Rockwell Automation MinPak Plus DC Drive User Manual - Manual (Page 67)

B:1
B: GLOSSARY OF TERMS
Altitude: The atmospheric altitude (height above sea level) at which the motor or controller will be
operating.
Armature: The portion of the DĆC motor which rotates.
RatedFull LoadCurrent: Armature current in amperes.
Armature Resistance:
Measured in ohms at 25 degrees Celsius (cold).
Base Speed: The speedwhich a DĆC motor develops at ratedarmature andfieldvoltage with ratedload
applied.
Chassis Ground: Any electrical connection to the metal body of the controller.
Constant Speed: Motor which changes speedonly slightly from a noĆloadto a fullĆloadcondition.
Direct Current: A current that flows only in one direction in an electrical circuit. It may be continuous or
discontinuous and it may be constant or varying.
DĆC Motor: A motor using either generatedor rectifiedDĆC power. A DĆC motor is usually usedwhen
variable speedoperation is required.
Earth Ground: The central groundfor all electrical andAĆC power within a facility. It may be the plant,
magnetics, equipment, electrical, circuit, neutral or reference ground, depending on the
nomenclature usedat a facility.
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 fieldwith 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 expressedas a function
of torque andRPM. For motors, the following approximate formula may be used:
HP = T x RPM / 5250;where HP = horsepower,
T = Torque (in lb. ft.), and
RPM = revolutions per minute.
Identification: • Frame designation (actual frame size in which the motor is built)
• Horsepower, speed, design and enclosure
• Voltage, frequency andnumber of phases of power supply
• Class of insulation andtime rating
• 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(storedkinetic energy). If this continuedrotation 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
measuredin 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..