US3597671A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Motor speed system with switching frequency control
Assignee: ZF International UK Ltd
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Filing: 1969-07-10
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Granted: 1971-08-03
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Expires: 1989-07-10
Abstract
Abstract An electric traction system and a drive motor, an electronic switching device in series with the motor for controlling current flow through the motor, and a switching circuit for turning the device off at a first current level in the motor and on at the second lower current level in the motor. Manually operable means varies at least one of the current levels for controlling the speed of the motor, and frequency detecting means is provided for detecting the switching frequency and adjusting at least one of the current levels independently of the manually operable means to maintain the switching frequency below a predetermined value.
Inventors
- 👤 Derek Stanley Adams
- 👤 Michael Ainley Thompson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 20:06
CPC Classifications
H; H02; H02M; H02M3/00; H02M3/02; H02M3/04; H02M3/10; H02M3/125; H02M3/135; B; B60; B60L; B60L50/00; B60L50/50; B60L50/52; H02P; H02P7/00; H02P7/06; H02P7/18; H02P7/24; H02P7/28; H02P7/285; H02P7/29; Y; Y02; Y02T; Y02T10/00; Y02T10/60; Y02T10/64; Y02T10/70; Y10; Y10S; Y10S388/00; Y10S388/90; Y10S388/903; Y10S388/907; Y10S388/916; Y10S388/917
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
160 words
An electric traction system comprising in combination a drive motor, an electronic switching device, means connecting said switching device in series with said motor for controlling current flow through said motor, current-sensing means associated with said motor for detecting the level of current flow therethrough, a switching circuit coupled to said current-sensing means and operable to turn said switching device off at a first current level in said motor and to turn said switching device on at a second, lower current level in said motor, whereby said device switches at a frequency dependent on said first and second current levels, manually operable means for varying at least one of said current levels to control the speed of the motor, and also very said switching frequency, and frequency-detecting means for detecting the switching frequency of said device and adjusting at least one of said current levels, independently of the manually operable means to maintain the switching frequency below a predetermined value.
Claim 2
Dependent Claim
160 words
An electric traction system comprising in combination a drive motor, an electronic switching device, means connecting said switching device in series with said motor for controlling current flow through said motor, current-sensing means associated with said motor for detecting the level of current flow therethrough, a switching circuit coupled to said current-sensing means and operable to turn said switching device off at a first current level in said motor and to turn said switching device on at a second, lower current level in said motor, whereby said device switches at a frequency dependent on said first and second current levels, manually operable means for varying at least one of said current levels to control the speed of the motor, and also very said switching frequency, and frequency-detecting means for detecting the switching frequency of said device and adjusting at least one of said current levels, independently of the manually operable means to maintain the switching frequency below a predetermined value.
Claim 3
Dependent Claim
98 words
A system as claimed in claim 1 in which the switching device is a thyristor and the switching circuit includes a second thyristor and a capacitor connected in series across the first mentioned thyristor, the capacitor charging through the second thyristor when the second thyristor conducts and the second thyristor turning off when the capacitor is charged, means being provided for reversing the charge across said capacitors when the second thyristor is off and the first thyristor being turned on by a pulse at its gate and off by a pulse at the gate of the second thyristor.
Claim 4
Dependent Claim
25 words
A system as claimed in claim 2 in which the frequency-detecting means modifies the action of said switching circuit to reduce the lower current level.
Claim 5
Dependent Claim
31 words
A system as claimed in claim 2 in which the manually operable means operates the switching circuit through a contact network which controls acceleration to ensure satisfactory switching of the thyristors.
Claim 6
Dependent Claim
36 words
A system as claimed in claim 2 including means for limiting the minimum off period of the first thyristor to a value sufficient to enable the capacitor to charge and the second thyristor to turn off.
Claim 7
Dependent Claim
73 words
A system as claimed in claim 2 including a third thyristor and an inductor connected across the capacitor, a third thyristor being fired at the same time as the first thyristor to reverse the charge across the capacitor, and the system including means for limiting the minimum on time of the first thyristor to a value sufficient to enable the charge on the capacitor to reverse and the third thyristor to turn off.
Claim 8
Dependent Claim
41 words
A system as claimed in claim 2 including timing means which commences operation when the first thyristor is turned on, and a simulates the effect of attaining the upper current level in conditions where the upper current level cannot be attained.
Claim 9
Dependent Claim
34 words
A system as claimed in claim 2 including means operable on initial movement of the manually operable means for supplying firing pulses to the second thyristor only, to ensure that the capacitor is charged.
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) | 1974-08-02 | 1975-02-01 | 1975-08-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-08-02 | 1979-02-01 | 1979-08-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-08-02 | 1983-02-01 | 1983-08-03 | $7700.00 | Window Closed / Lapsed |