Rockwell Automation 150 MNL/SMC DIALOG+/APP-PROD GUIDE - Manual (Page 189)

Glossary-2
• Dynamic Braking (DC Drives) – Slows the motor by applying a resistive load
across the armature leads after disconnection from the DC supply. This must
be done while the motor field is energized. The motor then acts as a generator
until the energy of the rotating armature is dissipated. This is not a holding
brake.
• Motor Mounted or Separately Mounted Brake is a positive action,
mechanical, friction device. Normal configuration is such that when the power
is removed, the brake is set. This can be used as a holding brake. (Note: A
Separately Mounted Brake is not one which is located on some part of the
mechanical drive train other than the motor.)
• Regenerative Braking is similar to Dynamic Braking, but is accomplished
electrically. The generated power is returned to the line through the powe
converter. It may also be dissipated as losses in the converter (within its
limitations).
• SMB

Smart Motor Braking – An Allen-Bradley smart motor braking
feature of an SMC

smart motor controller.
Breakaway Torque The torque required to start a machine from standstill. Breakaway torque is always
greater than the torque needed to maintain motion.
Breakdown Torque The breakdown torque of an AC motor is the maximum torque that the motor will
develop with rated voltage applied at rated frequency.
Buffer 1. In software terms, a register or group of registers used for temporary storage of
data to compensate for transmission rate differences between the transmitter
and receiving device.
2. In hardware terms, an isolating circuit used to avoid the reaction of one circuit
with another.
C.E.M.F. Abbreviation for counter electromotive force, which is the product of a motor
armature rotating in a magnetic field. This generating action takes place wheneve
a motor is rotating. Under stable motoring conditions, the generated voltag
(C.E.M.F.) is equal to the voltage supplied to the motor minus small losses.
However, the polarity of the C.E.M.F. is opposite to that of the power being
supplied to the armature.
Closed Loop Closed loop refers to a regulator circuit in which the actual value of the controlled
variable (e.g., speed) is sensed and a signal proportional to this value (feedback
signal) is compared with a signal proportional to the desired value (reference
signal). The difference between these signals (error signal) causes the actual valu
to change in the direction that will reduce the difference in signals to zero.
Cogging A condition in which a motor does not rotate smoothly but “steps” or “jerks” from
one position to another during shaft revolution. Cogging is most pronounced at
low motor speeds and can cause objectionable vibrations in the driven machine.