Download Reciprocating Saw Dissection: Motor Description

Reciprocating Saw
Dissection:
Motor Description
Thomas Snowdon
DC Electrical Principles
• When power is from a battery
the current is called DC for
direct current
• Motors that operate from
battery power are called DC
motors
• Current flow from a battery is
always in the same direction
• Current magnitude in a coil is
dependant on battery voltage
and wire resistance
Design Principles
• Driven by electromagnetics
• Like magnetic poles repel, opposite
magnetic poles attract
• Current passed through a coil of
wire produces a magnetic field
• Changing the direction of current in
a coil reverses the magnetic field
• The amount of current in a coil will
determine the strength of the poles
or magnetic field.
Motor Construction
Major Components
• Frame
• Stator Coils
• Rotor
• Commutator and Brushes
• Frame is made of metal and
supports the other parts
• Stator can be made of either
permanent magnets or coils of
wire on a steel core
• Rotor is made up of a shaft, a
set of wire coils, and the
commutator
• Rotor shaft is supported by
bearings in the frame
• Shaft extends out of the motor
to drive tool
• Commutator connects the coils to the
brushes
• Brushes connected to the battery
voltage
• Coil polarity changes as the
commutator turns
Operation
• Motor creates a rotating motion
from the battery power
• As the motor rotor turns the
commutator switches the
current flow in the rotor coils
• Motor shaft has a gear
attached to drive the next piece
of the tool
• Speed of the motor is
dependant on the current flow
through the coils
Advantages and
Disadvantages of DC
Motors
Advantages:
• Variable speed control
• Portable
• Can handle heavy torque loads
Disadvantages
• Complex to build and
expensive
• Not as reliable as other motors
• Difficulty keeping a constant
speed
Conclusion
• The motor used in this tool is a
DC type motor
• Operates on battery power
• Runs at variable speeds
• Can handle heavy torque loads
created by tool use
References
• Fitzgerald, A. E., Charles Kingsley, and
Alexander Kusko. Electric Machinery. 3rd
ed. McGraw-Hill Book Company, 1971.
• http://www.ni.com/
References
• Fitzgerald, A. E., Charles
Kingsley, and Alexander
Kusko. Electric Machinery. 3rd
ed. McGraw-Hill Book
Company, 1971.
• http://www.ni.com/