to produce a first enabling signal after said predetermined delay; and phase selection means responsive to the occurrence of said selected phase reference condition to produce a second enabling signal, said control means being operative in response to said first and second enabling signals.
Claim 4
Dependent Claim
23 words
An apparatus according to claim 2 in which said phase-selection means comprises a phase-shift network having a voltage input from a primary winding.
Claim 5
Dependent Claim
22 words
An apparatus according to claim 2 in which said phase-selection means includes means responsive to a parameter of the capacitor current waveform.
Claim 6
Dependent Claim
30 words
An apparatus according to claim 2 in which said phase selection means includes means for causing a predetermined delay in transmission of said second enabling signal to said control means.
Claim 7
Dependent Claim
39 words
An apparatus according to claim 1 in which said control means includes: normally non-conducting switch means operative to produce each respective low-impedance path; and trigger means operative to transmit a trigger signal to enable said normally non-conducting switch means.
Claim 8
Dependent Claim
32 words
An apparatus according to claim 6 in which said trigger means includes: means for producing a repetitive trigger signal; and means for transmitting said trigger signal to said normally non-conducting switch means.
Claim 9
Dependent Claim
18 words
An apparatus according to claim 6 in which said normally non-conducting switch means is bi-directionally conductive when conductive.
Claim 10
Dependent Claim
20 words
An apparatus according to claim 8 in which a low-impedance path is obtained across only said second pair of terminals.
Claim 11
Dependent Claim
62 words
An apparatus according to claim 9 in which said predetermined portion of a cycle comprises, within each time quadrant of said self-excitation waveform in which there occurs a zero-crossing in a voltage waveform of the winding associated with the low-impedance path obtained across said second pair of terminals, a sector which extends through approximately thirty degrees on each side of said zero-crossing.
Claim 12
Dependent Claim
35 words
An apparatus according to claim 8 in which respective low impedance paths are obtained across all respective pairs of terminals, other than said first pair of terminals, associated with respective windings of said primary windings.
Claim 13
Dependent Claim
15 words
An apparatus according to claim 11 in which said respective low-impedance paths are obtained simultaneously.
Claim 14
Dependent Claim
26 words
An apparatus according to claim 12 in which said predetermined portion of a cycle is substantially a zero crossing in a voltage waveform of said capacitor.
Claim 15
Dependent Claim
18 words
An apparatus according to claim 6 in which said normally non-conducting switch means is uni-directionally conductive when conductive.
Claim 16
Dependent Claim
33 words
An apparatus according to claim 14 in which said normally non-conducting switch means comprises a first uni-directional switch means operative such that a low-impedance path is obtained across said second pair of terminals.
Claim 17
Dependent Claim
72 words
An apparatus according to claim 15 in which said predetermined portion of a cycle lies within each time quadrant of said self-excitation waveform in which a voltage waveform of the winding associated with the low impedance path obtained across said second pair of terminals changes sign to that favorable to conduction through said switch means, said predetermined portion of a cycle comprising a sector of approximately 15° following said change of sign.
Claim 18
Dependent Claim
63 words
An apparatus according to claim 16 in which said trigger means is operative to commence transmission of said trigger signal within a half-cycle of the voltage waveform of the winding associated with the low impedance path obtained across said second pair of terminals preceding said change of sign such that `lie-in-wait` triggering occurs to obtain conduction substantially immediately following said change of sign.
Claim 19
Dependent Claim
48 words
An apparatus according to claim 15 in which said normally non-conducting switch means further comprises a second uni-directional switch means operative in consequence of conduction in the low impedance path obtained across said second pair of terminals to obtain a low-impedance path across a third pair of terminals.
Claim 20
Dependent Claim
74 words
An apparatus according to claim 18 in which said first uni-directional switch means is operative prior to said second uni-directional switch means, said predetermined portion of a cycle occurring in an earlier time quadrant than another predetermined portion of a cycle of said self-excitation waveform associated with an initiation of a low-impedance path across said third pair of terminals absent the influence of the low impedance path obtained across said second pair of terminals.
Claim 21
Dependent Claim
27 words
An apparatus according to claim 1 in which said control means is energised from an auxiliary power supply derived from one of said primary windings during self-excitation.
Claim 22
Independent Claim
113 words
An apparatus for dynamically braking an induction motor having primary windings of polyphase form and a plurality of terminals associated therewith, comprising: a capacitor; switch means for controlling the connection of said capacitor across one pair of self-excitation terminals to obtain initial braking of said motor; control means for providing a low impedance path across at least a different pair of braking control terminals; and means responsive to a self-excitation wave form of said motor for enabling said control means at a predetermined phase angle of said self-excitation wave form, conduction thereby being able to occur through the low impedance path provided by said control means to obtain further braking of said motor.
Claim 23
Independent Claim
113 words
An apparatus for dynamically braking an induction motor having primary windings of polyphase form and a plurality of terminals associated therewith, comprising: a capacitor; switch means for controlling the connection of said capacitor across one pair of self-excitation terminals to obtain initial braking of said motor; control means for providing a low impedance path across at least a different pair of braking control terminals; and means responsive to a self-excitation wave form of said motor for enabling said control means at a predetermined phase angle of said self-excitation wave form, conduction thereby being able to occur through the low impedance path provided by said control means to obtain further braking of said motor.
Claim 24
Dependent Claim
47 words
An apparatus as in claim 21 further comprising means responsive to removal of power from said motor for enabling said control means after a predetermined delay period, said control means being operative after enabled by both said phase angle enabling means and said delay period enabling means.
Claim 25
Dependent Claim
58 words
An apparatus as in claim 21 or 22, wherein said control means comprises a normally nonconductive unidirectional switching device connected across a first pair of braking control terminals, conduction therethrough ensuing, once said control means is enabled, when the level and polarity of voltage present at said first pair of braking control terminals satisfies a predetermined trigger condition.
Claim 26
Dependent Claim
61 words
An apparatus as in claim 23, wherein said self-excitation waveform is a voltage waveform of a primary winding associated with said first pair of braking control terminals, and wherein said predetermined phase angle is within a range of approximately fifteen degrees following a change in sign of said self-excitation waveform to a polarity favorable to conduction in said unidirectional switching device.
Claim 27
Dependent Claim
80 words
An apparatus as in claim 23, wherein said self-excitation waveform is a current waveform of said capacitor, and wherein said predetermined phase angle is within a time quadrant of said self-excitation waveform in which a voltage waveform of a primary winding associated with said first pair of braking control terminals changes sign to a polarity favorable to conduction in said uni-directional switching device, said predetermined phase angle being within a range of approximately fifteen degrees following said change in sign.
Claim 28
Dependent Claim
57 words
An apparatus as in claim 23, wherein said control means comprises another normally nonconductive unidirectional switching device connected across a second pair of braking control terminals, conduction therethrough ensuing subsequent to conduction through said first-mentioned unidirectional switching device when the level of voltage present at said second pair of braking control terminals satisfies a predetermined trigger condition.
Claim 29
Dependent Claim
31 words
An apparatus as in claim 23, wherein said control means further comprises: means for generating a periodic trigger signal; and means for transmitting said trigger signal to said unidirectional switching device.
Claim 30
Dependent Claim
30 words
An apparatus as in claim 21 or 22, wherein said control means comprises a normally nonconductive bidirectional switch, conduction therethrough occurring substantially simultaneously with the enabling of said control means.
Claim 31
Dependent Claim
52 words
An apparatus as in claim 28, wherein said self-excitation waveform is a voltage waveform of a primary winding associated with said first pair of braking control terminals, and wherein said predetermined phase angle is within a range of approximately thirty degrees on either side of the zero crossing of said self-excitation waveform.
Claim 32
Dependent Claim
16 words
An apparatus as in claim 29, wherein said predetermined phase angle corresponds to said zero crossing.
Claim 33
Dependent Claim
73 words
An apparatus as in claim 28, wherein said self-excitation waveform is a current waveform of said capacitor, and wherein said predetermined phase angle is within a time quadrant of said self-excitation waveform in which a voltage waveform of a primary winding associated with said first pair of braking control terminals has a zero crossing, said predetermined phase angle being within a range of approximately thirty degrees on each side of said zero crossing.
Claim 34
Dependent Claim
16 words
An apparatus as in claim 31, wherein said predetermined phase angle corresponds to said zero crossing.
Claim 35
Dependent Claim
38 words
An apparatus as in claim 28, wherein said control means comprises another normally nonconductive bidirectional switch connected across a second pair of braking control terminals, conduction therethrough being obtained substantially simultaneously with conduction through said first-mentioned bidirectional switch.
Claim 36
Dependent Claim
37 words
An apparatus as in claim 21, wherein said control means enabling means comprises a phase shift network, said self-excitation waveform being a voltage waveform of a primary winding associated with a first pair of braking control terminals.
Claim 37
Dependent Claim
37 words
An apparatus as in claim 24, wherein said control means enabling means comprises a phase shift network, said self-excitation waveform being a voltage waveform of a primary winding associated with said first pair of braking control terminals.
Claim 38
Dependent Claim
37 words
An apparatus as in claim 29, wherein said control means enabling means comprises a phase shift network, said self-excitation waveform being a voltage waveform of a primary winding associated with said first pair of braking control terminals.
Claim 39
Dependent Claim
53 words
An apparatus as in claim 21, wherein said control means enabling means comprises: a current transformer for sensing said self-excitation waveform, said self-excitation waveform being a current waveform of said capacitor; and a phase selector responsive to the output of said current sensor for enabling said control means at said predetermined phase angle.
Claim 40
Dependent Claim
53 words
An apparatus as in claim 25, wherein said control means enabling means comprises: a current transformer for sensing a self-excitation waveform, said self-excitation waveform being a current waveform of said capacitor; and a phase selector responsive to the output of said current sensor for enabling said control means at said predetermined phase angle.
Claim 41
Dependent Claim
53 words
An apparatus as in claim 31, wherein said control means enabling means comprises: a current transformer for sensing said self-excitation waveform, said self-excitation waveform being a current waveform of said capacitor; and a phase selector responsive to the output of said current sensor for enabling said control means at said predetermined phase angle.
Claim 42
Independent Claim
138 words
A method for dynamically braking an induction motor having primary windings of polyphase form and a plurality of terminals associated therewith, comprising the steps of: removing power from said motor; establishing self-excitation in said primary windings by connecting a capacitor across one of the primary windings, subsequent to said power removal step, for obtaining initial braking of said motor; and enabling a low impedance path across a preselected first primary winding of said primary windings different than the one of the primary windings having a capacitor connected thereacross, subsequent to a predetermined delay period during which initial braking of said motor occurs, at a predetermined phase angle of a self-excitation wave form of said motor, conduction thereby being able to occur through the low impedance path across said first primary winding to obtain further braking of said motor.
Claim 43
Independent Claim
138 words
A method for dynamically braking an induction motor having primary windings of polyphase form and a plurality of terminals associated therewith, comprising the steps of: removing power from said motor; establishing self-excitation in said primary windings by connecting a capacitor across one of the primary windings, subsequent to said power removal step, for obtaining initial braking of said motor; and enabling a low impedance path across a preselected first primary winding of said primary windings different than the one of the primary windings having a capacitor connected thereacross, subsequent to a predetermined delay period during which initial braking of said motor occurs, at a predetermined phase angle of a self-excitation wave form of said motor, conduction thereby being able to occur through the low impedance path across said first primary winding to obtain further braking of said motor.
Claim 44
Dependent Claim
34 words
A method as in claim 40, wherein conduction through the low impedance path across said first primary winding occurs when the level of voltage of said first primary winding satisfies a predetermined trigger condition.
Claim 45
Dependent Claim
82 words
A method as in claim 41 further comprising the step of enabling a low impedance path across a preselected second primary winding of said primary windings concurrent with said step of enabling a low impedance path across a preselected first primary winding, conduction occurring through the low impedance path across said second primary winding subsequently to conduction through the low impedance path across said first primary winding when the level of voltage of said second primary winding satisfies a predetermined trigger condition.
Claim 46
Dependent Claim
88 words
A method as in claim 41 further comprising the step of enabling a low impedance path across a preselected second primary winding of said primary windings, subsequent to said predetermined delay period, at another predetermined phase angle of said self-excitation waveform greater than said first-mentioned predetermined phase angle, conduction occurring through the low impedance path across said second primary winding subsequently to conduction through the low impedance path across said first primary winding when the level of voltage of said second primary winding satisfies a predetermined trigger condition.
Claim 47
Dependent Claim
100 words
A method as in claim 41, wherein said self-excitation waveform is the voltage waveform of said first primary winding, further comprising the step of enabling a low impedance path across a preselected second primary winding of said primary windings, subsequent to said predetermined delay period, at a predetermined phase angle of a voltage waveform of said second primary winding, conduction thereby occurring through the low impedance path across said second primary winding subsequently to conduction through the low impedance path across said first primary winding when the level of voltage of said second primary winding satisfies a predetermined trigger condition.
Claim 48
Dependent Claim
35 words
A method as in claim 40, wherein conduction through the low impedance path across said first primary winding occurs concurrently with said step of enabling a low impedance path across a preselected first primary winding.
Claim 49
Dependent Claim
67 words
A method as in claim 45 further comprising the step of enabling a low impedance path across a preselected second primary winding of said primary windings concurrent with said step of enabling a low impedance path across a preselected first primary winding, conduction occurring through the low impedance path across said second primary winding concurrently with conduction through the low impedance path across said first primary winding.
Claim 50
Dependent Claim
88 words
A method as in claim 45 further comprising the step of enabling a low impedance path across a preselected second primary winding of said primary windings, subsequent to said predetermined delay period, at another predetermined phase angle of said self-excitation waveform greater than said first-mentioned predetermined phase angle, conduction occurring through the low impedance path across said second primary winding subsequently to conduction through the low impedance path across said first primary winding and concurrently with the enabling of the low impedance path across said second primary winding.
Claim 51
Dependent Claim
99 words
A method as in claim 45, wherein said self-excitation waveform is the voltage waveform of said first primary winding, further comprising the step of enabling a low impedance path across a preselected second primary winding of said primary windings, subsequent to said predetermined delay period, at a predetermined phase angle of a voltage waveform of said second primary winding, conduction occurring through the low impedance path across said second primary winding subsequently to conduction through the low impedance path across said first primary winding and concurrently with the enabling of a low impedance path across said second primary winding.
Claim 52
Dependent Claim
25 words
A method as in claim 40, 41, 42, 43, 45, 46 or 47, wherein said self-excitation waveform of said motor is a self-excitation current waveform.
Claim 53
Dependent Claim
29 words
A method as in claim 40, 41, 42, 43, 45, 46 or 47, wherein said self-excitation waveform of said motor is the voltage waveform of said first primary winding.
Claim 54
Dependent Claim
18 words
A method as in claim 40, wherein said primary winding is delta-connected for connection to a three-phase supply.
Claim 55
Dependent Claim
18 words
A method as in claim 40, wherein said primary windings are star-connected for connection to a three-phase supply.
Claim 56
Independent Claim
142 words
A method for dynamically braking an induction motor having primary windings of polyphase form and a plurality of terminals associated therewith, comprising the steps of: removing power from said motor; establishing self-excitation in said primary windings by connecting a capacitor across a series arrangement of a first predetermined one and a second predetermined one of said primary windings, said primary windings being connected in quadrature for connection to a single-phase supply, for obtaining initial braking of said motor; and enabling a low impedance path across a preselected one of said primary windings, subsequent to a predetermined delay period during which initial braking of said motor occurs, at a predetermined phase angle of a self-excitation wave form of said motor conduction thereby being able to occur through the low impedance path across said first primary winding to obtain further braking of said motor.
Claim 57
Independent Claim
142 words
A method for dynamically braking an induction motor having primary windings of polyphase form and a plurality of terminals associated therewith, comprising the steps of: removing power from said motor; establishing self-excitation in said primary windings by connecting a capacitor across a series arrangement of a first predetermined one and a second predetermined one of said primary windings, said primary windings being connected in quadrature for connection to a single-phase supply, for obtaining initial braking of said motor; and enabling a low impedance path across a preselected one of said primary windings, subsequent to a predetermined delay period during which initial braking of said motor occurs, at a predetermined phase angle of a self-excitation wave form of said motor conduction thereby being able to occur through the low impedance path across said first primary winding to obtain further braking of said motor.
Claim 58
Dependent Claim
44 words
A method as in claim 42, 43, 46 or 47, wherein said step of establishing self-excitation comprises the step of connecting a capacitor across a preselected third primary winding of said primary windings, said primary windings being delta-connected for connection to a three-phase supply.
Claim 59
Dependent Claim
44 words
A method as in claim 42, 43, 46 or 47 wherein said step of establishing self-excitation comprises the step of connecting a capacitor across a preselected third primary winding of said primary windings, said primary windings being star-connected for connection to a three-phase supply.
Claim 60
Dependent Claim
48 words
A method as in claim 42, 43, 46 or 47 wherein said step of establishing self-excitation comprises the step of connecting a capacitor across the series arrangement of said first and said second primary windings, said primary windings being connected in quadrature for connection to a single-phase supply.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1985-01-18 | 1985-07-20 | 1986-01-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-01-18 | 1989-07-20 | 1990-01-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-01-18 | 1993-07-20 | 1994-01-19 | $7700.00 | Window Closed / Lapsed |