PASCO SE-8658A User Manual
Includes
Teacher's Notes
and
Typical
Experiment Results
PERMANENT MAGNET
Instruction Manual and
Experiment Guide for the
PASCO scientific
Model SE-8658A
MOTOR
012-07210A
8/99
© 1999 PASCO scientific $5.00
better
10101 Foothills Blvd. • P.O. Box 619011 • Roseville, CA 95678-9011 USA
Phone (916) 786-3800 • FAX (916) 786-8905 • email: techsupp@PASCO.com
ways to
teach science
The exclamation point within an equilateral
triangle is intended to alert the user of
important operating and safety instructions
that will help prevent damage to the
equipment or injury to the user.
012-07210 A Permanent Magnet Motor
Table of Contents
Section ...................................................................................................... Page
Copyright and Warranty, Equipment Return ................................................. ii
Introduction .....................................................................................................1
Equipment ....................................................................................................... 1
Table 1. Equipment Options for Experiments 1 – 3 ....................................... 2
Operation .........................................................................................................3
Assembly—Permanent Magnet Motor ........................................................... 4
Suggested Uses ................................................................................................5
Experiment 1: Operation of the DC Motor ....................................................7
Experiment 2: Operation of AC and DC Generators ................................... 13
Experiment 3: Operation of an AC Synchronous Motor ............................. 19
Teacher’s Guide ............................................................................................ 25
Technical Support ........................................................................... back cover
®
i
Permanent Magnet Motor 012-07210A
Copyright, Warranty, and Equipment Return
Please—Feel free to duplicate this manual
subject to the copyright restrictions below.
Copyright Notice
The PASCO scientific Permanent Magnet Motor
manual (012-07210A) is copyrighted and all rights
reserved. However, permission is granted to non-profit
educational institutions for reproduction of any part of
the manual providing the reproductions are used only
for their laboratories and are not sold for profit.
Reproduction under any other circumstances without
the written consent of copyright holders is prohibited.
Limited Warranty
PASCO scientific warrants the product to be free from
defects in materials and workmanship for a period of
one year from the date of shipment to the customer.
PASCO will repair or replace at its option any part of
the product which is deemed to be defective in material
or workmanship. The warranty does not cover damage
to the product caused by abuse or improper use.
Determination of whether a product failure is the result
of a manufacturing defect or improper use by the
customer shall be made solely by PASCO scientific.
Responsibility for the return of equipment for warranty
repair belongs to the customer. Equipment must be
properly packed to prevent damage and shipped
postage or freight prepaid. (Damage caused by
improper packing of the equipment for return shipment
will not be covered by the warranty.) Shipping costs
for returning the equipment after repair will be paid by
PASCO scientific.
Equipment Return
Should the product have to be returned to PASCO
scientific for any reason, notify PASCO scientific by
letter, phone, or fax BEFORE returning the product.
Upon notification, the return authorization and
shipping instructions will be promptly issued.
NOTE: NO EQUIPMENT WILL BE
ACCEPTED FOR RETURN WITHOUT AN
AUTHORIZATION FROM PASCO.
When returning equipment for repair, the units must be
packed properly. Carriers will not accept responsibility
for damage caused by improper packing. To be certain
the unit will not be damaged in shipment, observe the
following rules:
1. The packing carton must be strong enough for the
item shipped.
2. Make certain there are at least two inches of
packing material between any point on the apparatus
and the inside walls of the carton.
3. Make certain that the packing material cannot shift
in the box or become compressed, allowing the
instrument come in contact with the packing carton.
Address: PASCO scientific
10101 Foothills Blvd.
P.O. Box 619011
Roseville, CA 95678-9011
Credits
Author: Jim Housley
Editor: Sunny Bishop
Phone: (916) 786-3800
FAX: (916) 786-3292
email: techsupp@pasco.com
web: www.pasco.com
ii
®
012-07210A Permanent Magnet Motor
Introduction
The PASCO SE-8658A Permanent Magnet Motor
operates on AC or DC current, and it can be used to
generate alternating or direct current.
Students can not only explore properties of AC and DC
generators with this apparatus, they can also discover
Equipment
The Permanent Magnet Motor includes
- armature with split ring commutator at one end
and a dual slip-ring commutator at the other
- field magnet, shaft and brush assembly
- maintenance items
- manual
- ceramic magnet
key concepts and relationships concerning motors and
electric current, using the Permanent Magnet Motor in
conjunction with an AC or DC power supply and
sensors for voltage, current, and rotational speed.
retaining nut
dual slip-ring
commutator
split ring
commutator
shaft
N
field
magnets
ceramic
magnet
armature
Safety precautions
brushes
shaft and
field
magnet
assembly
- Always wear safety goggles when in a room where the Permanent Magnet Motor is being used.
- Keep fingers and other objects away from the spinning armature.
- Choose power sources that limit current to not more than one ampere (1.0 A). The motor may overheat if
this current is exceeded or if power is applied continuously, especially if the armature is not rotating. The
motor is intended only for intermittent operation.
- Disconnect any power source whenever the motor is to be left unattended.
1
Permanent Magnet Motor 012-07210A
➤ NOTE: Although the instructions for experiments in this manual are for mechanical setups with
specific PASCO equipment, the experiments in this manual may be set up in a variety of ways,
depending upon the equipment you have available. They can all be done with or without the PASCO
Science
Workshop computer interface. Table 1 lists the equipment suggested for optional experimental
setups. You may be able to substitute other equipment for the PASCO models listed in this table.
Table 1. Equipment Options for Experiments 1– 3
Experiment:
Experiment 1: DC Motor
no computer interface x x x
no computer interface x x x or x
computer interface x x x x x x
computer interface x x x or x
Experiment 2: AC/DC Generator
no computer interface x x x
computer interface x x x x or x
Experiment 3: Synchronous AC Motor
no computer interface x x x x or x
computer interface x x x x x x
Equipment:
Permanent Magnet Motor (SE-8658A)
Variable Gap Magnet (EM-8641)
Low Voltage DC Power Supply (SE-9712, 9720, or equiv.*)
Low Voltage AC/DC Power Supply (SF-9584A)
Power Amplifier (CI-6552A)
Digital Function Generator (PI-9587C)
Multimeter (SB-9623) or Ammeter (SF-9569)
Galvanometer (SF-9500) or Multimeter (SB-9623)
Voltage Sensor (CI-6503)
Science Workshop Interface (300 or 500)
Science Workshop Interface (700 or 750)
Digital Photogate Timer (SF-9215A)
Digital Stroboscope (SF-9211)
computer interface x x x x or x x
* If your power supply does not have the capability to quantify output current, you can
measure it using an ammeter. Be sure to limit the current to 1 A max. to avoid damaging
the equipment. The value can also be calculated from the voltage drop across a small value
series resistor. This option prevents damage to a potentially sensitive ammeter.
2
012-07210A Permanent Magnet Motor
Operation
Options for electrical connections
• Banana-style plugs may be inserted into openings in
the base of the motor.
• Large alligator clips may be attached to the brass
posts that hold the brushes.
• Small alligator clips may be attached directly to the
ends of the brushes where they protrude from the
slits in the brass posts.
Power Sources Warnings
It is important to limit the current of the
power source to 1.0 A to avoid damaging
the coils of the armature. This may be
done by:
• Choosing a power supply that may be
set to limit the current to a maximum
value of 1.0 (See Table 1 for specific
suggestions for power sources);
• Using a PASCO CI-6552A Power
Amplifier, which automatically limits
current to 1.0 A;
• Carefully monitoring current with:
- The power supply’s built-in current
meter, or
- Science Workshop and the CI-6556
Current Sensor, or
- A voltmeter or multimeter, by
measuring the voltage drop across a
low-value series resistor (such as 0.51
ohm, 1 watt), and calculating the
current.
For power supplies that do not have the
capability to measure output voltage, use
a multimeter or voltmeter to insure that
the current does not exceed 1.0 A. (See
Table 1 for specific suggestions for power
sources.)
Starting the motor
• The motor is not self-starting. Immediately after
you apply the power, start the motor manually by
grasping the black plastic bushing at the top of the
armature assembly between your thumb and
forefinger and spinning the armature.
• With the Permanent Magnet Motor configured as
either a DC or universal motor, almost any
attempt you make at spinning the armature will
result in successfully starting the motor; only the
direction of the spin is important.
• When configured in an AC synchronous mode,
the motor must be spun at a speed that
approximately matches the frequency of the
power source. This is impractical at frequencies
much above 30 Hz, and some students may
require assistance even a lower frequencies.
Maintenance and Storage
• The motor may be stored in the plastic bag
furnished; this will keep it dust free and reduce
problems of corrosion that may occur in areas
having high humidity.
• The commutators and brushes will experience
wear, oxidation, and pitting and will require
attention from time to time. Rotate the armature
slowly by hand and monitor current flow or
sense the force developed to determine whether
proper contact is occurring between brushes and
commutator. To restore proper operation, clean
the contacts with emery paper or shift the
brushes somewhat to expose new surfaces.
• Careless installation of the armature onto the
shaft might bend the brushes. You can easily
bend them back into their original shape with
finger pressure.
➤ NOTE: If you are using a PASCO
CI-6502A Power Amplifier with a
CI-6500 Interface System, the distorted
waveform light will turn on during
operation of the motor, but no damage is
being done to the Power Amplifier; you
can ignore the light.
3
Permanent Magnet Motor 012-07210A
Initial Assembly
Initial Assembly of Permanent Magnet
Motor
1. Locate the part shown in the diagram below.
retaining nut
dual slip-ring
commutator
(this end down for
AC motor)
split ring
armature
field
magnets
commutator
(this end down
for DC motor)
shaft
2. Gently lower the armature onto the shaft. To make
a DC motor, the split ring commutator should be
down; for an AC motor, the dual slip-ring
commutator should be down. Carefully rotate the
armature back and forth to separate the brushes and
allow the commutator to slip down between them.
If necessary, insert a pencil or similar object down
between the brushes. Use only the most delicate
force to avoid bending the brushes and necessitating
adjustments or repairs. Screw retaining nut onto
shaft.
3. Refer to the instructions included in experiments 1–
3 for details of the electrical connections.
➤ The motor may be left assembled for storage.
brushes
Figure 1
Permanent Magnet Motor Assembly
4
012-07210A Permanent Magnet Motor
Suggested Uses
Operation as a DC motor
The Permanent Magnet Motor can be used to
demonstrate the operation of a DC motor ( Experiment
1). Students can explore relationships between motor
speed and voltage, as well as between direction of
armature rotation and polarity, learning key concepts
including: action of the split ring commutator,
dependence of speed on voltage, dependence of
direction of rotation on polarity, right-hand rule, and
direction of current flow from positive to negative.
Action of AC and DC generators
Spinning the armature by hand while it is connected to
a sensitive DC meter or to the Signal Interface II shows
the action of an AC generator, as well as the rectifying
action of the commutator in a DC generator
(Experiment 2).
Operation of a synchronous AC motor
Coupled with an AC signal supplied by the PASCO
PI-9587C Digital Function Generator/Amplifier,
Science Workshop 700 or 750 Interface and CI-6552A
Power Amplifier, or a similar function generator, the
Permanent Magnet Motor will operate in sync with 15
to 30 Hz (and often wider range) signals (Experiment
3). Students can explore the relationship between AC
voltage and motor speed, as well as between AC
current frequency and motor speed. They can conduct
detailed explorations of the precision of synchronism
of AC current and motor speed with a PASCO SF-9211
Digital Stroboscope or PASCO ME-9215A Digital
Photogate Timer with memory or by observing the
stroboscopic effect of an ordinary fluorescent lamp at
selected motor speeds. As a result, they learn key
concepts, including the independence of AC motor
speed and voltage, dependence of AC motor speed on
current frequency, and action of a dual slip-ring
commutator.
Additional possibilities
The Permanent Magnet Motor can be used to
determine the speeds of maximum power and
maximum efficiency of a DC motor by varying the load
while simultaneously measuring the speed, torque, and
armature current. In this experiment, you can measure
the motor’s speed with a photogate or stroboscope.
5
Permanent Magnet Motor 012-07210A
6
012-07210A Permanent Magnet Motor
Experiment 1: Operation of the DC Motor
EQUIPMENT NEEDED:
•Permanent Magnet Motor
• low voltage DC power supply, limited to 1 A • patch cords
• multimeter • small piece of masking tape
Purpose
The purpose of this experiment is to demonstrate the operation of the DC motor in terms of basic
concepts of electromagnetism.
Theory
The field magnets are permanent magnets possessing a north pole and a south pole that interact
with the north and south poles of the armature (an electromagnet when connected to an electric
current). Like poles repel, while unlike poles attract. The armature rotates until its north pole is
as close as possible to the south pole of the permanent magnet (and also as far as possible from
the north pole). Inertia carries the armature past this point. However, as the armature passes this
point, the commutator reverses the direction in the coils, so that the poles of the coils are suddenly
repelled by the nearby field magnets. Thus another half-turn occurs, and this process occurs again
and again.
Setup
A better explanation involves an understanding of fields.
The field magnets produce a magnetic field that passes
through the gap between the pole pieces. When current
passes through the turns of the armature in the presence
of the field, forces act to cause a torque that rotates the
armature. Inertia carries the armature past the position
of no torque to the point where the torque would force
the armature back in the other direction. However, at that
point the commutator reverses the direction of current in
the armature so the torque continues to act in the original
direction.
1. Gently lower the armature onto the shaft with the
split ring commutator down (Figure 1.1). Carefully
rotate the armature back and forth to separate the
brushes and allow the commutator to slip down
between them. If necessary, insert a pencil or similar
object down between the brushes. Use only the most
delicate force to avoid bending the brushes and
necessitating adjustments or repairs.
2. Connect the motor to the power source by one of
these methods ( Figure 1.2):
• Insert banana plugs into the openings in the
ends of the plastic brush older; or
retaining nut
dual slip-ring
commutator
armature
field
magnets
brushes
Figure 1.1
Assembly of the Permanent Magnet Motor
split ring
commutator
shaft
7
Loading...