Apparatus and method for controlling a centrifugal compressor

Claim 2

Apparatus for preventing shutdown of a centrifugal compressor driven by an electric motor during short-term power failures, comprising: a source of electrical power connected to said motor; switch means interposed said power source and said motor; electrically operated switch actuating means connected to said switch means and to said power source, said switch actuating means normally opening said switch means upon power failure; and circuit means electrically interconnecting said switch actuating means and said power source for automatically reactuating said switch means when a power failure is of a duration less than a first pre-determined period and for not actuating said switch means when said power failure is of a duration greater than said pre-determined period and when a second power failure occurs within a second pre-determined time period from the end of an original power failure greater than said first pre-determined time period.

Claim 3

In the method of operating an electric motor driving a centrifugal compressor, wherein said motor is normally connected to a source of electrical power and started through the sequential operation of electrical circuit means initiated by the action of a human operator, and wherein an electrical power supply failure results in a shutdown of said motor requiring human intervention to re-initiate the normal starting sequence, the improvement of automatically restarting said motor after a short time duration power failure, comprising the steps of: a. electrically measuring the time duration of said power failure; b. automatically initiating the sequential operation of said electrical circuit means if said measured time is less than a first pre-selected value to thereby cause said motor to be restarted; c. electrically measuring a second pre-selected time period beginning with the automatic initiation of the sequential operation of said electrical circuit means; and d. inhibiting the automatic initiation of the sequential operation of said electrical circuit means if a power failure occurs during said second pre-selected time period.

Claim 4

In the method of operating an electric motor driving a centrifugal compressor, wherein said motor is normally connected to a source of electrical power and started through the sequential operation of electrical circuit means initiated by the action of a human operator, and wherein an electrical power supply failure results in a shutdown of said motor requiring human intervention to re-initiate the normal starting sequence, the improvement of automatically restarting said motor after a short time duration power failure, comprising the steps of: a. electrically measuring the time duration of said power failure; b. automatically initiating the sequential operation of said electrical circuit means if said measured time is less than a first pre-selected value to thereby cause said motor to be restarted; c. electrically measuring a second pre-selected time period beginning with the automatic initiation of the sequential operation of said electrical circuit means; and d. inhibiting the automatic initiation of the sequential operation of said electrical circuit means if a power failure occurs during said second pre-selected time period.

Claim 5

Apparatus for preventing shutdown of a centrifugal compressor, driven by an electric motor, during short-term power failures, comprising, in combination: a main electrical supply; a safety interlock circuit electrically connected to said main electrical supply for stopping said motor and for monitoring the status of critical components of said compressor and to prevent starting or continued operation of said motor in the event of an abnormal status of any one of said critical components, said safety interlock circuit including a power inlet portion comprising a momentary contact reset switch and a first circuit locking relay contact pair connected in parallel such that electrical power into said safety interlock circuit must flow through either said reset switch or said first circuit locking contact pair and electrical power will not be automatically re-established to said sAfety interlock circuit through said reset switch or said first circuit locking contact pair when electrical power is re-established after an electrical power failure; a motor starter circuit electrically connected to said main electrical supply and said drive motor for transferring electrical current to said motor; an enabling circuit electrically connected to and energized through said safety interlock circuit, said enabling circuit being electrically connected to said motor starter circuit for controlling said motor starter circuit to allow current to flow to said drive motor, said safety interlock circuit and said enabling circuit, upon failure of the main electrical supply, becoming de-energized to thereby open the connection of said main supply to said drive motor to prevent reconnection of said main electrical supply to said motor upon resumption of power to said main electrical supply, said enabling circuit including a power inlet portion comprising a momentary contact start switch and a second circuit locking relay contact pair connected in parallel such that electrical power into said enabling circuit must flow through either said start switch or said second circuit locking contact pair and electrical power will not be automatically re-established to said enabling circuit through said start switch or said second circuit locking contact pair when electrical power is re-established after an electrical power failure; and circuit means connected to said main electrical supply and interconnecting said supply with said safety interlock circuit and said enabling circuit for automatically re-energizing said safety interlock circuit and said enabling circuit when the duration of the failure of said main electrical supply is of a duration less than a pre-determined period to thereby re-establish connection of said main electrical supply to said drive motor, said circuit means including a safety interlock reset circuit connected in parallel with said reset switch and said first circuit locking contact pair for allowing re-energization of said safety interlock circuit after a power failure.

Claim 6

Apparatus for preventing shutdown of a centrifugal compressor, driven by an electric motor, during short-term power failures, comprising, in combination: a main electrical supply; a safety interlock circuit electrically connected to said main electrical supply for stopping said motor and for monitoring the status of critical components of said compressor and to prevent starting or continued operation of said motor in the event of an abnormal status of any one of said critical components, said safety interlock circuit including a power inlet portion comprising a momentary contact reset switch and a first circuit locking relay contact pair connected in parallel such that electrical power into said safety interlock circuit must flow through either said reset switch or said first circuit locking contact pair and electrical power will not be automatically re-established to said sAfety interlock circuit through said reset switch or said first circuit locking contact pair when electrical power is re-established after an electrical power failure; a motor starter circuit electrically connected to said main electrical supply and said drive motor for transferring electrical current to said motor; an enabling circuit electrically connected to and energized through said safety interlock circuit, said enabling circuit being electrically connected to said motor starter circuit for controlling said motor starter circuit to allow current to flow to said drive motor, said safety interlock circuit and said enabling circuit, upon failure of the main electrical supply, becoming de-energized to thereby open the connection of said main supply to said drive motor to prevent reconnection of said main electrical supply to said motor upon resumption of power to said main electrical supply, said enabling circuit including a power inlet portion comprising a momentary contact start switch and a second circuit locking relay contact pair connected in parallel such that electrical power into said enabling circuit must flow through either said start switch or said second circuit locking contact pair and electrical power will not be automatically re-established to said enabling circuit through said start switch or said second circuit locking contact pair when electrical power is re-established after an electrical power failure; and circuit means connected to said main electrical supply and interconnecting said supply with said safety interlock circuit and said enabling circuit for automatically re-energizing said safety interlock circuit and said enabling circuit when the duration of the failure of said main electrical supply is of a duration less than a pre-determined period to thereby re-establish connection of said main electrical supply to said drive motor, said circuit means including a safety interlock reset circuit connected in parallel with said reset switch and said first circuit locking contact pair for allowing re-energization of said safety interlock circuit after a power failure.

Claim 7

The apparatus of claim 3, wherein said circuit means further includes an enabling restart circuit connected in parallel with said start switch and said second circuit locking contact pair for allowing re-energization of said enabling circuit after a power failure.

Claim 8

The apparatus of claim 4, wherein said circuit means further includes a power dip timing circuit electrically connected to said safety interlock restart circuit and said enabling restart circuit.

Claim 9

The apparatus of claim 5, wherein said circuit means further includes a redundant, fail-safe restart circuit electrically connected to said power dip timing circuit and said safety interlock restart circuit.