Rockwell Automation Publication 520-QS001A-EN-E - March 2014 23
PowerFlex 520-Series Adjustable Frequency AC Drive
A438 [DB Threshold] 10.0/110.0% 0.1% 100.0%
Sets the DC bus voltage threshold for Dynamic Brake operation. If DC bus voltage rises above this level,
Dynamic Brake turns on. Lower values makes the dynamic braking function more responsive but may
result in nuisance Dynamic Brake activation.
ATTENTION: Equipment damage may result if this parameter is set to a value that causes the dynamic
braking resistor to dissipate excessive power. Parameter settings less than 100% should be carefully
evaluated to ensure that the Dynamic Brake resistor's wattage rating is not exceeded. In general, values
less than 90% are not needed. This parameter's setting is especially important if parameter A437 [DB
Resistor Sel] is set to 2 “NoProtection”.
A439 [S Curve %] 0/100% 1% 0%
Enables a fixed shape S-Curve that is applied to the acceleration and deceleration ramps (including jog).
S-Curve Time = (Accel or Decel Time) x (S-Curve Setting in percentage)
A440 [PWM Frequency] 2.0/16.0 kHz 0.1 kHz 4.0 kHz
Sets the carrier frequency for the PWM output waveform. The chart below provides derating guidelines
based on the PWM frequency setting.
Important: Ignoring derating guidelines can cause reduced drive performance. The drive may
automatically reduce the PWM carrier frequency at low output speeds, unless prevented from doing so by
A540 [Var PWM Disable].
A441 [Droop Hertz@ FLA] 0.0/10.0 Hz 0.1 Hz 0.0 Hz
Reduces the frequency based on current. This frequency is subtracted from the commanded output
frequency. Generally Slip and Droop would not both be used, but if both are enabled they simply subtract
from each other. Typically used in load sharing schemes.
A442,
A444,
A446
[Accel Time x] 0.01 s 0.00/600.00 s 10.00 s
Time for the drive to ramp from 0.0 Hz to P044 [Maximum Freq] if Accel Time x is selected.
Accel Rate = [Maximum Freq] / [Accel Time]
A443,
A445,
A447
[Decel Time x] 0.00/600.00 s 0.01 s 10.00 s
Time for the drive to ramp from P044 [Maximum Freq] to 0.0 Hz if Decel Time x is selected.
Decel Rate = [Maximum Freq] / [Decel Time]
A448,
A450
A452,
A454
[Skip Frequency x] 0.0/500.0 Hz 0.1 Hz 0.0 Hz (Disabled)
Works in conjunction with A449, A451, A453 and A455 [Skip Freq Band x] creating a range of frequencies
at which the drive does not operate continuously
A449,
A451
A453,
A455
[Skip Freq Band x] 0.0/30.0 Hz 0.1 Hz 0.0 Hz
Determines the band around A448, A450, A452 and A454 [Skip Frequency x].
A456
A468
[PID x Trim Hi] 0.0/500.0 Hz 0.1 Hz 60.0 Hz
Scales the upper value of the trim frequency when trim is active.
A457
A469
[PID x Trim Lo] 0.0/500.0 Hz 0.1 Hz 0.0 Hz
Scales the lower value of the trim frequency when trim is active.
= Stop drive before changing this parameter.
= Parameter is specific to PowerFlex 525 drives only.
No. Parameter Min/Max Display/Options Default
PF 525
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