Torque-speed curves are emulated with torque measurement based on a load cell arrangement. For testing variable speed electric drives, static load tests.
A Dynamometer Performing Dynamical Emulation of Loads with Non-Linear Friction
P. Sandholdt, E. Ritchie, J.K. Pedersen
R.E. Betz
Department of Electrical Energy Conversion
Department of Electrical and Computer Engineering
Aalborg University, Institute of Energy Technology
The University of Newcastle
Pontoppidanstraede 101, DK-9220 Aalborg East, Denmark
New South Wales, 2308, Australia
Phone: +45 98 15 85 22
@ Fax: +45 98 15 14 11
Phone:+61 049 216026
@ Fax:+61 049 601712
Abstract - A dynamometer capable of emulating linear, non-
actual drive is a four-quadrant commercial drive system
linear and discontinuous loads for rotating systems is described.
utilising a Permanent Magnet Synchronous Machine
The controllable load is produced by a servo drive system.
(PMSM) driven by voltage source inverter using IGBT´s.
Applications for the dynamometer are steady state load tests and dynamical load tests with linear, non-linear or discontinuous loads for testing of electrical machines in variable speed drive systems. The configuration of the dynamometer is presented, together with simulation models and simulation results. The simulated torque and speed time responses show that the dynamometer tracks the required torque with a high degree of accuracy, for both linear, non-linear and discontinuous loads.
The dynamometer and the drive system under test are shown in Fig. 1. In Fig. 1, the drive system under test is speed controlled, while the dynamometer is torque controlled. The inputs to the dynamometer are thus parameters describing the torque-speed characteristic to be emulated, and the input to the drive under test is essentially a speed reference. In this paper, the dynamometer machine and the tested
I. INTRODUCTION This paper describes a dynamic dynamometer for testing electrical machines and variable speed drives. The configuration of the dynamometer, control strategies, and the dynamic linear, non-linear and discontinuous loads are described. Mostly, dynamometers have been used to perform static load tests of electrical machines [1], [2] or of combustion engines [3]. The performance is then evaluated by measuring
machine are identical PMSM machines, and the power converters and control systems are also identical. The couplings connecting the machines and the torque transducer are assumed to be rigid. The nominal power output of the dynamometer machine is 2.7 kW at 4500 rpm. The first quadrant torquespeed region of the machine and its associated drive is shown in Fig. 2. The data for the dynamometer drive system is given in Appendix I.
the torque-speed characteristic, power losses, efficiency, etc. A dynamometer (2 Nm, 8000 rpm) intended for emulation of torque-speed characteristics has been implemented in [4]. Torque-speed curves are emulated with torque measurement based on a load cell arrangement. For testing variable speed electric drives, static load tests are not sufficient, because dynamic or non-linear effects in some loads can be dominant. Therefore a dynamometer for testing of drives should be able to perform dynamical tests, for example by measuring the response from a load torque
Fig. 1: Diagram showing the dynamic dynamometer acting as load for the drive under test.
step or a load torque ramp change. Furthermore the dynamometer is designed to emulate a given load, such that the machine loaded by the dynamometer acts as it would with the real load. As some industrial loads have non-linear and/or discontinuous load characteristics it is often important to emulate those loads to apply more realistic load characteristics. This paper is focussed on the dynamometer emulation of the load torque. The dynamometer system described here is currently being installed at the laboratory for drive systems testing at Aalborg University, Institute of Energy Technology, Dept. of Electrical Energy Conversion.
II. DYNAMOMETER SYSTEM
Fig. 3: Dynamometer torque-speed region shown for the first quadrant, for a 100 (K) temperature rise.
Basically, the dynamometer comprises a controllable load drive with suitable measurement feedbacks and control. The
torque-speed relation which can be written as (3), if any
Model of Permanent Magnet Synchronous Machine
discontinuous friction contributions are neglected. ThereThe electrical equations for the Permanent Magnet Synchronous Machine are given by (1).
fore the desired load torque the dynamometer should emulate should be as shown in (3). (3)
(1)
where
J
0
where
is a constant load torque
T
sign(
)
M
is
a
sign
function
$
(sign(TM 0)=1
and
ud and uq are the terminal voltages in the d,q-reference
sign(TM
