English汽车测功拖车

How can such a dynamometer be achieved? Advanced motor controls have been developed for precise torque tracking. These techniques can be applied to a dynamometer for tracking a desired torque-speed profile for real-time load simulation. This dynamometer application is unique in comparsion with servo-type motor controls since the dynamometer will be driven as the load and the torque profile to track will be user input. The motor under test (MUT) will supply the driving torque. It's control, if any, will be independent of the dynamometer control. Note that the dynamometer usually will be in the generating mode, with excursions into the motoring mode during certain events (such as acceleration when the desired load inertia is less than the actual system inertia). Thus the dynamometer proposed in this paper is a new application of a torque tracking problem. The proposed system uses a three-phase induction motor as the loading machine (LM). The LM is mechanically coupled to the h4UT and is electrically connected to power conversion equipment. Minimally, the power converter will need to be twoquadrant, i.e., provide motoring and regeneration in one rotational direction. A four-quadrant converter would be ideal. An induction machine is chosen as the LM due to its robust qualities, easy availability, and it's well-known characteristics. The LM could actually be any type of electric machine that has the capability to be a motor and a generator. The theory developed here can be easily applied to these other devices. Induction machines are typically difficult to precisely control. Thus if they can be applied in this application with success, other machines should be easy to implement. 11. DYNAMOMETER SYSTEM In most situations, a motor can only be tested for steady-state operating characteristics. The motorlload combination will have transient behavior that is a function of the motor, the load, and the coupling between the two. The actual transient behavior is often determined when the motor is used with the "real" load.
E. R. Collins, Jr., Member, IEEE and Y. Huang Department of Electrical and Computer Engineering Clemson University Clemson, SC 29634-0915 USA
Abstract A programmable dynamometer is proposed where the user can define the steady-state and inertial Rotating torque-speed characteristic of the load. machinery can be tested on this dynamometer to determine their transient and steady-state Characteristics with a practical load. The user inputs the desired load characteristics by selecting polynomial and inertia coefficients. The system uses proportional-integral (PI) controllers to control a three-phase induction motor using indirect field orientation. Simulations show that the dynamometer offers excellent tracking of the desired torque-speed characteristic and simplicity of use.
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I. INTRODUCTION
Rotating machines are often tested in the laboratory using a dynamometer, which usually consists of a braking mechanism and a clutch. The brake can be a simple frictional device (e.g., a prony brake) or an electrical generator. The load is adjusted by altering the frictional drag or the electrical output of the generator, or by varying the slip of the clutch. In both cases, the load is passive and the machine under test can only be tested under steady-state loading conditions. Other types of dynamometers use an inertial load. The load inertia is made high enough that the acceleration of the motor/load system is relatively slow; the motor is in quasi steadystate during acceleration. Therefore, the steady-state torque-speed characteristic of the motor is obtained throughout the operating region. Practical loads are active. The inertia of the driven system and forces in the load dictate the load's dynamic performance. A simple brake or inertial dynamometer cannot mimic a practical load. A dynamometer that can imitate a practical load characteristic will require control of the load torque on a continuous basis. This control will be necessary in both steady-state and transient conditions if the actual static and inertial loading characteristics are to be imitated.
94 WM 116-4 EC A paper recommended and approved by the IEEE Electric Machinery Committee of the IEEE Power Engineering Society for presentation at the IEEE/PES 1994 Winter Meeting, New York, January 30 - February 3, 1994. Manuscript submitted August 2, 1993; made available for printing November 29, 1993.
0885-8969/94/$04.00 0 1994 IEEE
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The proposed dynamometer allows one to test a motor with a user-specified torque-speed and inertial characteristic. Many practical loads can be modeled by a polynomial with an inertial term. To demonstrate the capabilities of this dynamometer, the desired load torque will be assumed of the form
IEEE Transactions on Energy Conversion, Vol. 9, No. 3, September 1994
521
A Programmable Dynamometer for Testing Rotating Machinery Using a Three-phase Induction Machine
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Rea a, b, and c are constants, J is the angular moment of inertia of the load and coupling, and a,,, is the rotor's angular rotational speed in rads. The user specifies the constants To, a, b, c, and J; the dynamometer's control system will control the LM such that the LM shaft torque tracks this desired characteristic. The user can easily change the constants to simulate any load torque characteristic within the capabilities of the dynamometer. Thus the MUT can be tested for many types of loads by simply changing the constants of the controller. Note that the control strategy presented in this paper does not limit this approach to only third order polynomials with a constant inertia. The method presented is quite general and can be applied to many hnctions of speed and acceleration. The proposed system is shown in Figure 1. The MUT has friction Om, inertia Jm, and developed torque Tm . The programmable dynamometer's loading machine has actual friction D, and inertia J, and a developed torqueq It is important to note that the developed torques are intemaf torques created by electromagnetic forces on the rotor itself. These torques are not the shaft torques. The response of the overall motorhad system is described by