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.
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.
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.
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.
Pre-lab
Questions
- Equipment Ratings.
- What is the voltage and current rating of the 3 Phase Power
Supply in the lab?
- For the PLX15 DC Drive what are the Rated Output Power in
kW at 460V?
- For the PLX15 DC Drive what is the Maximum Continuous
Current in amps for both the input AC and output DC?
- for the Baldor PMDC Machine what are the Name Plate ratings
for armature voltage, armature current and rated speed.
- 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?
- 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?
- For the Allen-bradley Induction Machine what is the rated
RPM?
- In the lab we use the Fluke 80i-110s current probe with the
Fluke 43B. This probe has 2 different settings.
- What are these 2 settings and how does each setting effect the
measurement current range?
- Which setting do we use for the lab?
- How do you configure the Fluke 43B to work with this
probe?
- 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?
- For the 2 different Variable Speed Drives used in the lab what do
you use to control the desired speed?
- For the PLX15 DC Drive?
- For the Powerflex 70 AC Drive?
- The Sprint Electric PLX15 used in the lab is a “4-Quadrant”
DC Drive, describe in your own words what this means?
- Give the File, Group and Parameter information for the following
Parameters on the Powerflex 70 AC Drive.
- Output Freq
- Output Current
- Rated kW
- Motor Type
- Motor Rated RPM
- Torque Pref Mode
- Maximum Freq
- Run Boost
- Give 3 important safety rules to follow while completing this
laboratory.
Safety
Experimental
Procedure
Fluke 43B Setup
- 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.
- 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.
- 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.
- 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.
- 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.
Resistance
(Cold)
- 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.
Note
When you measure the resistance of a delta connected machine you are
actually making the following measurement. \[R_{XY} = R_A \parallel (R_C + R_B)\]
DC Drive/Motor
Setup
- Use the shielded safety banana leads (available on the wall) to
connect the circuit above.
- 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)
- 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.
- 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.
- 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.
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.
- The PLX15 DC Drive has the following controls.
- 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.
- 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.
- A black Start Button for enabling the output of the
PLX15 DC Drive.
- 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.
- Starting the PLX15 DC Drive and the Baldor PMDC
Machine
- Make sure that both PLX15 DC Drive control potentiometer
knobs are at the minimum setting (fully counter-clockwise).
- 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.
- Push the Start button on the PLX15 DC Drive. You
should hear another contractor engage, however nothing should be
rotating.
- 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.
- 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).
Unloaded DC Drive
Output
- 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.
Warning
Check that the Machine Shaft is still clear of anything that can
interfere with it.
- 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
- 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.
AC Drive/Motor
Setup
Warning
Make sure the 3 Phase Power Supply is off.
- Use the shielded safety banana leads (available on the wall) to
connect the circuit above.
- 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.
- 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.
- 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.
AC Drive
Configuration
- Starting the Powerflex 70 AC Drive and Allen-bradley
Induction Machine
- Press the Start button on the 3 Phase Power Supply
so the Powerflex 70 AC Drive boots up.
- 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.
Main Menu:
Start-Up
Note
You won’t be able to run the motor to do the Motor Test section
without first going to step 6 to disable the digital inputs so you don’t
get a (Start Inhibit) error. So after step 2, first go to step 6 and
then return to do the direction test in step 3.
- Input Voltage
- 208V 60Hz
- Reset the parameters to default
- Motor data/ramp
- PWR Units = HP
- NP Power = 2.00
- NP FLA (full load amp) = 5.8
- NP Volt = 230V (Can only put in a maximum of 208V)
- NP Hertz = 60
- NP RPM = 1730
- Stop Mode = Coast
- DC Resistor type = Internal
- Accel time = 10 Sec
- Decel time = 10 Sec
- S-curve = 0%
- Motor Test
- Direction test
- Hold Jog button to identify the motor direction.
- Do a static tune
- Speed Limits
- Prohibit reverse operation
- Maximum speed = 60
- Minimum speed = 0
- Speed Control
- Speed control = Local HIM port 1
- Start/Stop/IO input
- Digital Inputs – Custom Configuration = Digital Input (1-6) = 0 “Not
used”
- Done
Quick Access to Parameters
You can use the menus to navigate to a parameter, however if you
don’t know which menu to find the parameter in it can be quicker to just
press ALT and then PARAM# on the HIM and then
punch in the known parameter number.
- Other Powerflex 70 AC Drive parameters that you need to
modify.
- 53 - Torque Perf Mode set to 2 “Custom V/Hz”
- 69 - Start/Acc Boost set to “0”
- 70 - Run Boost set to “0”
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.
AC Drive and Fluke 43B Setup Check
At this point please get a lab instructor (LI) or teaching assistant
(TA) to double check your AC Drive and Fluke 43B settings.
- Your drive should now be ready to operate, with a green indicator
light on the front. (Not red or yellow flashing). To operate the drive
from the main menu, press escape, this should give you the 3 meter
display. From this display you can control the command frequency by
either using the keypad to enter in a frequency or use the arrow keys to
slowly increase or decrease the command frequency. Use the red and green
buttons on the Keypad to start and stop the drive. Enter a desired
frequency of 20Hz and the motor should accelerate to that speed. If
everything seems to be okay enter in a desired frequency of 60Hz and
allow the motor to accelerate.
Unloaded AC Drive
Output
- 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.
Warning
Check that the Machine Shaft is still clear of anything that can
interfere with it.
- 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”.
- Once you have completed all of the measurements required for this
section just leave the AC Drive/Machine running.
Circulating
Power
- 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.
Loaded AC
Drive
- 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
- 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.
- 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.
- 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.
- 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.
Loading DC
Drive
- 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.
Resistance (Hot)
- 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.
Lab Report
The following is what you are expected to hand-in one week (by
4:00pm) after completion of the lab. You only have to hand-in one copy
per group. There is an assignment box in the ETLC atrium marked
ECE432 Lab: H11, H31, H41. Please, staple 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.
Questions
- 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.
- Calculate the slip speed and slip at no load and full load for the
induction machine, show your work.
- 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.