Menu 4 Introduction
Parameter
x.00
Parameter
description format
Keypad and
display
Serial
communications
CT Modbus
RTU
PLC Ladder
programming
CTSoft Menu 0
Advanced parameter
descriptions
64 Commander SK Advanced User Guide
www.controltechniques.com Issue Number: 9
Definitions:
v
s
= motor terminal voltage vector
i
s
= motor current vector
i
sy
= y axis component of current
i
sx
= x axis component of current
v* = no load y axis voltage reference
MOTOR1_CURRENT_LIMIT_MAX is used as the maximum for some parameters such as the user current limits. This is defined in the vector
equation as follows (with a maximum of 1000%):
Where:
Motor rated current is given by Pr 5.07
PF is motor rated power factor given by Pr 5.10
(MOTOR2_CURRENT_LIMIT_MAX is calculated from the motor map 2 parameters)
The Maximum current is (1.5 x Rated drive current) when the rated current set by Pr 5.07 (or Pr 21.07 if motor map 2 is selected) is less than or
equal to the Maximum Heavy Duty current rating specified in Pr 11.32, otherwise it is (1.1 x Maximum motor rated current).
For example, with a motor of the same rating as the drive and a power factor of 0.85, the maximum current limit is 165.2%.
The above calculation is based on the assumption that the flux producing current (Pr 4.17) in the stator flux reference frame does not vary with load
and remains at the level for rated load. This is not the case and the flux producing current will vary as the load is increased. Therefore the maximum
current limit may not be reached before the drive reduces the current limit to prevent the peak limit from becoming active.
The rated active and rated magnetising currents are calculated from the power factor (Pr 5.10) and motor rated current (Pr 5.07) as:
rated active current = power factor x motor rated current
rated magnetising current = √(1 - power factor
2
) x motor rated current
The drive uses the motor rated current and the power factor at rated load to set up the maximum current limits, scale the current limits correctly and
calculate the rated active and magnetising currents. The user may enter the nameplate values in Pr 5.07 and Pr 5.10 respectively and the drive will
operate satisfactorily. Alternatively the drive can perform an auto-tune test on the motor to measure the power factor at rated load by measuring R
s
(stationary test), σL
s
(stationary test), and L
s
(rotating test). See Pr 5.12 on page 77 for details.
On Commander SK sizes 2 to 6, the ratio between maximum continuous current and maximum overload is less than on the smaller drives. This is
handled in the software by specifying the 'drives rated current' as maximum current limit level / 1.5, the same as on the smaller drives. The current
rating in Pr 11.32 is still the Heavy Duty rating of the drive, but because it is greater than the 'drive rating' figure used by the software, the current limit
point will be less than 150% of the rating specified in Pr 11.32.
The motor rated current (Pr 5.07) may be increased above the drive current rating specified in Pr 11.32 up to a limit defined by the Maximum motor
rated current. If the motor rated current is above the current rating specified in Pr 11.32, the motor thermal protection scheme is modified (see
Pr 4.16).
In the following descriptions the term 'drive rated current' is the one used by the software, not the value in Pr 11.32.
This parameter is the r.m.s. current from each output phase of the drive. The phase currents consist of an active component and a reactive
component. The three phase currents can be combined to form a resultant current vector as shown below:
The resultant current magnitude is displayed by this parameter. The active current is the torque producing current, and the reactive current is the
magnetising or flux producing current.
4.01 Current magnitude (motor current) {88}
Coding
Bit SP FI DE Txt VM DP ND RA NC NV PT US RW BU PS
1 121 1 1 1
Range 0 to DRIVE_CURRENT_MAX
Update rate Background
MOTOR1_CURRENT_LIMIT_MAX
Maximum current
Motor rated current
-------------------------------------------------------
2
PF()
2
1–+
PF
--------------------------------------------------------------------------------------------------------
100%×=
Resultant
output current
Pr
4.01
Reactive current
Pr
4.17
y
x
Active current
Pr
4.02
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