Reciprocating Saw Dissection: Motor Description Thomas Snowdon

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

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,

References Fitzgerald, A. E., Charles Kingsley, and Alexander Kusko. Electric Machinery. 3rd ed. McGraw-Hill Book Company,