Menu 4
Parameter
structure
Keypad and
display
Parameter
x.00
Parameter
description format
Advanced parameter
descriptions
Macros
Serial comms
protocol
Electronic
nameplate
Performance RFC mode
90
Unidrive SP Advanced User Guide
www.controltechniques.com Issue Number: 10
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
In this mode of operation the drive only requires 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 magnetizing 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 Rs (stationary test),
σ
L
s
(stationary test), and L
s
(rotating test). See Pr
on page 117 for details.
5.6.2 Closed-loop
vector
In this mode the drive operates in the rotor flux reference frame. The maximum normal operating current is controlled by the current limits.
DRIVE_CURRENT_MAX is full scale current feedback, i.e. Kc / 0.45.
The relationship between the voltage and current for Closed-loop vector operation is shown in the following vector diagram.
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
MOTOR1_CURRENT_LIMIT_MAX is used as the maximum for some parameters such as the user current limits. The magnetizing current (isx)
remains constant except in field weakening where it is reduced to control the motor voltage. The maximum current limit is defined as follows (with a
maximum of 1000%):
Where:
Motor rated current is given by Pr
5.07
ϕ
1
= cos
-1
(PF) -
ϕ
2
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 either (1.75 x Kc) 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, otherwise it is (1.1 x maximum Normal Duty current rating).
ϕ
1
can be derived directly by the drive auto-tune. However, if the auto-tune is not carried out
ϕ
1
is derived from
ϕ
2
and the power factor. It should be
noted that the drive autotune would make the total y axis voltage under rated load conditions equal to the rated voltage (V
R
), therefore
ϕ
2
is given by
the following equation.
Rotor flux
Closed-loop
vector mode
ϕ ≈
cos (PF)
-1
R i
s sx
i
sy
ϕ
1
ϕ
2
i
sx
R i
s sy
W
L i
mr
s sy
σ
W L i
(steady
state)
mr s sx
v
s
i
s
MOTOR1_CURRENT_LIMIT_MAX
Maximum current
Motor rated current
-------------------------------------------------------
2
cos(
ϕ
1
)
2
1
–
+
cos
ϕ
1
( )
-----------------------------------------------------------------------------------------------------------------
100%
×
=
ϕ
2
-tan
1
–
R
s
I
sxR
2
π
f
R
σ
L
s
I
syR
–
V
R
-----------------------------------------------------------
=
Summary of Contents for unidrive sp
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