Electromechanical Drive Control Learning Note 3

First write this week's simulation job. Simulation results: After starting about 3.9 to 4.2 seconds speed will be stable, stable value around 1213r/min (can not reach 1220r/min, because there will always be 0.6 ohm resistance exists), and the upward curve only a few waves.

Simulation Requirements: Motor start simulation requirements combined with the study of the DC motor mechanical characteristics, with modelica design and simulation of a DC motor string resistance Start-up process, the motor working in the rated voltage and rated magnetic flux, using a series of three or four-phase resistor start, the entire starting process armature current can not exceed the rated current of 3 times times. Rated voltage 240V, rated current 16.2A, torque 29.2N.M, rated speed 1220 r/min, moment of inertia 1 kg.m^2, armature resistance 0.6 Ohm, torque constant (rated magnetic flux) 1.8, electromotive force constant (rated magnetic flux) 0.189,

Simulation process:

1. Theoretical part

Because the speed of n can not be mutated, this indicates that the anti-EMF E can not be mutated, so in the switch resistor when the voltage is virtually unchanged at both ends, so the voltage before and after the change to meet the I1*R1=I2*R2, when the formula is extended to the M-class start

where B is the scale factor, for this simulation I use four-segment series resistance start, and let the current value after each resistance value I1 as close as possible to the limit of 48.6A, because the larger current indicates that there will be a larger torque, speed n change speed will be faster, so that faster to achieve stable speed to shorten the start time. In order to maximize the value of I1 I set the value of I2 to a higher b*i2, so I can calculate:

The values of the resistors (in ohms) can be calculated in order of 5.087618856, 2.98142397, 1.747160929, 1.023863544, 0.6 sequentially. So according to the simulation model, the value of R_ad is 4.487618856, 2.38142397, 1.147160929, 0.423863544, 0.

Therefore, only through the program to find the time when the resistance value should be changed, that is, every time the current from I1 down to I2 when the point, and then change the resistance value on it.

Modelica inside Time is divided into two kinds, that is, state events and time events, so we can through the program to allow the current value to reach our request state when the resistance value change, at this time need and Modelica help us figure out the timing of the event, you can also calculate the time point of the event, Then write the program in the form of a time event.

1. Practice Section

Because multiple attempts did not successfully write a model that could be emulated using state events, the last is a time-only event model that was written using Modelica to try different resistor values at once and read the approximate time values from the simulation results. first attached to the model has been error , I hope the teacher can help to see what the problem inside:

Model Motor "A DC motor model"

Type Voltage=real (unit= "V");

Type Current=real (unit= "A");

Type Resistance=real (unit= "Ohm");

Type Speed=real (unit= "r/min");

Type Torque=real (unit= "n.m");

Type Inertia=real (unit= "kg.m^2");

Torque Tm "Torque of the Motor";

Speed n ' Speed of the ' motor ';

Current I "armature";

Voltage u "Voltage Source";

Resistance r_ad "External resistance";

Real c = 0;

Parameter Real J = 1 "total inertia";

Parameter Real R = 0.6 "armature resistance";

Parameter Real Kt = 1.8 "Torque Constant";

Parameter Real Ke = 0.189 "EMF Constant";

Parameter Real Tl = 29.2 "Load Torque";

Parameter Real b=1.706439241;

Initial equation

r_ad=5.087618856;

Equation

TM-TL = J * der (n) * 6.28/60;

tm= Kt * i;

u= i * r_ad + Ke * N;

If time <= 0.1 Then

u = 0;

Else

u = 240;

End If;

If time>0.2 and i<27.7 and Pre (R_AD) >5 then r_ad=2.98142397;

ElseIf time>0.2 and i<27.7 and Pre (R_AD) >2 then r_ad=1.747160929;

ElseIf time>0.2 and i<27.7 and Pre (R_AD) >1.5 then r_ad=1.023863544;

ElseIf time>0.2 and i<27.7 then r_ad=0.6;

else R_ad=pre (R_AD);

End If;

End Motor;

Then we attach the result diagram and the code of the last multiple experiments. It can be seen that the motor 4 seconds tend to smooth, the curve is not small.

The correct model is as follows:

Model Motor1 "An DC motor model"

Type Voltage=real (unit= "V");

Type Current=real (unit= "A");

Type Resistance=real (unit= "Ohm");

Type Speed=real (unit= "r/min");

Type Torque=real (unit= "n.m");

Type Inertia=real (unit= "kg.m^2");

Torque Tm "Torque of the Motor";

Speed n ' Speed of the ' motor ';

Current I "armature";

Voltage u "Voltage Source";

Resistance r_ad "External resistance";

Parameter Real J = 1 "total inertia";

Parameter Real R = 0.6 "armature resistance";

Parameter Real Kt = 1.8 "Torque Constant";

Parameter Real Ke = 0.189 "EMF Constant";

Parameter Real Tl = 29.2 "Load Torque";

Equation

TM-TL = J * der (n) * 6.28/60;

tm= Kt * i;

u= i * (r+r_ad) + Ke * N;

If time <= 0.1 then u = 0;

Else

u = 240;

End If;

If time <= 1.7 then

R_ad = 4.487618856;

ElseIf Time <=2.6 Then

R_ad = 2.38142397;

ElseIf Time <=3.14 Then

R_ad = 1.147160929;

ElseIf Time <=3.455 Then

R_ad = 0.423863544;

Else

R_ad = 0;

End If;

End Motor1;

The image is as follows: (first the image of the current and then the speed of the image)

Current diagram

Speed chart

Study notes:

The fourth chapter of the book on the protagonist when the three-phase asynchronous motor, out of interest in its working principle in the sophomore has had some communication with the physics teacher, so is not unfamiliar, but its working principle of many formulas and details must be at that time do not know, After a cursory look, it is easy to overlook the relationship between the single-phase current and the mixed values of multiphase currents. And the image is also an indispensable tool to analyze its mechanical properties. Can be analogous to the DC motor to learn.

Tesla's story feels like a very mythical, incredibly unusual feeling, but his great inventive ability and the beautiful visions he creates from the AC and the current world give him a very real sense of fascination. In the battle of the currents I saw Edison, who was very different from the imagination. But Edison's obsession with DC power, like all other scholars, insisted that he was right to have a strong sense of xenophobia, but the use of a slightly despicable business means and propaganda still let me be frightened. In the history of electric motors, alternating current electricity seems to be a matter of course in history, but the events of this period have been brought to pass, but in the meantime, it is not easy to make such great progress in human history. And Tesla also found a rare friendship, through the wind and rain. Money doesn't matter anymore. Scientists inventors in the scientific advancement of support and opposition is indeed not a proof of the right and wrong problem, which involves a variety of interests, but attributed to the heart, based on science itself is the right choice.

Electromechanical Drive Control Learning Note 3