User Manual Instruction Manual

Application Notes 13-85
The Overspeed Limit is added to Maximum Speed and the sum of the two (Speed
Limit) limits is output. This sum (Speed Limit) is compared to Maximum Frequency
and an alarm is initiated which prevents operation if the Speed Limit exceeds
Maximum Frequency.
13.34 Power Loss
Some processes or applications cannot tolerate drive output interruptions caused by
momentary power outages. When AC input line power is interrupted to the drive, user
programming can determine the drive’s reaction.
13.34.1 Terms
The following is a definition of terms. Some of these values are drive parameters and
some are not. The description of how these operate is explained below.
Figure 13.28 – Typical V/Hz Curve for Full Custom (with Speed/Frequency Limits)
Frequency
Overspeed
Limit
(83)
Frequency Trim
due to Speed
Control Mode
Max Volts
(54)
Motor Volts
(41)
Run
Boost
(70)
Break Volts
(71)
Start Boost
(69)
Allowable Output Frequency Range - Normal Operation
Allowable Speed Reference Range
Allowable Output Frequency Range -
Bus Regulation or Current Limit
Maximum
Freq
(55)
Motor NP Hz
(43)
0 Break
Frequency
(72)
Max
Speed
(82)
Min
Speed
(81)
Output
Freq Limit
V
o
l
t
a
g
e
Term Definition
Vbus The instantaneous DC bus voltage.
Vmem The average DC bus voltage. A measure of the “nominal” bus
voltage determined by heavily filtering bus voltage. Just after the
pre-charge relay is closed during the initial power-up bus pre-charge,
bus memory is set equal to bus voltage. Thereafter it is updated by
ramping at a very slow rate toward Vbus. The filtered value ramps at
2.4V DC per minute (for a 480VAC drive). An increase in Vmem is
blocked during deceleration to prevent a false high value due to the
bus being pumped up by regeneration. Any change to Vmem is
blocked during inertia ride through.
Vslew The rate of change of Vmem in volts per minute.
Vrecover The threshold for recovery from power loss.