reciprocating saw dissection: motor description thomas snowdon
TRANSCRIPT
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Reciprocating Saw Dissection:
Motor Description
Thomas Snowdon
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• 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
DC Electrical Principles
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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.
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Motor Construction
Major Components• Frame• Stator Coils• Rotor• Commutator and Brushes
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• 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
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• Commutator connects the coils to the brushes
• Brushes connected to the battery voltage
• Coil polarity changes as the commutator turns
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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
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Advantages and Disadvantages of DC
MotorsAdvantages:• Variable speed control• Portable• Can handle heavy torque loadsDisadvantages• Complex to build and
expensive• Not as reliable as other motors• Difficulty keeping a constant
speed
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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/
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References
• Fitzgerald, A. E., Charles Kingsley, and Alexander Kusko. Electric Machinery. 3rd ed. McGraw-Hill Book Company, 1971.
• http://www.ni.com/