Variable speed control of multiple motors

• US 6,659,726 B2
• Filed: 12/02/2002
• Issued: 12/09/2003
• Est. Priority Date: 12/31/2001
• Status: Active Grant

• Current Assignee: Carrier Corporation (Carrier Global Corporation)
• Original Assignee: Carrier Corporation (Carrier Global Corporation)
• Inventors: Holden, Steve
• Primary Examiner(s): Tyler, Cheryl J.
• Assistant Examiner(s): Rodriguez, William H.
• Application Number:
  US10/307,689
• Publication Number:
  US 20030123989A1
• Time in Patent Office: 372 Days
• Field of Search: 417/2, 417/3, 417/426, 417/429
• US Class Current: 417/2
• CPC Class Codes: F04B 2203/0209 Rotational speed
• CPC Class Codes: F04B 41/06 Combinations of two or more pumps
• CPC Class Codes: F04B 49/20 by changing the driving speed
• CPC Class Codes: F04C 28/02 specially adapted for several pumps connected in series or in parallel
• CPC Class Codes: F04C 28/06 specially adapted for stopping, starting, idling or no-load operation
• CPC Class Codes: F04C 28/08 characterised by varying the rotational speed
• CPC Class Codes: F25B 2400/075 with parallel compressors
• CPC Class Codes: F25B 2600/021 Inverters therefor
• CPC Class Codes: F25B 2600/0251 with on-off operation
• CPC Class Codes: F25B 49/025 Motor control arrangements
• CPC Class Codes: H02P 5/74 controlling two or more ac dynamo-electric motors H02P5/46, H02P5/60 take precedence
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

A system for variable speed control of a plurality of motors under variable load demand is provided. The system includes a constant power source and a plurality of motors having electrical circuits with switches to connect with the constant power source. The system further includes a variable speed drive for driving each of the plurality of motors at variable speed, wherein each of the plurality of motors includes a switch to connect with the variable speed drive. Each of the plurality of motors is selectively electrically connected with the variable speed drive and the constant power source via the switches, for driving the each of the plurality of motors at one of variable and constant speed in response to load demands. To prevent short cycling of the motors under situations of increasing system demand, the control algorithm for the electrical switches provides hysteresis by overspeeding one of the motors before switching from variable speed mode to constant speed mode. Similarly, hysteresis is included in the control algorithm to prevent short cycling of the motors under situations of decreasing system demand.

Claims

1. A system for variable speed control of motors under variable load demand, comprising:

a constant power source;

a plurality of motors connected with said constant power source and having an electric circuit, wherein each of said motors operates in at least one of constant speed mode and in variable speed mode;

means for driving at least one of said plurality of motors in said variable speed mode, wherein each of said plurality of motors is connected with said means for driving through said electric circuit;

each of said plurality of motors selectively electrically connected with said means for driving and said constant power for driving said each of said plurality of motors at one of variable and constant speed in response to system load demands;

control of said electric circuit includes hysteresis when switching from variable speed mode to constant speed mode; and

control of said electric circuit includes hysteresis when switching from constant speed mode to variable speed mode.

2. The system according to claim 1, wherein said means for driving is a single variable speed drive.

3. The system according to claim 2, wherein said means for driving is electrically connected with only one of said plurality of motors at a time.

4. The system according to claim 3, wherein each of said plurality of motors which is not electrically connected with said variable speed drive is electrically connected with said constant power source or is disconnected from all power sources.

5. The system according to claim 1, wherein each of said plurality of motors powers a compressor of one of an air conditioning and refrigeration system.

6. The system according to claim 5, wherein said means for driving is a single variable speed drive.

7. The system according to claim 6, wherein said means for driving is electrically connected with only one of said plurality of motors at a time.

8. The system according to claim 7, wherein each of said plurality of motors which is not electrically connected with said variable speed drive is electrically connected with said constant power source or is disconnected from all power sources.