US3742370A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Soft start a c motor control
Assignee: Cutler Hammer Inc
•
Filing: 1971-12-20
•
Granted: 1973-06-26
•
Expires: 1991-12-20
Abstract
Abstract A soft start control for a delta-connected motor or an ungrounded Y-connected (star-connected) motor or the like polyphase system. To reduce the accelerating torque of a polyphase motor and thereby obtain a soft start characteristic that reduces stress and strain on the driven parts until normal running speed is reached, a gated A.C. switching device such as a triac is used in the power lines of the polyphase A.C. source. A simple time delay firing circuit connected across each triac controls the latter so that current flow is interrupted in each of the phases for a predetermined period of time during each half-cycle in repetitive sequence, the net effect being to reduce the effective voltage applied to the motor. After a predetermined time of reduced voltage acceleration sufficient to bring the motor up to or near running speed, a timer controls the firing circuit to apply full line voltage to the motor.
Inventors
- 👤 J Hansen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 10:59
CPC Classifications
H; H02; H02P; H02P1/00; H02P1/16; H02P1/26; H02P1/28
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
257 words
A soft start polyphase control system comprising: a polyphase A.C. supply source; a polyphase A.C. load device having terminals; a plurality of gating type bidirectional switching means; means comprising power lines connecting said plurality of gating type bidirectional switching means between a plurality of the phases of said source and a plurality of said load terminals, respectively; a plurality of time-delay firing circuits connected for energization across the respective gating type bidirectional switching means, each said firing circuit being operable when the current in the associated gating type bidirectional switching means decreases to zero to delay refiring of the latter for a predetermined adjustable time interval thereby to interrupt for time intervals cyclically the current flow to the load devicE to reduce the power for soft starting; a plurality of no-delay firing circuits connected for by-passing the respective time-delay firing circuits, each being operable to fire the respective gating type bidirectional switching means into conduction at the beginning of each voltage halfcycle applied to the latter thereby to apply full power to the load device; and control means common to said time-delay and no-delay firing circuits comprising: means for initiating operation of the system including switching means responsive thereto for rendering said time-delay firing circuits operative thereby to apply reduced power to the load device for soft starting; timing means responsive to said initiation of operation of the system; and means responsive to said timing means after a predetermined time interval for rendering said no-delay firing circuits operative thereby to apply full power to the load device.
Claim 2
Dependent Claim
257 words
A soft start polyphase control system comprising: a polyphase A.C. supply source; a polyphase A.C. load device having terminals; a plurality of gating type bidirectional switching means; means comprising power lines connecting said plurality of gating type bidirectional switching means between a plurality of the phases of said source and a plurality of said load terminals, respectively; a plurality of time-delay firing circuits connected for energization across the respective gating type bidirectional switching means, each said firing circuit being operable when the current in the associated gating type bidirectional switching means decreases to zero to delay refiring of the latter for a predetermined adjustable time interval thereby to interrupt for time intervals cyclically the current flow to the load devicE to reduce the power for soft starting; a plurality of no-delay firing circuits connected for by-passing the respective time-delay firing circuits, each being operable to fire the respective gating type bidirectional switching means into conduction at the beginning of each voltage halfcycle applied to the latter thereby to apply full power to the load device; and control means common to said time-delay and no-delay firing circuits comprising: means for initiating operation of the system including switching means responsive thereto for rendering said time-delay firing circuits operative thereby to apply reduced power to the load device for soft starting; timing means responsive to said initiation of operation of the system; and means responsive to said timing means after a predetermined time interval for rendering said no-delay firing circuits operative thereby to apply full power to the load device.
Claim 3
Dependent Claim
29 words
The invention defined in claim 1, wherein said soft start polyphase control system also comprises: a plurality of dv/dt networks connected across the respective gating type bidirectional switching means.
Claim 4
Dependent Claim
60 words
The invention defined in claim 2, wherein said soft start polyphase control system further comprises: a plurality of resistors connected cross the respective time-delay firing circuits so as to be in parallel with the respective gating type bidirectional switching means when the associated time-delay firing circuit is rendered operative and to be disconnected by said switching means at other times.
Claim 5
Dependent Claim
43 words
The invention defined in claim 3, wherein said polyphase A.C. load device comprises: a delta connected A.C. motor having three phase terminals that are energized through three of said gating type bidirectional switching devices from three phases of said A.C. supply source, respectively.
Claim 6
Dependent Claim
56 words
The invention defined in claim 1, wherein said time-delay firing circuits comprise: means for adjusting said delayed symmetrical refiring of each gating type bidirectional switching device from zero delay (full on) to a phase angle short of any overlapping with a similar current interruption time interval in any of the other phases of the polyphase system.
Claim 7
Dependent Claim
47 words
The invention defined in claim 1, wherein each said time-delay firing circuit comprises: an RC time-delay circuit connected across the gating type bidirectional switching means; and a symmetrical trigger diode connected between said RC time delay circuit and the gate of said gating type bidirectional switching means.
Claim 8
Dependent Claim
63 words
The invention defined in claim 1, wherein said soft start polyphase control system also comprises: long conductors connecting said time-delay and no-delay firing circuits from remote locations to the respective gating type bidirectional switching means; and a noise voltage suppressor circuit connected to each gating type bidirectional switching means to suppress any noise voltages that may be picked up by said long conductors.
Claim 9
Dependent Claim
118 words
A soft start control system for controlling energization of a three-phase delta-connected or ungrounded Y-connected A.C. motor from a three-phase A.C. supply source comprising: three power lines each including a triac connecting the source to the motor; a time delay firing circuit energized across each said triac for firing the associated triac into conduction; and control means common to said triacs comprising: on-off means operable to start and stop the motor; means responsive to operation of said on-off means to start the motor for rendering said time-delay firing circuits effective to control application of reduced power to the motor; and means operable after a predetermined acceleration period for controlling said triacs to apply full line voltage to themotor.
Claim 10
Dependent Claim
118 words
A soft start control system for controlling energization of a three-phase delta-connected or ungrounded Y-connected A.C. motor from a three-phase A.C. supply source comprising: three power lines each including a triac connecting the source to the motor; a time delay firing circuit energized across each said triac for firing the associated triac into conduction; and control means common to said triacs comprising: on-off means operable to start and stop the motor; means responsive to operation of said on-off means to start the motor for rendering said time-delay firing circuits effective to control application of reduced power to the motor; and means operable after a predetermined acceleration period for controlling said triacs to apply full line voltage to themotor.
Claim 11
Dependent Claim
47 words
The invention defined in claim 8, wherein each said time-delay firing circuit comprises: an RC circuit connected for energization from across the anodes of the respective triac; and a Symmetrical trigger diode connected from the junction of said RC circuit to the gate of the associated triac.
Claim 12
Dependent Claim
39 words
The invention defined in claim 9, wherein said soft start control system also comprises: a dv/dt network comprising a resistor and a capacitor connected across each said triac; and a damping circuit connected across each RC time-delay firing circuit.
Claim 13
Dependent Claim
37 words
The invention defined in claim 10, wherein said damping circuit comprises: a resistor connected across each said time-delay firing circuit whereby this resistor becomes connected across the associated triac when said time-delay firing circuit is rendered effective.
Claim 14
Dependent Claim
69 words
The invention defined in claim 11, wherein said means operable after a predetermined acceleration period for controlling said triacs comprises: a timer for timing a predetermined time interval from the time of operation of said on-off means; and switching means responsive to said timer timing out at the end of said predetermined time interval for shunting each time-delay firing circuit to cause full line voltage firing of said triacs.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-06-25 | 1976-12-25 | 1977-06-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-06-25 | 1980-12-25 | 1981-06-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-06-25 | 1984-12-25 | 1985-06-26 | $7700.00 | Window Closed / Lapsed |