Emerson unidrive sp User Manual page 106

Parameter Keypad and
Menu 4
structure display
Motor total
current (Pr 4.01)
as a percentage
of motor rated
It protection operates in this region 2
current
105%
70%
Open loop: Proportion of rated frequency Pr 5.06.
Closed loop: Proportion of rated speed Pr 5.08.
Rated current (Pr 5.07 or Pr 21.07) ≤ maximum Heavy Duty rating.
If the rated current is above the maximum Heavy Duty rating then Pr 4.25 can also be used to select 2 alternative protection characteristics. Both
characteristics are intended for motors where the cooling effect of the motor fan reduces with reduced motor speed, but with different speeds below
which the cooling effect is reduced. The maximum value for K is 1.01, so that above the knee of the characteristics the motor can operate
continuously up to 101% current. (In Regen mode K = 1.01 over the whole operating frequency range).
Motor total
current (Pr 4.01)
as a percentage
of motor rated
It protection operates in this region 2
current
101%
70%
15%
Open loop: Proportion of rated frequency Pr 5.06.
Closed loop: Proportion of rated speed Pr 5.08.
Rated current (Pr 5.07 or Pr 21.07) > maximum Heavy Duty rating.
When the estimated temperature reaches 100% the drive takes some action depending on the setting of Pr 4.16. If Pr 4.16 is 0, the drive trips when
the threshold is reached. If Pr 4.16 is 1, the current limit is reduced to (K - 0.05) x 100% when the temperature is 100%. The current limit is set back
to the user defined level when the temperature falls below 95%. In servo and regen modes the current magnitude and the active current controlled by
the current limits should be similar, and so this system should ensure that the motor operates just below its thermal limit.
The time for some action to be taken by the drive from cold with constant motor current is given by:
T = -(Pr 4.15) x ln(1 - (K x Pr 5.07 / Pr 4.01)
trip
Alternatively the thermal time constant can be calculated from the trip time with a given current from:
Pr 4.15 = -T / ln(1 - (K / Overload)
trip
For example, if the drive should trip after supplying 150% overload for 60 seconds with K = 1.05 then
Pr 4.15 = -60 / ln(1 - (1.05 / 1.50)
106
Parameter Parameter
x.00 description format
Motor speed as a
50% 100%
percentage of base speed
Motor speed as a
50% 100%
percentage of base speed
2
)
2
)
2
) = 89
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Advanced parameter
Macros
descriptions
Max. permissible
continuous
current
Pr 4.25 = 0
Pr 4.25 = 1
Max. permissible
continuous
current
Pr 4.25 = 0
Pr 4.25 = 1
Serial comms Electronic
Performance RFC mode
protocol nameplate
Unidrive SP Advanced User Guide
Issue Number: 10