US3896369A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Circuit for soft-starting electric load comprising temperature sensitive diac
Assignee: Mitsubishi Electric Corp
•
Filing: 1974-08-27
•
Granted: 1975-07-22
•
Expires: 1994-08-27
Abstract
Abstract A circuit for triggering a bidirectional thyristor having a capacitor charged from an ac source includes a semiconductor thermally sensitive switch having a break-over voltage dependent upon a temperature and applied with a voltage across the capacitor. Upon the closure of an ON-OFF switch, the capacitor voltage reaches the break-over voltage to break the semiconductor switch over to turn the thyristor on at a large firing angle resulting in a current flowing through a load. Then the semiconductor switch is heated by a heating resistor connected across the load to decrease in the break-over voltage to decrease the firing angle of the thyristor until a steady-state current flows through the load.
Inventors
- 👤 Josuke Nakata
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 13:32
CPC Classifications
H; H03; H03K; H03K17/00; H03K17/51; H03K17/56; H03K17/72; H03K17/725
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
115 words
A circuit for soft-starting an electric load, comprising, in combination, thyristor means serially connected to an electric load across a source of alternating current, circuit means including a capacitor connected to said source and a semiconductor thermally sensitive switch element having a breakover voltage decreased with an increase in temperature, said circuit means being operative to trigger said thyristor in response to said break-over of said semiconductor thermally sensitive switch element due to a voltage across said capacitor exceeding said break-over voltage of said semiconductor thermally sensitive switch element, and electric heater means thermally coupled to said semiconductor thermally sensitive switch element to be electrically energized during a flow of load current through said load.
Claim 2
Dependent Claim
115 words
A circuit for soft-starting an electric load, comprising, in combination, thyristor means serially connected to an electric load across a source of alternating current, circuit means including a capacitor connected to said source and a semiconductor thermally sensitive switch element having a breakover voltage decreased with an increase in temperature, said circuit means being operative to trigger said thyristor in response to said break-over of said semiconductor thermally sensitive switch element due to a voltage across said capacitor exceeding said break-over voltage of said semiconductor thermally sensitive switch element, and electric heater means thermally coupled to said semiconductor thermally sensitive switch element to be electrically energized during a flow of load current through said load.
Claim 3
Dependent Claim
27 words
A circuit for soft-starting an electric load as claimed in claim 1, wherein said electric heater means is energized with a current proportional to said load current.
Claim 4
Dependent Claim
32 words
A circuit for soft-starting an electric load as claimed in claim 1 wherein said capacitor in said circuit means is serially connected to a variable resistor across said source of alternating current.
Claim 5
Dependent Claim
41 words
A circuit for soft-starting an electric load as claimed in claim 1 wherein said thyristor means is a bidirectional thyristor and said semiconductor thermally sensitive element is a semiconductor element capable of being broken over in each of the opposite directions.
Claim 6
Dependent Claim
24 words
A circuit for soft-starting an electric load as claimed in claim 2 wherein said electric heater means is connected in parallel to said load.
Claim 7
Dependent Claim
48 words
A circuit for soft-starting an electric load as claimed in claim 4 wherein said semiconductor thermally sensitive switch element includes three semiconductor layers of alternate conductivity type difining two P-N junctions, and said electric heater means is positioned to change a temperature at each of said P-N junctions.
Claim 8
Dependent Claim
44 words
A circuit for soft-starting an electric load as claimed in claim 4 wherein said semiconductor thermally sensitive switch element is a bidirectional thyristor including four P-N junctions and said electric heater means is positioned to change a temperature at each of said P-N junctions.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-07-21 | 1979-01-20 | 1979-07-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-07-21 | 1983-01-20 | 1983-07-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-07-21 | 1987-01-20 | 1987-07-22 | $7700.00 | Window Closed / Lapsed |