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US 4,887,018 AGranted
Line to line to line to neutral converter
AssigneeSquare D Company
InventorJames T. Libert
Life of this patent
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AssigneeSquare D Company
InventorJames T. Libert
Estimating the term…
A reduced voltage starter for gradually starting a polyphase motor having an acceleration control circuit for gradually applying power to the motor and detector circuits for detecting various fault conditions for terminating power to the motor. A shorted solid state switch detector senses when one of the semiconductor switches applying power to the motor is shorted to terminate the application of power from the remaining phases. A phase angle control circuit insures a uniform application of power to the motor. A phase rotation detection circuit detects when the three phases are in other than their correct sequence and terminates power in the event of such detection. An underload detection circuit senses when the current drops beneath a preselected reference after the motor has reached its full speed and terminates power in response to such detection. A line-to-line-to-line-to-neutral convertor produces signals representative of the line-to-neutral voltages which are necessary for other circuit functions.
In a reduced voltage starter having a semiconductor switch circuit for controlling the application of power to a motor from a three phase power source, each phase of said three phase source having a phase adjacent thereto which, in turn, is adjacent to a remaining phase, a line-to-line to line-to-neutral converter, comprising:
The apparatus as in claim 30 wherein said first resistor (R1), said fourth resistor (R2), and said seventh resistor (R3) have substantially the same resistance of a predetermined value:
Dependencies are inferred from the claim text.