Specifications

CT Corsair Final Report May 2, 2014
9
Criteria
Servo
Advantages
Servo
Disadvantages
Induction
Advantages
Induction
Disadvantages
Motor
Encoder
 Encoder integrated
 Accurate position
control
 Program required
for gearbox ratio
correction
 Program required
for gearbox ratio
correction
 Encoder separate
 Not accurate
Size
 Less weight
 Smaller
 Similar in size to
original motors
 Heavy
 Up to 50% larger
Price
 Approx.
$6000/motor
 Expensive: high
quality materials &
internal feedback
 Approx.
$3300/motor
 Less expensive
due to external
encoder
Efficiency
 90% efficient
 Magnet rotors lose
less power
between stator and
rotor
 60%-70% efficient
 High power loss
due to motor
materials
Heat Waste
 Low operating
temperature
 Low heat
production
 High operating
temperature
 High heat
production
Operating
Current
 Low current draw
 No magnetizing
current required,
rotor is a
permanent magnet
 High current draw
 Magnetizing
current to make
magnetic field for
rotation
Prototyping
 Hobby servo
motors cheap to
prototype
 Development
libraries available
 Difficult to
prototype: small
induction motors
not readily
available
Drives
Software
 Manufacturer
software included
 Reduced
programming
complexity
 Some drives don’t
come with
manufacturer
software
Controllers
 Microcontrollers
may be an option
depending on
brand
 Drives require
controller; hard to
code
 Price greater than
microprocessor
 Microprocessors
can be used with
VFDs; easy to
code
 Cheaper than
controllers
Price
 Expensive
 VFDs are less
expensive
Compatibility
 Motor/drive must
come from same
manufacturer
 Any VFD works
with any motor
Control
 Positional control
is easy using servo
drives due to built-
in encoder
 Speed control is
easy using VFDs.
Speed proportional
to input frequency
 Complicated
position control
Table 1. Pros and Cons of Induction and Servo Motors and Drives