Controller for starting and stopping electric motors
CA 2028476 C · Owner: Merrison, John C. · Inventors: Merrison, John C.; Unsworth, Peter J.; Rowan, Timothy M.
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
A three-phase motor is operated by a controller having sets of thyristors which when triggered switch electricity from each phase of a supply to the motor. The controller measures the interval .PHI. between when the voltage and the current for one phase to the motor make zero crossings and measures the interval .gamma. that the thyristor are non-conductive during half-cycle of the voltage for the one phase. A control angle .THETA. is calculated according to the equation .THETA. = .PHI. + K.gamma. where K is a positive number. The control angle .THETA. is compared to a reference value to derive an error value. The times at which the thyristors are triggered is controlled in response to the …
Read the whole patent
Listed from its CIPO record in Patent Yard's archive of Canadian patents past their term. Its claims, description and drawings are in the CIPO record and on Google Patents, and the Claude kit works from them.
Why it's free to use
- Filed October 24, 1990 and granted January 11, 2000. A Canadian patent filed from October 1, 1989 lasts 20 years from filing, so its term ended October 24, 2010.
- A certificate of supplementary protection adds at most two years for a drug, so even that would have ended by October 24, 2012.
- We check Canadian rights only. A patent in its family in another country could still be in force: check its family on Google Patents.
Timeline
Timeline From CIPO dates
Sources & verification
Official CIPO records
Everything on this page comes from the CIPO record linked above. Contains information licensed under the Open Government Licence – Canada.