Method of limiting current in a DC motor and DC motor system for implementing said method
AssigneePapst-Motoren GmbH & Co. KG
InventorsHermann Rappenecker, Roland Dieterle
Life of this patent
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Abstract
The invention relates to a method of current limitation in a direct current motor, with the following steps: in successive cycles, the motor is turned on at a predetermined place in the cycle and, after lapse of a predetermined time interval, the motor current is tested in a first test and, if found to be too high, the current is shut off; after lapse of another interval measured from the first test, the motor current is tested again during the same cycle and, if found to be too high, is shut off if it was not shut off previously; after lapse of a third interval, measured from the second test, the motor current is turned on, insofar as it was shut off at either of the two tests, and the cycle is repeated.
Claims17
A method of current limitation in a direct current motor having a respective switch which controls current flow in a respective winding strand of the stator of the motor, comprising the steps of
- during each of successive operating cycles having an essentially constant duration (T.sub.c) of less than one second,
- switching on motor current (i) at a predetermined instant (t.sub.1) of each cycle;
- checking motor current, with respect to a predetermined limit value, in a first test (S174) performed at a predetermined time interval (.tau.) after said switching on, and interrupting (S176) said current if it exceeds said limit value;
- checking motor current in a second test (S182) performed in the same cycle at a predetermined time interval after said first test, and, insofar as said current is still flowing, interrupting said current if it exceeds a predetermined limit value;
- insofar as said current was interrupted at either of said first and second tests, switching said motor current back on after lapse of a predetermined time interval measured from said second test;
- and
- repeating the foregoing steps in successive cycles.
A method of current limitation in a direct current motor having a respective switch which controls current flow in a respective winding strand of the stator of the motor, comprising the steps of
- during each of successive operating cycles of essentially constant duration (T.sub.c),
- switching on motor current (i) at a predetermined instant (t.sub.1) of each cycle;
- checking motor current, with respect to a predetermined limit value, in a first test (S174) performed at a predetermined time interval (.tau.) after said switching on, and interrupting (S176) said current if it exceeds said limit value;
- checking motor current in a second test (S182) performed in the same cycle at a predetermined time interval after said first test, and, insofar as said current is still flowing, interrupting said current if it exceeds a predetermined limit value;
- insofar as said current was interrupted at either of said first and second tests, switching said motor current back on after lapse of a predetermined time interval measured from said second test;
- and
- repeating the foregoing steps in successive cycles, wherein said duration (T.sub.c) of each cycle is shorter than 100 microseconds, in order to obtain current limitation with a current pulse frequency of at least 10 kHz.
A direct current motor (30) having a control circuit which measures current (i) flowing through said motor and which includes a current limitation circuit (72, 132, 142) which becomes effective when said current exceeds a predetermined limit value, wherein
- the current limitation circuit operates cyclically;
- within each cycle of current control, the circuit performs a first current level test at a first instant (t.sub.2) a predetermined time (.tau.) after a switch-on time (t.sub.1) and, if said current exceeds a predetermined limit value, interrupts the flow of current;
- at a second instant (t.sub.3) within said cycle, a predetermined time interval after said first current level test, the circuit performs a second current level test and, if said current exceeds a predetermined limit value, interrupts the flow of current;
- and
- at a third instant (t.sub.4), a predetermined time interval after said second current level test, the circuit turns motor current back on, if it was previously interrupted, and begins a new operating cycle.
Dependencies are inferred from the claim text.