- General Electric Computer Accessories User Manual

GEH-6385 Reference and Troubleshooting, 2300 V Drives Chapter 3 Paramters/Functions •
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• 3-113
Flux decay waiting: When a V/Hz or Torque regulated
Tachless drive is stopped and the motor is de-energized there
is a requirement to wait for the motor flux to decay before
restarting (1 to 20 seconds, depending on motor rotor circuit
time constant). If a restart is attempted before the flux decays
to a low enough level (2% of rated), the drive will be blocked
from a restart and a Run cmd w high flux alarm will occur.
Restarting drive at zero speed: When a V/Hz or Torque
regulated Tachless drive is restarted at zero speed any motion
produced externally during its pre-flux sequence (motor
electrical time constant dependent, typical 0.5 to 2 sec.) will
lead to malfunction. If the motor was stationary when
restarted a sufficient delay coordinating other drives or
machinery that prevents start of any motion must be
guaranteed until after the pre-flux sequence is complete and
the drive is ready to produce torque.
Operation at zero speed: If there is a need for the Tachless
drive (Torque regulated or V/Hz with Auto-boost) to sit at
zero speed either the Enb adaptv full flx (see Sequencer
Commands)must be used or the drive must be stopped and
turned off then restarted when it is desired to move.
Prolonged zero speed operation without the aforementioned
precaution will cause drive malfunction.
Operation with Regenerative load: If there is a need for
regenerative load operation (Torque regulated or V/Hz with
Auto-Boost) near zero speed, the minimum operating speed
must be higher than the maximum anticipated slip rpm of the
motor. This is required to avoid zero frequency operation
(failure mode for Vector Tachless drive).
Functional use
• Speed Feedback Calculation
• Tach Loss Detection
Motor efficiency
Parameter Motor efficiency specifies the motor efficiency, the mechanical output
power that can be obtained at nameplate conditions, expressed as a percentage of the
electrical power input. The efficiency is normally specified on the motor nameplate.
Typical motor efficiencies are near 93%. High-efficiency motors may have
efficiencies in excess of 95%.
Units
• Presentation units: Percent
• Internal control units: Per unit