Man machine interface for an A-C motor bypass

Details Man machine interface for an A-C motor bypass Man machine interface for an A-C motor bypass

2000-07-19

2001-11-13

Ro, Bentsu (Department: 2837)

Electricity: motive power systems

Automatic and/or with time-delay means

With nonautomatic control means

C318S454000, C307S039000, C307S040000

Reexamination Certificate

active

06316896

ABSTRACT:

1. FIELD OF THE INVENTION
This invention relates to an A-C motor bypass and more particularly to the man machine interface in such a bypass.
2. DESCRIPTION OF THE PRIOR ART
A-C motors are used in many applications including heating, ventilation and air conditioning and also to drive pumps and fans. Typically the A-C motor is driven by a bypass that is connected between the source of A-C power and the motor. The bypass includes an electronic inverter, which under normal conditions provides power to the motor and controls the speed thereof based on load. The bypass also includes two or three contactors. In the event of an inverter malfunction, the bypass opens a contactor, known either as the drive or inverter contactor (the terms “drive” and “inverter” are used interchangeably herein to refer that contactor), which disconnects the inverter from the load motor and closes another contactor, known as the bypass contactor, which connects the motor to the AC powerline. This feature of bypass is needed when a process is deemed critical and cannot be interrupted due to an inverter failure.
Bypasses have typically used discrete pilot devices, such as incandescent lamps and transformers, and push buttons that are wired in such a way as to perform the logical operation of the unit. This method of controlling the bypass becomes a time consuming task as each wire needs to be properly run and terminated. Furthermore the prices of the pilot devices add cost to the complete design. In addition, such a design does not have any flexibility and intelligence, and is large in size.
Therefore it is desired to provide a man machine interface in a bypass which is relatively inexpensive to make and assemble, and is small in size and has both flexibility and intelligence.
SUMMARY OF THE INVENTION
A bypass for an A-C motor. The bypass has an inverter. The bypass operates in a first mode in which the inverter provides power to the motor and a second mode in which the inverter does not provide power to the motor. The bypass also has firrst and second contactors. The first contactor is closed and the second contactor open when the bypass is operating in the first mode. The bypass further has a first state machine that has a closed loop which has a predetermined total number of states. The first state machine is in a first state when the first contactor is closed and the second contactor is open. The state machine enters a second state when the first state machine determines that one of a predetermined number of events the occurrence of which will result in the opening of the first contactor has occurred. The second state has a predetermined period of time for which the occurring one of the predetermined number of events must continue before the first state machine enters a third state wherein first contactor is opened to thereby stop the motor.


REFERENCES:
patent: 4521845 (1985-06-01), Schwefel
patent: 5619453 (1997-04-01), Roohparvar et al.
patent: 5949251 (1999-09-01), Chambers
patent: 6160365 (2000-12-01), Younger et al.

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