Load/unload control method for compressor system

Patent metadata

Field	Value
Publication number	US-10451052-B2
Application number	US-201715418326-A
Country	US
Kind code	B2
Filing date	Jan 27, 2017
Priority date	Jan 28, 2016
Publication date	Oct 22, 2019
Grant date	Oct 22, 2019

Abstract

The present disclosure describes a load/unload control method for a compressor system with a rotating compressor connected to a pressure vessel. In the method, the present operating state can be monitored on the basis of a monitored/estimated electrical quantity of the compressor system. The method comprises an identification phase and an operational phase. In the identification phase, the compressor is operated at a constant rotational speed to generate two known pressures to the pressure vessel. At least one electrical quantity is monitored, and values of the electrical quantity corresponding to the pressure limits are stored. In the operational phase, reaching of a pressure limit may then be detected by comparing the present value of the monitored electrical quantity to the stored values.

First claim

The invention claimed is:

1. A load/unload control method for a compressor system comprising a compressor connected to a pressure vessel, a frequency converter controlling an electric motor of the compressor, and means for setting the compressor to either a load mode or an unload mode, wherein the method comprises an identification phase and an operational phase, and wherein the identification phase comprises:
operating the compressor at a known rotational speed of the electric motor to increase pressure inside the pressure vessel while monitoring the pressure and at least one electrical quantity of the compressor system,
determining a first level for the at least one electrical quantity on the basis of the monitored pressure and the at least one electrical quantity, wherein the first level represents a first pressure limit of the pressure inside the pressure vessel,
determining a second level for the at least one electrical quantity on the basis of the monitored pressure and the at least one electrical quantity, wherein the second level represents a second pressure limit of the pressure inside the pressure vessel, and
storing the first level and the second level,

and wherein the operational phase comprises:
operating the compressor al the known rotational speed,
monitoring a present value of the at least one electrical quantity, and
if the present value falls to the first level, setting the compressor to the load mode or, if the present value rises to the second level, setting the compressor to the unload mode.

2. A method according to claim 1 , wherein the monitored electrical quantity is measured or estimated by using the frequency converter.

3. A method according to claim 2 , wherein the monitored electrical quantity is a mechanical power or torque of the electric motor.

4. A method according to any one of claim 1 , wherein the operating of the compressor during the identification phase comprises:
operating the compressor in the load mode to pressurize the pressure vessel in order to determine the second level, and
operating the compressor n the unload mode to depressurize the pressure vessel in order to determine the first level.

5. A method according to claim 4 , wherein the determining of the second level is performed when the compressor operates in the load mode and comprises
detecting a first known pressure inside the pressure vessel and a first value of the at least one electrical quantity corresponding to the first known pressure,
detecting a second known pressure inside the pressure vessel and a second value of the at least one electrical quantity corresponding to the second known pressure,
forming an interpolation function on the basis the first and second known pressure and the first and second value, wherein the interpolation function represents a relation between the pressure inside the pressure vessel and the monitored at least one electrical quantity, and
determining the second level on the basis the interpolation function and the second pressure limit.

6. A method according to claim 4 , wherein the determining of the first level is performed when the compressor operates in the unload mode and comprises
detecting a first known pressure inside the pressure vessel and a first value of the at least one electrical quantity corresponding to the first known pressure,
detecting a second known pressure inside the pressure vessel and a second value of the at least one electrical quantity corresponding to the second known pressure,
forming an interpolation function on the basis the first and second known pressure and the first and second value, wherein the interpolation function represents a relation between the pressure inside the pressure vessel and the monitored at least one electrical quantity, and
determining the first level on the basis the interpolation function and the first pressure limit.

7. A method according to any one of claim 2 , wherein the operating of the compressor during the identification phase comprises:
operating the compressor in the load mode to pressurize the pressure vessel in order to determine the second level, and
operating the compressor in the unload mode to depressurize the pressure vessel in order to determine the first level.

8. A method according to any one of claim 3 , wherein the operating of the compressor during the identification phase comprises:
operating the compressor in the load mode to pressurize the pressure vessel in order to determine the second level, and
operating the compressor in the unload mode to depressurize the pressure vessel in order to determine the first level.

9. A method according to claim 7 , wherein the determining of the second level is performed when the compressor operates in the load mode and comprises
detecting a first known pressure inside the pressure vessel and a first value of the at least one electrical quantity corresponding to the first known pressure,
detecting a second known pressure inside the pressure vessel and a second value of the at least one electrical quantity corresponding to the second known pressure,
forming an interpolation function on the basis the first and second known pressure and the first and second value, wherein the interpolation function represents a relation between the pressure inside the pressure vessel and the monitored at least one electrical quantity, and
determining the second level on the basis the interpolation function and the second pressure limit.

10. A method according to claim 8 , wherein the determining of the second level is performed when the compressor operates in the load mode and comprises
detecting a first known pressure inside the pressure vessel and a first value of the at least one electrical quantity corresponding to the first known pressure,
detecting a second known pressure inside the pressure vessel and a second value of the at least one electrical quantity correspond ng to the second known pressure,
forming an interpolation function n the basis the first and second known pressure and the first and second value, wherein the interpolation function represents a relation between the pressure inside the pressure vessel and the monitored at least one electrical quantity, and
determining the second level on the basis the interpolation function and the second pressure limit.

11. A method according to claim 5 , wherein the determining of the first level is performed when the compressor operates in the unload mode and comprises
detecting a first known pressure inside the pressure vessel and a first value of the at least one electrical quantity corresponding to the first known pressure,
detecting a second known pressure inside the pressure vessel and a second value of the at least one electrical quantity corresponding to the second known pressure,
forming an interpolation function on the basis the first and second known pressure and the first and second value, wherein the interpolation function represents a relation between the pressure inside the pressure vessel and the monitored at least one electrical quantity, and
determining the first level on the basis the interpolation function and the first pressure limit.

12. A method according to claim 7 , wherein the determining of the first level is performed when the compressor operates in the unload mode and comprises
detecting, a first known pressure inside the pressure vessel and a first value of the at least one electrical quantity corresponding to the first known pressure,
detecting a second known pressure inside the pressure vessel and a second value of the at least one electrical quantity corresponding to the second known pressure,
forming an in

Assignees

• Abb Schweiz Ag

Inventors

• Saukko Juha
• Lyyjynen Markku
• Tolvanen Jukka

Classifications

• F04D27/004

  by varying driving speed · CPC title

• F04C2270/035

  Controlled or regulated · CPC title

• F04B2203/0208

  Power · CPC title

• F04C2270/075

  Controlled or regulated · CPC title

• F04B2203/0207

  Torque · CPC title