代写Session 2 – DC motors代写留学生Matlab语言程序

Session 2 - DC motors

DC motors

Introduction

DC motors are electromechanical devices that use direct current (DC) to convert electrical energy into mechanical energy. There are various types of DC motors, and their classification varies depending on the operating mode, physical construction and/or electrical configuration. Two types of motors will be investigated in this session: permanent magnet and wound-field. The fundamental theory behind these devices has been presented during the lectures and lecture notes can be found in Canvas and in the module pack.

Problem sets

Before the session, complete the following problem sets by hand:

Problem Sheet 3 – Problems E1 to E5 (Page 21 from the Module pack)

Pre-work

Before the session, read the exercises that will be simulated during the session and make sure to understand them.

Using the background theory and numerical analysis, solve the problems by hand. The results obtained from this numerical analysis usually help to know if the simulation parameters have been set-up properly. (Hint: this good practice is also important when carrying out practical experiments and/or testing)

Exercise 1 - Permanent Magnet DC motor

The aim of this exercise is to simulate a Permanent Magnet DC motor in Simscape, and to test the operating conditions and parameters of the motor.

Figure 1 shows the schematic of DC voltage source powering a DC motor in Simulink using Simscape blocks. The DC motor is connected to a mechanical load. Note that the motor block consists of two parts, an electrical part (in blue) and a mechanical part (in green); both sides of the system must be ‘grounded’ or use a fixed reference point.

Figure 1 – Schematic of a DC voltage source powering a permanent magnet DC motor.

Implement the schematic shown in Figure 1 of a permanent magnet DC motor without mechanical load (e.g. set the torque to zero). Using the information provided in Table 1 obtain the motor parameters and working conditions and configure the motor in the model for testing. For this section, a different motor specification is allocated depending on the second to last digit of your candidate number (AAAAYA), so if your candidate number is 037895 the value of Y would be 9. Note that some parameters are added to provide physical characteristics of the motor (e.g. inductance, inertia) but these are not normally considered in the constant speed (steady-state) analysis of the motor, however they provide key information about the transient operation.

Table 1 – Permanent Magnet DC motor physical parameters.

Test the motor for the no-load conditions. Note: To configure the motor the motor constant must be calculated beforehand.

Update the model created earlier to include a mechanical load (e.g. set the torque value to the rated torque provided) and perform. a full-load test using the information provided in Table 1. To measure mechanical torque, and be able to calculate mechanical output power, an Ideal Torque Sensor must be added to the system. See Figure 1 as guidance to integrate such sensor including how to calculate mechanical output power.

Results

Test and validate:

No-load and full-load speed plots

No-load and full-load voltages

No-load and full-load current plots

Input and output power at full load

Motor Efficiency at full load

Table 2 – Comparison of simulation and theoretical results for exercise 1.

The motor parameters given in Table 2 are the corresponding parameters of motors available from well-known DC motor manufacturers. Simscape has integrated a compilation of real-world motors into a database so these  can be used within the simulation environment.

To add the manufacturer’s motor specifications into the simulation, double-click on the DC motor block, then click on the ‘Value’ from the ‘Selected part’ setting (a new window will open). This window contains a vast selection of permanent magnet DC motors. Using the information provided in Table 2 find the corresponding   motor, select it and on the top-left corner of the window click ‘Apply all’, this window can be closed now. For this section, a different motor specification is allocated depending on the second to last digit of your candidate number (AAAAYA), so if your candidate number is 037895 the value of Y would be 9.

Table 3 – Permanent Magnet DC motor manufacturer and rated parameters.

Using the more detailed model provided by the manufacturer, repeat the previous no-load and full-load test with this motor. Note: There is no need to repeat the theoretical analysis since the motor parameters are the same as those in Table 1.

Results

Test and validate:

No-load and full-load speed

No-load and full-load voltages

No-load and full-load current

Input and output power at full load Motor Efficiency at full load

Note: There is no need to include these plots in the portfolio, but the results must be compared to those from Table 2.

Table 4 – Comparison of simulation and theoretical results for exercise 1 using manufacturer parameters.

Exercise 2 - Wound-field DC motor (Separately excited)

The aim of this exercise is to simulate a separately excited wound-field DC motor in Simscape, and to test the operating conditions and parameters of the motor.

Figure 2 shows the schematic of a separately excited wound-field DC motor powered by two independent DC voltage sources. The motor is connected to a mechanical load and the relevant instrumentation has been included to collect data.

Figure 2 – Schematic a separately excited wound-field DC motor with mechanical load.

To enable the separately excited wound-field DC motor, double-click on the ‘standard’ DC Motor block in Simscape, and on the ‘Field type’ select ‘Wound’ .

Table 5 shows the motor specification and physical parameters provided by the manufacturer. Use this data to implement the model shown in Figure 2 for testing.

Table 5 – Nidec wound-field DC motors parameters and specifications.

Results

Test and validate:

No-load speed

No-load current signal

Full-load speed signal

Full-load current signal

Excitation power

Input and output power

Motor Efficiency

Table 6 – Comparison of simulation and theoretical results, and manufacturer’s specifications for the separately excited wound-field motor from exercise 2.

Exercise 3 - Shunt DC motor

The aim of this exercise is to simulate a shunt DC motor in Simscape, and to test the operating conditions and parameters of the motor.

Figure 3 shows the schematic of a shunt DC motor powered by a DC voltage source. The motor is connected to a mechanical load and the relevant instrumentation has been included to collect data. As shown in Figure 3, Simscape has a specific block representing the shunt motor configuration (see Assignment Brief Portfolio).

Figure 3 – Schematic a shunt DC motor with mechanical load.

Using the information provided in Table 5 about the Nidec would-field DC motors, implement and configure the motor model as shown in Figure 3 and add the appropriate instrumentation. Notice that in the shunt configuration the field and the armature are supplied with the same voltage, in this case, make the voltage  supplied to be the same as that to the ‘field excitation voltage’ from the previous exercise. Note: While the physical parameters of the motor remain the same, a new ‘no-load’ speed must be calculated.

For this test, configure the motor using the ‘By equivalent circuit parameters’ within the block settings. Note that the Back-emf constant in this block has V*s/(A*rad) units, by checking the documentation in Mathworks Help Centre see that vb  = Lafifw which corresponds to the back emf, compared to the notes from the lectures where ea  = Kφfw so comparing these two equations: Kφf   = Laf if. The input parameter required as the back- emf constant in this block is Laf.

Results

Test and validate:

No-load speed

No-load current signal

Full-load speed signal

Full-load current signal

Input and output power

Motor Efficiency

Table 7 – Comparison of simulation and theoretical results, and manufacturer’s specifications for the shunt motor from exercise 3.

Exercise 4 - Series (Universal) DC motor

The aim of this exercise is to simulate a series (universal) DC motor in  Simscape, and to test the operating conditions and parameters of the motor. To achieve this, the block shown in Figure S2E5.1 will be required.

Figure 4 shows the schematic of a series DC motor powered by a DC voltage source. The motor is connected to a mechanical load and the relevant instrumentation has been included to collect data. Using the details from Table 8 and the datasheet provided in Canvas, implement and configure the electromechanical system for the series DC motor. Note: It is recommended to configure the series (universal) motor using the ‘By DC rated power, rated speed & electrical power’ parametrisation. For this section, a different motor specification is allocated depending on the second to last digit of your candidate number (AAAAYA), so if your candidate number is 037895 the value of Y would be 9.

 

Figure 4 – Schematic a series DC motor with mechanical load.

Table 8 – Nidec series motor models to be tested in exercise 4.

Results

Test and validate:

No-load speed

No-load current signal

Full-load speed signal

Full-load current signal

Input and output power

Motor Efficiency

Table 8 – Comparison of simulation and theoretical results, and manufacturer’s specifications for the series motor from exercise 4.

Exercise 5 - Speed vs Torque in various DC motor configurations

For all motor configurations analysed in this session (e.g. Permanent Magnet, Separately Excited, Shunt, and     Series) produce a Speed vs Torque plot. Use at least 10 load points that go from no-load conditions up to full-   load conditions. Note: For the best comparison, plot the normalised values for all motors in the same plot. This might require some data conversion.

Results

Test and validate:

Speed vs Torque behaviour

Discussion

Write a concise discussion (e.g. one page) about these analytical, simulation and applications problems, that demonstrates knowledge and critical understanding of the operation of dc motors, dc motor configurations, mathematical modelling, electrical circuit modelling, obtained results, simulation capabilities of Simscape, dc motor tests, and dc motor applications.

Reflection

How  did  the pre-work  activities  help  you prepare  to  better  understand  the  theory  and  validate  the simulations?

What were some of the challenges you discovered along the way?

How well did you do with self-organisation, self-learning, and independence?

This section  contains  optional exercises  that  could help  test understanding  of the subject, simscape, and engineering applications. Note that these exercises are only considered if all compulsory exercises are submitted and solved in full.

Exercise 6 (optional) - Speed control of a separately excited DC motor

There are two options to control/adjust the speed of a separately excited DC motor, such as the one presented in exercise 2; by adjusting the magnetic field or by adjusting the voltage supplied to the armature. Using the information in Table 10 analyse and test the two open-loop motor speed control methods. For this section, a different adjustment is allocated depending on the last digit of your candidate number (AAAAAX), so if your candidate number is 037895 the value of X would be 5. Note that a negative reduction is the same as an increment, and a negative increment is the same as a reduction.

Table 10 – Speed control testing conditions using field reduction or armature voltage increase.

Results

Test and validate:

Full-load speed signal Full-load current signal Input and output power Motor Efficiency

Exercise 7 (optional) - Series motor operating in AC

Series motors are also named universal motors since they can operate both in DC and AC. Figure 5 shows the schematic of a series DC motor power by an AC voltage source. Modify the model implemented earlier to operate in AC as shown in Figure 5. Compare the results to those obtained in exercise 4.

Figure 5 – Schematic a series DC motor with mechanical load operating under AC voltage.

Results

Test and validate:

No-load speed

No-load current signal

Full-load speed signal

Full-load current signal

Input and output power

Motor Efficiency