1 Introduction

Induction motors are the most common type of electrical machine used in industry. They have a simple design which means that they are reliable, have a low cost to manufacture and have low maintenance costs. Standardization means that many brands are widely available in standard configurations. As low-cost easily-controlled power-semiconductors have become cheaper, their use has led to efficient, reliable, low-cost control of induction motors. Industrial variable speed drives offer energy savings and improved system operation when compared to fixed speed systems.

1.1 Objectives

The main objective of this first laboratory is the familiarization with the experimental equipment so the equipment can be operated in a safe and controlled manner. This includes the proper setup and configuration of both AC and DC drives and motors used in this lab. As well as how to monitor the operation of the machines using the measurement equipment to familiarize yourself with the steady state no-load and full-load operating conditions, including voltage and current waveforms and measured values, different drive parameters and the speed range.

2 Prelab

Each student must complete a prelab to hand in at the beginning of your laboratory section. You must have completed all actions of the prelab before being allowed to participate in the Lab. The laboratory is usually completed in pairs, so please try and find a partner in the same lab section as you. See the laboratory schedule on eClass to make sure you show up to the correct time and place.

2.1 Prelab Reading

Familiarize yourself with the Safety Information as well as the Power Supplies, Electrical Machines, Variable Speed Drives and Measurement Equipment used in the first Laboratory by viewing the following information:

  • Look at equipment pages to familiarize yourself with the equipment listed below that is used in Lab 1. Note that there are links to the pdf user manuals available.
  • Read over the entire lab manual so you understand what you will be undertaking during the lab.
  • Make sure you print the Results sheet to bring to lab.
  • Read the Safety Page to familarize yourself with the Laboratory Rules and Dangers.

2.2 Pre-lab Questions

  1. Equipment Ratings.
    1. What is the voltage and current rating of the 3 Phase Power Supply in the lab?
    2. For the PLX15 DC Drive what are the Rated Output Power in kW at 460V?
    3. For the PLX15 DC Drive what is the Maximum Continuous Current in amps for both the input AC and output DC?
    4. for the Baldor PMDC Machine what are the Name Plate ratings for armature voltage, armature current and rated speed.
    5. For the Powerflex 70 AC Drive what are the ratings for Normal Duty Horse Power, Input Amps, Output Amps Continuous, Output Amps for 1 Minute and Output Amps 3 Seconds?
    6. The Allen-bradley Induction Machine is a dual voltage motor depending on how you configure the windings. In the lab it is wired in it’s low voltage configuration. What are the rated voltage and current for motor in the configuration?
    7. For the Allen-bradley Induction Machine what is the rated RPM?
  2. In the lab we use the Fluke 80i-110s current probe with the Fluke 43B. This probe has 2 different settings.
    1. What are these 2 settings and how does each setting effect the measurement current range?
    2. Which setting do we use for the lab?
    3. How do you configure the Fluke 43B to work with this probe?
  3. For the Fluke 43B in INSTRUMENT SETUP on the main menu there are 2 different settings for HARMONICS One being %r and the other being %f. Describe what these 2 settings are and which one we use in the lab?
  4. For the 2 different Variable Speed Drives used in the lab what do you use to control the desired speed?
    1. For the PLX15 DC Drive?
    2. For the Powerflex 70 AC Drive?
  5. The Sprint Electric PLX15 used in the lab is a “4-Quadrant” DC Drive, describe in your own words what this means?
  6. Give the File, Group and Parameter information for the following Parameters on the Powerflex 70 AC Drive.
    1. Output Freq
    2. Output Current
    3. Rated kW
    4. Motor Type
    5. Motor Rated RPM
    6. Torque Pref Mode
    7. Maximum Freq
    8. Run Boost
  7. Give 3 important safety rules to follow while completing this laboratory.

2.3 Safety

3 Experimental Procedure

3.1 Fluke 43B Setup

  1. Take out the Fluke 43B - Power Quality Analyser and plug it in using the supplied power adaptor. The battery on these devices doesn’t last long and is typically dead.
  2. Connect both the voltage probes (available on the wall) with the 4mm test probes and the supplied current probe to channels 1 and 2 respectively.
  3. Instrument setup
    • Configure the probes
      • Turn the Fluke 43B On, hit MENU and go down to INSTRUMENT SETUP, then to PROBES and make sure TEST LEADS is selected for input 1 and 10mV/A is selected for input 2. Press F1 to go BACK.
    • Function preferences
      • In FUNCTION PREFERENCES select %f and DC .. 21 for HARMONICS and the POWER selection doesn’t matter.
  4. Current probe setup
    • Turn the probe on to the same setting that was selected above 10mV/A. A green indicator light should also turn on. If not the battery may need to be replaced, request your LI or TA to do the replacement. There is also a red indicator light on the probe. This light will turn on when the current is above the maximum current the probe can measure (100Apk on this setting).
    • Zero the current probe using the Fluke 43B and the black dial on the current probe labelled ZERO. To do this, from the main menu select VOLTS/AMPS/HERTZ to measure current which is displayed on the bottom half of the screen. With the current probe completely closed and not clamped on a wire adjust the current probes ZERO dial until the current reading on the Fluke 43B is at as close to zero as you can achieve.
  5. Quickly go through the remaining menus on the Fluke 43B to familize yourself with functions that ti can preform. See the Fluke 43B Page for for information.

Warning

Failure to setup your probes and functions properly and not zeroing the current probe can lead to significant errors in your measurements. Remember to periodically check that the battery in the current probe hasn’t died or the current probes ZERO hasn’t drifted during your experiment.

3.2 Resistance (Cold)

  1. Use the Fluke 43B to measure the resistance of both motors when they are cold.
    • From the MENU select OHMS/CONTINUITY/CAPACITANCE and leave it on the RESISTANCE setting. Use the voltage test leads on input 1 to measure the resistances in Table 1 and record your measurements in the appropriate table on the results sheet.

Figure 1: Motor Resistance Measurement Connections

Note

When you measure the resistance of a delta connected machine you are actually making the following measurement. \[R_{XY} = R_A \parallel (R_C + R_B)\]

3.3 DC Drive/Motor Setup

Figure 2: DC Drive and Motor Connections Diagram

  1. Use the shielded safety banana leads (available on the wall) to connect the circuit above.
    1. Plug in the PLX15 DC Drive control power supply available on the right side of the unit to a standard 120V recepticle. (this supply needs to be maintained at all times during drive operation)
    2. Using the appropriate color banana leads, connect the supply terminals A, B, C and GND of the 3 Phase Power Supply to input terminals L1, L2, L3 and GND of the PLX15 DC Drive, respectively.
    3. Using the appropriate color banana leads, connect the armature output terminals *A+** and *A-** of the PLX15 DC Drive to the armature terminals +A1 and -A2 of the Baldor PMDC Machine, respectively. Also make sure you connect the Baldor PMDC Machine to earth ground.

Circuit Check

At this point please get a lab instructor (LI) or teaching assistant (TA) to double check your wiring.

  1. Connect the Fluke 43B at the input of the drive as a 3 phase input connection as shown below.
    • Use the current probe on the red (phase A) wire making sure that the arrow on the probe is pointing from supply to drive.
    • Use the positive red voltage lead of the Fluke 43B to connect to the the black (phase B/L2) terminal and the black negative lead on the blue (phase C/L3) terminal.
    • Turn the Fluke 43B to the VOLTS/AMPS/HERTZ function from the MENU.

Figure 3: Fluke 43B DC Drive Input Measurement

DANGER

Check that the motors are free to rotate and are clear of any wires/leads/fingers or anything else that could potentially touch them. Especially the shaft as this rotates very fast and has a very significant amount of power. The machine can also get fairly hot when they are operating under load.

  1. The PLX15 DC Drive has the following controls.
    1. A 10 turn potentiometer to control the Speed/Voltage Setpoint limit for the armature voltage of the Baldor PMDC Machine. When this control in fully counter-clockwise the speed and voltage are set to zero and when it is fully clockwise the machine speed is set to approximately 1800rpm and the Voltage is set to approximately 180VDC, the Baldor PMDC Machine’s approximate rated speed and voltage.
    2. Another 10 turn potentiometer to control the Torque/Current Setpoint limit for the armature current of the Baldor PMDC Machine. When this control in fully counter-clockwise the current and torque are set to zero and when it is fully clockwise the current is set to approximately 9.6ADC the Baldor PMDC Machines rated current.
    3. A black Start Button for enabling the output of the PLX15 DC Drive.
    4. A red Stop Button for disabling the output of the PLX15 DC Drive.

DC Drive and Fluke 43B Setup Check

At this point please get a lab instructor (LI) or teaching assistant (TA) to double check your DC Drive and Fluke 43B settings.

Figure 4: PLX15 DC Drive Front Panel

  1. Starting the PLX15 DC Drive and the Baldor PMDC Machine
    1. Make sure that both PLX15 DC Drive control potentiometer knobs are at the minimum setting (fully counter-clockwise).
    2. Press Start on the 3 Phase Power Supply. You will hear a contactor engage and the red light on the power supply should come on.
    3. Push the Start button on the PLX15 DC Drive. You should hear another contractor engage, however nothing should be rotating.
    4. Turn the Torque/Current Setpoint knob approximately 2 turns clockwise from zero so the PLX15 DC Drive can supply the Baldor PMDC Machine with a small current when the Speed/Voltage Setpoint is increase above zero in the next step.
    5. Start to turn the Speed/Voltage Setpoint knob clockwise, which now should allow the machine to start turning slowly. Increase this setpoint by continuing to turn the knob clockwise until maximum is reached. The motor should now be spinning at maximum speed (approximately 1800rpm).

3.3.1 Unloaded DC Drive Input

  1. With the PLX15 DC Drive now controlling the Baldor PMDC Machine at maximum speed at unloaded conditions make the measurements in Table 2 with the Fluke 43B using the appropriate function to recording the values in the appropriate table on the results sheet.

3 Phase Power Measurement

When trying to make a 3 phase power measurement it is important that you select the “\(3\varnothing\)” under the POWER Menu.

  1. Once you have completed all of the measurements required for this section simply hit the Stop button on the PLX15 DC Drive and allow the Baldor PMDC Machine to coast to a stop.

3.3.2 Unloaded DC Drive Output

  1. Move the Fluke 43B’s current probe and voltage leads to the output of the PLX15 DC Drive as shown in Figure 5 so the output of the PLX15 DC Drive can be measured.

Figure 5: Fluke 43B DC Drive Output Measurement

Warning

Check that the Machine Shaft is still clear of anything that can interfere with it.

  1. Press the Start button on the PLX15 DC Drive and allow it to ramp up to maximum speed at unloaded conditions once again. Once at maximum speed make the measurements in Table 3 using the following.
    • The Fluke 43B using the appropriate function to recording the values in the appropriate table on the results sheet. The Fluke 43Bs SCOPE function is able to make many automatic measurements by going into SETUP and selecting the required measurement under Reading for either INPUT 1 or INPUT 2. Caution must be used when using automatic measurements as the reading is only accurate if the SCOPE RANGE and SETUP are appropriate for the measurement being made.
    • The shaft speed using the hand held Monarch Pocket-tach and record it on the results sheet.
    • Using the PLX15 DC Drive you can monitor a few of the drives parameters. Use the green buttons on the drive to navigate though the menu struture. All the required measurements can be found in the DIAGNOSTICS menu which is located at the top level.
      • The right key is used to go down into a menu level
      • The left key is used to go back to the previous menu level
      • The up and down keys is to scroll through the various menus
  1. Once you have completed all of the measurements required for this section simply hit the Stop button on the PLX15 DC Drive and allow the Baldor PMDC Machine to coast to a stop. Reduce both the Speed/Voltage Setpoint and Torque/Current Setpoint to zero (fully counter-clockwise). Also turn off the 3 Phase Power Supply, but leave everything connected as is as you will use it later. However, you can disconnect the fluke 43B as required.

3.4 AC Drive/Motor Setup

Warning

Make sure the 3 Phase Power Supply is off.

Figure 6: AC Drive/Motor Block Diagram

  1. Use the shielded safety banana leads (available on the wall) to connect the circuit above.
    1. Using the appropriate color banana leads, connect the second set of supply terminals A, B, C and GND not being used by the PLX15 DC Drive of the 3ph Supply Box to input terminals R, S, T and GND of the Powerflex 70 AC Drive, respectively.
    2. Using the appropriate color banana leads, connect the output terminals U, V and W of the Powerflex 70 AC Drive to the input terminals X, Y and Z of the Allen-bradley Induction Machine, respectively. Also make sure you connect the Allen-bradley Induction Machine to earth ground.

Circuit Check

At this point please get a lab instructor (LI) or teaching assistant (TA) to double check your wiring.

  1. Connect the Fluke 43B at the input of the drive as a 3 phase input connection as shown below.
    • Use the current probe on the red (phase A) wire making sure that the arrow on the probe is pointing from supply to drive.
    • Use the positive red voltage lead of the Fluke 43B to connect to the the black (phase B/L2) terminal and the black negative lead on the blue (phase C/L3) terminal.
    • Turn the Fluke 43B to the VOLTS/AMPS/HERTZ function from the MENU.

Figure 7: Fluke 43B AC Drive Input Measurement

3.4.1 AC Drive Configuration

  1. Starting the Powerflex 70 AC Drive and Allen-bradley Induction Machine
    1. Press the Start button on the 3 Phase Power Supply so the Powerflex 70 AC Drive boots up.
    2. You must program the drive to operate in open loop V/f mode at the appropriate frequencies and voltages listed later. To do this, you have to use the Human Interface Module (HIM) on the front of the drive. To begin enter the start-up menu from the HIM main menu and enter the data below.

3.4.2 Unloaded AC Drive Input

  1. With the Powerflex 70 AC Drive now controlling the Allen-bradley Induction Machine at 60Hz speed at unloaded conditions make the measurements in Table 4 using the Fluke 43B with the appropriate function to recording the values in the appropriate table on the results sheet.
  1. Once you have completed all of the measurements required for this section simply hit the Stop button on the Powerflex 70 AC Drive and allow the Allen-bradley Induction Machine to coast to a stop.

3.4.3 Unloaded AC Drive Output

  1. Move the Fluke 43B’s current probe and voltage leads to the output of the Allen-bradley AC Drive as shown in Figure 8 so the output of the Allen-bradley AC Drive can be measured.

Figure 8: Fluke 43B AC Drive Output Measurement

Warning

Check that the Machine Shaft is still clear of anything that can interfere with it.

  1. Press the Start button on the Allen-bradley AC Drive and allow it to ramp up to 60Hz at unloaded conditions once again. Once at full speed make the measurements in Table 5 using the following.
    • The Fluke 43B using the appropriate function to recording the values in the appropriate table on the results sheet.
    • The shaft speed using the hand held Monarch Pocket-tach and record it on the results sheet.
    • Using the Powerflex 70 AC Drive you can monitor a few of the parameters. All of the required parameters are in the “Monitor” file under “Metering”.
  1. Once you have completed all of the measurements required for this section just leave the AC Drive/Machine running.

3.5 Circulating Power

  1. With the AC Drive/Machine running at 60Hz we are going to use the DC Drive/Machine to load it. The PLX15 DC Drive is a 4-quadrant DC drive meaning that it not only can supply power to the Baldor PMDC Machine but it can also sink power or regenerate power back on to the grid while the Baldor PMDC Machine is acting like a generator. This is known as circulating power due to the power flowing in a circle as follows:
    • The grid supplies power to the AC Drive and induction motor
    • The induction motor supplies power through the shaft to the PMDC machine now acting as a generator
    • The PMDC Generator returns power back to the grid which is controlled by the 4-quadrant regen PLX15 DC Drive
    • The only actual power drawn from the grid will be the losses in the system, where the power circulating can be much higher.

3.5.1 Loaded AC Drive

  1. With the Powerflex 70 AC Drive still running at 60Hz and the Fluke 43B measuring the output current of the AC Drive with the Fluke 43B on VOLTS/AMPS/HERTZ
    1. Make sure that both of the potentiometer knobs for the Speed/Voltage Setpoint and the Torque/Current Setpoint on the PLX15 DC Drive are set to zero or fully counter-clockwise.
    2. Turn on the PLX15 DC Drive by pushing the Start button. Both Drives are now connected to the grid. However, the PLX15 DC Drive is effectively turned off due to the Torque/Current Setpoint being at zero.
    3. While monitoring the Induction Motors RMS current on the Fluke 43B start to increase the Torque/Current Setpoint on the PLX15 DC Drive. This will result in an increased load on the Induction Motor and the Inductions Motors current should start to increase as well. Continue this until the Induction Motors current reaches its Rated Current of 5.8A.
  2. With the Allen-bradley AC Machine now fully loaded make all of the same measurements you made to the unloaded ac motor again and record all of the values in the appropriate table on the results sheet.

Warning

You can move the Fluke 43B’s current probe and voltage leads around while the machines are running however use extreme caution while doing so by keeping the wires as far away from the machines as possible, especially the rotating shaft.

3.5.2 Loading DC Drive

  1. With the Baldor PMDC Generator now fully loading the Allen-bradley Induction Machine make all of the same measurements you made to the input and output of the PLX15 DC Drive when it was unloaded again. Record all of the values in the appropriate table on the results sheet.

3.6 Resistance (Hot)

  1. Use the same procedure from step 6 when you measured the resistance of both motors when they are cold again now that the machines have been running for a significant time and have had enough time to heat up. Record these measurements in your results sheet.

Results Sign-off

Before you start to cleanup, if you are happy that you have completed all of the measurements required for the lab please get a LI or TA to double check results and sign-off on your results sheet.

Cleanup Sign-off

Please put everything back to where it was when you came into the lab.

  • Disconnect your circuit and leave all of the equipment neatly at your station.
  • Put the Fluke 43B back in the case and make sure the Current Probe is turned off.
  • Hang the Hookup Leads back on the wall neatly.
  • Please make sure you bring all your stuff with you.

Once you are finished cleaing up you need to get another sign-off from a LI or TA.

4 Lab Report

The following is what you are expected to hand-in appropriately one week after completion of the lab. Check Canvas for the exact deadline. Please submit everything as a single pdf with everything together in the following order.

  • Use the first page of your result sheet page as your cover page. Make sure your names, student ID’s, CCID’s and lab section are visible in the table above. You need to obtain the signatures below after completing the Laboratory exercises.
  • Include the results sheet that you made all of your measurements on.
  • The answers to the post lab questions below.

4.1 Questions

  1. In an induction machine this size the stator resistance contributes approximately 30% of the total loss at full load. Explain using the before and after measurements of the stator resistance how the machine efficiency is effected by the temperature of the motor.
  2. Calculate the slip speed and slip at no load and full load for the induction machine, show your work.
  3. Draw a block diagram of the loaded circulating power experiment that was completed in the lab showing the connections between the drives, motors and supply. Assuming the induction machine and the dc machine have an equal amount of power loss. Label the diagram appropriately with the following:
    • The power magitudes with an arrow showing the direction of power flow for each connection point.
    • Calculate the losses and efficiency for each device and label it on your diagram.
    • The shaft with the measured speed and calculated torque.
    • For each electrical connection point that you measured label the rms voltage and current.
    • For each ac electrical connection that you measured label the measured displacement power factor and the currents total harmonic distortion.