78
Mentor MP User Guide
www.controltechniques.com Issue: 3
8 Optimization
Before attempting to tune the drive the following data is required
•
Armature full load current
•
Armature voltage
•
Field current
•
Field voltage
•
Base speed
•
Maximum speed
In the following worked example the data below has been used
•
Armature full load current = 67A with an overload of 90A for up to 30
seconds
•
Armature voltage = 500V
•
Field current = 1.85A
•
Field voltage = 300V
•
Base speed = 1750 rpm
•
Maximum speed = 2500rpm
8.1 Armature current
•
Set the motor rated current in Pr
5.07
(
SE07, 0.28
) to 67A.
•
Set current limits in Pr
4.05
and Pr
4.06
to 90/67 x 100 = 134%
•
Set the motor thermal time constant in Pr
4.15
= -30 / ln(1 - (1.05 /
1.34)
2
) = 31.5
8.2 Speed feedback
8.2.1 Estimated speed feedback
For estimated speed feedback set Pr
3.26
(
Fb01, 0.71
) to ESt SPd. This
uses an estimated speed feedback based on the motor back emf, motor
rated speed, motor rated voltage, armature resistance, armature current
and field flux feedback.
8.2.2 Tachometer speed feedback
For tachometer speed feedback set Pr
3.26
(
Fb01, 0.71
) to tACHO. Set
the tachometer voltage rating in V/1000rpm in Pr
3.51
(
Fb02, 0.72
) and
the tachometer input mode Pr
3.53
(
Fb03, 0.73
) to suit the type of
tachometer used.
8.2.3 Encoder speed feedback
For encoder speed feedback set Pr
3.26
(
Fb01, 0.71
) to drv. Set the
lines per revolution (Pr
3.34
(
Fb05, 0.75
)), encoder supply voltage
(Pr
3.36
(
Fb06, 0.76
)) and encoder type (Pr
3.38
(
Fb07, 0.77
)).
8.2.4 Solutions Module speed feedback
If an Solutions Module is being used to provide speed feedback then
Pr
3.26
(
Fb01, 0.71
) should be set to SLot1, SLot2, or SLot3.
8.3 Field current
The rated field current is set in Pr
5.70
(
SE10, 0.31
). When the field
current equals the compensated rated field current (see Pr
5.74
), 100%
field flux is produced.
8.3.1 Field weakening with a speed feedback device
If field weakening is required the field compensation factor (Pr
5.74
), the
motor saturation breakpoints (Pr
5.29
, Pr
5.30
) and the voltage at which
field weakening is required to begin (Pr
5.59
) must be set.
Setting up the drive in field weakening is straightforward when a speed
feedback device is available. The rotating autotune (Pr
5.12
(
SE13
,
0.34
) = 2) automatically sets up the parameters above. Follow the quick
start commissioning / start-up (from European defaults) as shown in
Table 6-1 on page 64 to set up the drive. Enable field weakening
(Pr
5.64
= On). Save parameters.
For field weakening from USA defaults Pr
5.75
Field voltage mode
should be set to OFF. Pr
5.28
Field weakening compensation disable
should be set to OFF. Follow the quick start commissioning / start-up
(from European defaults) as shown in Table 6-1 on page 64 to set up the
drive. Enable field weakening (Pr
5.64
= On). Save parameters.
8.3.2 Field weakening in estimated speed mode (no
speed feedback device)
The Rotating Autotune (Pr
5.12
(
SE13
,
0.34
) = 2) sets up the field
controller for more accurate flux control and open loop speed accuracy.
The rotating autotune needs to know the motor speed and so a speed
feedback device has to be connected to the drive before a rotating
autotune can be carried out. In some applications a speed feedback
device may not be required and so the procedure below allows the user
to manually adjust the field controller parameters to achieve better open
loop speed control.
•
Follow the quick start commissioning / start-up (from European
defaults) as shown in Table 6-1
on page 64 until a static autotune (Pr
5.12
(
SE13
,
0.34
)
= 1) has been carried out.
•
Set Pr
5.64
Field weakening enable
to On.
•
Ensure that Pr
5.29
, Pr
5.30
, Pr
5.68
and Pr
5.74
are set to their
default values of 50%, 75%, 100% and 100% respectively.
•
Set the speed demand to 1/4 of
Base speed
(Pr
5.08
(
SE08, 0.29
))
and run the machine up to speed and check the speed of the
machine using a hand held device.
•
If the machine speed is lower than 1/4 of base speed (which is
normally the case) adjust the
Field compensation factor
(Pr
5.74
)
down until the correct machine speed is reached. If the machine
speed is higher than
1
/
4
of base speed (only possible if the motor
nameplate field current is low), adjust the rated field current (Pr
5.70
(
SE10, 0.31
)) up until the correct machine speed is reached.
•
Set Pr
5.68
Maximum flux
to 75% and measure the actual speed of
the machine (speed 75)
•
Set Pr
5.68
Maximum flux
to 50% and measure the actual speed of
the machine (speed 50).
•
Stop the machine and set Pr
5.68
Maximum flux
back to 100%.
•
Set Pr
5.29
Motor saturation breakpoint
1 = 50 x set speed / actual
speed (Speed 50)
•
Set Pr
5.30
Motor saturation breakpoint 2
= 75 x set speed / actual
speed (speed 75).
•
Save parameters.
For field weakening from USA defaults Pr
5.75
Field voltage mode
should be set to OFF. Pr
5.28
Field weakening compensation disable
should be set to OFF. The procedure above should then be followed to
set up the drive for field weakening.
8.3.3 Field economy
Field economy can be used to keep the field energized, at a low level of
current (to prevent overheating), when the motor is not running to
prevent condensation forming in the motor. The field economy level and
the timeout can be adjusted.
To use this function it is necessary to set:
•
Set Pr
5.65
to enable the field economy timeout
•
Set Pr
5.67
to the percentage of full field that you want to use in
economy mode e.g 10%.
•
Set Pr
5.66
to the time after the drive enable signal is removed to the
field current reducing to the economy level.
8.4 Current loop gains self-tuning
For optimum performance the current loop must be set-up. The
dynamics of the current loop are principally a function of the electrical
characteristics of a particular motor.
The drive determines the electrical characteristics of the motor by
injecting current into the armature winding.
8.4.1 Static autotune for current loop gains
If Pr
5.12
(
SE13, 0.34
) is set to a 1, the drive is enabled and a run
command is applied in either direction the drive performs a static
autotune test. The test will not start unless the drive is disabled and
before the test is initiated by applying the enable or run, i.e. it will not
start unless the drive is in a stop state.
NOTE
NOTE
Summary of Contents for MP105A4
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