Rockwell Automation FlexPak Plus DC Drive - Manual (Page 64)

B:1
B: GLOSSARY OF TERMS
Altitude: The atmospheric altitude (height above sea level) at which the motor or controller will be
operating.
Armature: Theportion of theDĆC motor which rotates.
Rated Full Load Current: Armature current in amperes.
Armature Resistance:
Measured in ohms at 25 degrees Celsius (cold).
Base Speed: The speed which a DĆC motor develops at rated armature and field voltage with rated load
applied.
Constant Speed: Motor which changes speed only slightly from a noĆload to a fullĆload condition.
Direct Current: A current that flows only in one direction in an electrical circuit. It may be continuous or
discontinuous and it may beconstant or varying.
DĆC Motor: A motor using either generated or rectified DĆC power. A DĆC motor is usually used when
variable speed operation is required.
Efficiency: The ratio of mechanical output to electrical input. It represents the effectiveness with which
the motor converts electrical energy to mechanical energy.
Electrical Time Constant: The ratio of electrical inductance to armature resistance. Electrical time constant in
seconds defined as electrical:
T/C = La x Ia / Hot IR voltage drop
Field: A term commonly used to describe the stationary (stator) member. The field provides the
magnetic field with which the mechanically rotating (armature or rotor) member interacts.
Horse Power: The measure of the rate of work. One horsepower is equivalent to lifting 33,000 pounds to
a height of one foot in one minute. The horsepower of a motor is expressed as a function
of torqueand RPM. For motors, thefollowing approximateformula may beused:
HP = T x RPM / 5250;where HP = horsepower,
T = Torque (in lb. ft.), and
RPM = revolutions per minute.
Identification: • Framedesignation (actual framesizein which themotor is built)
• Horsepower, speed, design and enclosure
• Voltage, frequency and number of phases of power supply
• Class of insulation and timerating
• Application
Inertial Load: A load (flywheel, fan, etc.) which tends to cause the motor shaft to continue to rotate after
the power has been removed (stored kinetic energy). If this continued rotation cannot be
tolerated, some mechanical or electrical braking means must be applied. This application
may require a special motor due to the energy required to accelerate the inertia. Inertia is
measured in either lb. ft. or oz. in. squared.
Inertia reflected to the shaft of the motor = (load RPM)^2/Motor RPM
Motor: A device that converts electrical energy to mechanical energy to turn a shaft.
Nameplate: The plate on the outside of a motor which describes the motor, HP, voltage, RPM, efficiency,
design, enclosure, etc..
RPM: Revolutions per Minute Ć The number of times per minute the shaft of the motor (machine)
rotates.