Experiment No. 1

Experiment Title: Prime Mover Measurement

Submitted by: Euzziel E. Eclarinal

EEC501L/L31/TH/14:00-16:50

Submitted to: Engr. Raymond R. Raguindin

Date submitted: 08/06/2015

Final Data Sheet:

I 1 I 2 I 3 Average

Without DC Excitation 1.4 1.3 1.39 1.36

Minimum DC Excitation 0.6 0.2 0.4 0.4

Maximum DC Excitation 1.1 0.9 0.9 0.96

Setup:

Figure 1

Setup for Three-phase synchronous motor

Figure 2

Tachometer to measure rotational speed of the motor

Final Data Analysis

The first few steps in the procedure identified and showed how to properly connect a

Three-Phase Synchronous Motor/Generator to its respected source, ammeter, and rheostat.

Correct connections yielded to a running Three-Phase Synchronous Motor/Generator. We were

instructed to adjust the rheostat value first at maximum resistance and then at minimum

resistance. Both values correspond to minimal change in current. Minimum DC excitation

yielded far lower current compared to the result done without DC excitation. Maximum DC

excitation gave less difference compared to the process without DC excitation.

We then recorded the position of the rheostat knob of minimum stator current value

which was at approximately 40˚ (this knob position will be the nonnal excitation) further

adjustment creates humming sound and unstable current which might overwork the motor itself.

Using the Tachometer(device used to measure rotational speed), all three current

excitation variations yielded with the same speed or with very minimal discrepancy. To observe

the rotational direction of the generator, we siwtched of the generator to decrease the speed at a

level which we can observe the rorational direction of the generator. At normal circumstances

(following the connections in the procedure), the generator’s direction is at clockwise which

means that the generator at this state runs at positive speed value. Interchanging the input voltage

polarity reverses the rotational speed direction to counter-clockwise which means that at this

state, the generator runs at negative speed value.

Conclusion:

To conclude, the Prime mover generator or Three-Phase Synchronous Motor/Generator is

basically a voltage-to-speed converter. This means that higher voltage yields in faster rotational

speed. Current on the other hand, does not affect the speed at which the motor runs nor the

rotational direction which it rotates which was measured using a tachometer. Voltage source

polarity will change how the generator rotates as we did so on procedure step 8. Varying the DC

excitation was done using the rheostat which changes the resistance which in turn affects the

current flowing through the generator.

Since we could not finish the experiment due to some technical difficulties concerning

with operational status of the machine and measuring device problems, this is the most data we

could conclude.

Review Questions:

1.) How can you reverse the direction of rotation of a synchronous motor?

-direction of the rotation can be reversed by interchanging the source polarity.

2.) What effect does varying the DC incitation have on the stator current of a synchronous

motor?

-it changes the current but does not change the rotational speed and direction at which the

motor runs.

3.) How can you increase the power output of a synchronous motor?

-to change the power output of a synchronous motor, mechanical load should change.

4.) Calculate the developed motor mechanical output power in procedure 16B or 20i

Mechanical output power (hp) =

5.) Calculate the developed motor mechanical output power in procedure 18 or 21 (just prior

to “breakdown”).

Mechanical output power (hp) =

6.) Which torque measuring device is easier to use, the electrodynamometer or the Prony

Brake?

-we did not come this far but since electric device gives better results,

electrodynamometer since it does not rely on fixed weights but on power output of the

motor.

7.) Where is the power (heat) dissipated in the electrodynamometer?

-the rotor at which the motor is in contact with the measuring device,

8.) Where is the power (heat) dissipated in the Prony brake?

-heat dissipated in the brake blocks.