Electricity: motive power systems – Induction motor systems – Primary circuit control
Reexamination Certificate
2000-06-28
2001-10-16
Fletcher, Marlon T. (Department: 2837)
Electricity: motive power systems
Induction motor systems
Primary circuit control
C318S434000, C318S773000, C361S023000
Reexamination Certificate
active
06304053
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to motor controllers and more particularly, to a delta motor soft starter that automatically detects when delta motor leads have been swapped and changes firing circuit timing.
BACKGROUND OF THE INVENTION
A delta motor system typically includes a delta motor, a three phase power source, a fault contactor and a motor controller. The motor controller generally includes a set of three control switches that are connected between the line voltage terminals of the three phase power source and the windings of the delta motor. The motor controller regulates the voltage from the three phase power source to the delta motor by selectively opening and closing the three control switches. The proper operation of the delta motor is dependent on the proper regulation of the control switches.
During start up, the controller, also referred to as a soft starter, controls the switches to provide reduced voltage starting until the motor reaches full speed. The motor controller's internal timing mechanisms are specifically designed to regulate the application of specific line voltages from the three phase power source to specific delta motor windings based on a predesignated wiring configuration. Conventional electrical leads are typically used to connect the delta motor windings to the control switches and to the fault contacts. Since the electrical leads providing connection to the delta motor terminals are not always clearly marked, mistakes in wiring the delta motor system are common. If the winding leads are swapped, resulting in the windings being driven relative to different power source phases than required, then the soft starter may not be able to supply a reduced voltage start or may not be able to supply full voltage to the motor after starting. This can also damage the motor and the soft starter.
The present invention is directed to solving one or more of the problems discussed above, in a novel and simple manner.
SUMMARY OF THE INVENTION
It is a principal object of this invention to provide a new and improved motor controller that automatically detects when a delta motor is wired with swapped leads within a motor system. More specifically, it is an object of the invention to provide a motor controller that detects the swapped leads prior to starting the delta motor so that the firing circuit timing can be changed and the delta motor and the motor controller are not subjected to potentially damaging conditions.
An exemplary embodiment of the invention achieves the foregoing objects in a motor controller for use in a motor system including a multiphase power source having three supply lines and a delta motor having three windings.
The motor controller includes a plurality of switching means and a power source detecting means. Each of the switching means is intended to be operatively connected in series with a selected one of the windings and between an associated selected pair of the supply lines. The power source detecting means is operatively connected across each of the switching means to detect if the windings are connected in series with the intended switching means. A control automatically controls the switching of the switching means dependent on whether the windings are connected in series with wherein firing circuit timing of the switch is changed dependent on whether each switch is connected to the first lead of the intended winding or the second lead of the different winding intended switching means.
In one embodiment, the plurality of switching means comprise solid state devices.
In another embodiment, the plurality of switching means comprise SCRs or triacs.
In another form of the invention, the power source detecting means includes a decoding means for detecting the swapped lead condition if the of voltages across each switching means is equal to voltage between an unintended pair of the supply lines.
Other objects and advantages of the invention will become apparent from the following specification taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 5227703 (1993-07-01), Boothe et al.
patent: 5243243 (1993-09-01), Andrews
patent: 5761018 (1998-06-01), Blakely
patent: 5859514 (1999-01-01), Chouffier et al.
patent: 6038114 (2000-03-01), Johnson
patent: 6072674 (2000-06-01), Johnson
patent: 6169383 (2001-01-01), Johnson
Fletcher Marlon T.
Siemens Energy & Automation Inc.
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