Lab5_handout - DalTech — Dalhousie University Department...

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Unformatted text preview: DalTech — Dalhousie University Department of Electrical :3: Computer Engineering Electrical Machines laboratory ECED 3100 — Lab 5 — Synchronous Motors Object: To become familiar with some aspects of synchronous machine behavior Eguipmant: Lab-Volt Station Strohoscope Synchronous Machine Instrumentation DC Motor Electrodynomcmeter WatWAr Transducer Introduction: Synchronous motors come in two basic forms: 1) The cylindrical rotor and 2) The salient pole rotor. Figure I shows the basic shapes. The cylindrical rotor has a constant air gap and is used primarily for high speed (rs-36052} rpm) motor and generator applications. The salient pole rotor has an air gap of varying length depending on the position of the rotor. This feature helps to increase the motors ability to take and hold a load. These are used for low speed (cSfiflfl rpm) applications and are the more common design. Both of these constructions have a field winding on the rotor which becomes and elcctro-ruaguct which locks in with the rotating field to provide synchronous action- Procedure: 1 JG Generator Mode Li Drive the rotor of the synchronous machine by a DC shunt connected motor at 1am rmp. Using the variable DC supply,_apply {and measure) a field current to the field winding of the synchronous machine. For several values of field current (UFDJSA DC), pleasure the line to neutral voltage Wed at the terminals of a wye connected stator win mg. Plot this voltage as a. function of field current. W? 1.2. Verify that the frequency of the stator voltage is a function of spEd according to the relationship: ' Ns = 1213 HP 2.0 Synchronization 2.1 Remove wiring to the DC shunt motor and shift the hplt drive ethe Water. Set field switch 5 to the off (U) position. Connect Set 5 dgnarnometer to a 120 V 150 Hz supply e strobosco to line triggering (liner'eitt input} and shine it on the rotor of the synchronous machine. Apply 203 v. three phase. 60 Ha power to the w_ve connected stator winding. Apply a small (i212 N»m) load to the motor and observe that the strohoscope gives the appearance of a slowly rotating shaft (it is still spinning at approximately 1300 rpm; DD NOT TRY TO TOUCH THE SW. What you are seeing is the slip. Adjust the DC voitage control knob to about 20% of its travel and engage the field switch. Dbscrve the synchronization process. Increase the load until the motor looses synchronization and then reduce the load. 3J2} Motor Behavior with Constant Field Excitation 3.1 3.2 Set the field current to_ [LS A and the load to zero N-m. With the help of the strobe light, adjust the an gic measurement device to zero degrees. Increase the motor load (0— 1.2 N—m) in steps. Record the motor speed. stator voltage and current, input power (real and reactive) and torque ang]e for each step. Calculate the motor efficiency and power factor at each step and plot the output power as a function of torque angle. Repeat sections 3.1 for a field current of £125 A DC. 4.0 , Motor Behavior with Constant Load 41 4.2 Cylindrical rotor Synchronous motor (4-Po1ei At a load of 0.4 N—m. var}r the field current in steps {ISL-1.0 A DC) and record the motor speed. stator voltage and current. input power (real and reactive) and torque angle for each step. Plot the armamre current as a function of field current. Why does it do this? Plot real and reactive power (P and Q) as a function of field current. What is happening at Q = D? Plot P as a function of Q. Repeat section 4.1 for a load of 0.3 N-m. (Be careful no to exceed the machine ratings) Plot your curves on the same graphs as section 4.1. u . 5e11ent.Pn1e Synchronous Motor (4iPn1ei ...
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This note was uploaded on 12/16/2009 for the course ECED ECED 3100 taught by Professor Little during the Winter '09 term at Dalhousie.

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Lab5_handout - DalTech — Dalhousie University Department...

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