Electricity: motive power systems – Limitation of motor load – current – torque or force
Reexamination Certificate
2000-10-31
2003-03-25
Nappi, Robert E. (Department: 2837)
Electricity: motive power systems
Limitation of motor load, current, torque or force
C318S132000, C318S254100, C318S430000, C318S432000, C318S433000, C388S842000, C388S848000
Reexamination Certificate
active
06538406
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to electric motors and, more particularly, to a system and method for improving the transient speed response of electric motors in the presence of drive current response rate limitations.
Drive systems for variable speed electric motors are often limited in how quickly they can change the speed of the electric motor. This is due to the fact that the rate of change in the drive current needed to effectuate a rapid change in motor speed cannot be achieved due to motor design limitations and/or the lack of an adequate forcing voltage.
U.S. Pat. No. 4,280,081, which is herein incorporated by reference in its entirety, discloses an inertia compensation method to improve the acceleration and deceleration performance of motor drive systems. However, this method, as well as other prior art inertia compensation methods, do not address the limited transient speed response imposed by drive current response rate limitations (hereinafter “current rate limitations”).
BRIEF SUMMARY OF THE INVENTION
In an exemplary embodiment of the invention, a drive system for an electric motor comprises a current reference generator that generates and outputs a current reference based on a speed reference, a current rate limiter that receives the current reference and outputs an adjusted current reference based on available current, a current rate recovery system that determines total accumulated lost current-seconds due to the current rate limiter and outputs current-seconds to be added to the adjusted current reference, and an adder that adds the current-seconds to the adjusted current reference output by the current rate limiter until the total accumulated lost current-seconds are applied to the electric motor.
The invention also provides a current rate recovery system for an electric motor drive system, comprising a comparator that determines a difference between a current reference and an adjusted current reference generated by the electric motor drive system, and an integrator that receives and integrates the difference between the current reference and the adjusted current reference over time, and outputs at least a portion of the integrated difference between the current reference and the adjusted current reference as current-seconds to be added to the adjusted current reference.
The present invention also provides a method of compensating for current-rate limitations in an electric motor drive system, comprising the steps of monitoring total accumulated current-seconds lost due to a lack of available current, and recovering the total accumulated lost current-seconds as sufficient current becomes available.
The present invention keeps track of the total accumulated lost current-seconds due to current rate limitations, and restores the total accumulated lost current-seconds to the system when current becomes available.
REFERENCES:
patent: 3629633 (1971-12-01), O'Callaghan
patent: 3955130 (1976-05-01), Graf
patent: 3983464 (1976-09-01), Peterson
patent: 4028601 (1977-06-01), Peterson
patent: 4152632 (1979-05-01), Peterson
patent: 4280081 (1981-07-01), Dinger et al.
patent: 4322668 (1982-03-01), Trussler et al.
patent: 4605887 (1986-08-01), Boella
patent: 5525877 (1996-06-01), Umida
Duncan Kevin
General Electric Co.
Hunton & Williams
Nappi Robert E.
Smith Tyrone
LandOfFree
System and method for improving transient speed response of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with System and method for improving transient speed response of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and System and method for improving transient speed response of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3085734