cogging torque measurement

4
Cogging torque – Measurement method Cogging torque definition: Cogging torque is produced in a permanerit niagnet macliine by tlie magnetic attractioii between the rotor mounted permanent magnets and tlie stator. What is need to measure cogging torque: permanent magnet synchronous generator, external motor, inverter or pulleys, encoder (for rotor angle), torque transducer ( piezo electric reaction torque sensors). [extra equipment: LABVIEW data acquisition, output voltage waveform of generator] -To measure the cogging torque the rotor should turn without any input current -to decrease the rotational speed we can use: - an invertor; - or a a pulley on rotor and one on external motor connected with a flexible rubber ; - Position is measured by an encoder

Upload: ion-trifu

Post on 30-Oct-2014

110 views

Category:

Documents


2 download

TRANSCRIPT

Page 1: Cogging Torque Measurement

Cogging torque – Measurement method

Cogging torque definition:

Cogging torque is produced in a permanerit niagnet macliine by tlie magnetic attractioii between the rotor mounted permanent magnets and tlie stator.

What is need to measure cogging torque: permanent magnet synchronous generator, external motor, inverter or pulleys, encoder (for rotor angle), torque transducer ( piezo electric reaction torque sensors). [extra equipment: LABVIEW data acquisition, output voltage waveform of generator]

-To measure the cogging torque the rotor should turn without any input current

-to decrease the rotational speed we can use: - an invertor;

- or a a pulley on rotor and one on external motor connected with a flexible rubber ;

- Position is measured by an encoder

Figure 1: Setup 1 for measuring the cogging torque.

Page 2: Cogging Torque Measurement

Figure 2: Setup 2 for measuring the cogging torque.

- The position of the axle is measured with a 12-bit (4096 states), gray code, absolute encoder.

- The torque is measured with piezo electric reaction torque sensors. An eddy currentbrake is installed to apply different torque set points.

- The defined set points are 1,2,3,4 and 5 Nm and 0.5, 0.6, 0.7, 0.8, 0.9 and 1.0 Hz. Thisprovides a mesh which consists of 30 measurements. Data acquisition is done with the help of Labview.

Dynamic measurementMost motor measurement equipment is configured for measurements while the motoris rotating. As such, it is attractive to attempt cogging torque measurement while themotor is rotating. This form of measurement is discussed by Holtz and Springob [37]and by Bianchi and Bolognani [5]. As an in-line torque sensor was used, both authorspointed out the need for keeping rotor speed constant during the measurements.

It will be great if can be tested:- At least 2 rotors with diferent number of poles- At least 2 stators/rotors with diferent skew angles- A rotor that can support pole shifting (mounted surface magnets or with interior

magnets)

Page 3: Cogging Torque Measurement

Generator with interior magnets that support pole shifting (angle between magnets)

Generator with surface mounted magnets that support pole shifting (angle between magnets)

References:[1] Cogging Torque Measurement, Moment of Inertia Determination and Sensitivity Analysis of an Axial Flux Permanent Magnet AC motor, P.W. Poels, DCT 2007.147[2] Efficient eolian-solar systems , Tiberiu Tudorache