ABB DCS 500B, Description

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Functional Software description
DCS 500 Software Description 25
Scaling of the
actual voltage to
control The function of the analogue tacho generator can be checked by
driving the motor at actual speed which is based on the calculated
EMF. At the mean time the drive’s actual speed is measured by a
manual tachometer and incoming feedback of the analogue tacho
generator can be checked from the output
OUT+ (10101) of AITAC
function block.
Application ex-
ample Example. Let’s suppose that speed reference value 20000 corre-
sponds to 1500 rpm of motor. First a value 15 000 is set to pa-
rameter
SPEED SCALING (2103) . The tacho generator gives +8V
at actual speed 1500 rpm forward and -8V at 1500 rpm reverse.
The actual speed of the motor has to be 1500 rpm with speed ref-
erence 20000, so the
AITAC scaling is made as follows for:
AITAC CONV MODE (101) = 3
AITAC HIGH VALUE (102) = (10V/8V)*20 000=25 000
AITAC LOW VALUE (103) =(10V/-8V)*20 000= -25 000
Actual speed ba-
sed on EMF The EMF (Electromotive Force) speed actual is based on the rela-
tionship of flux, EMF and actual speed. This method can be used
up to the field weakening point. The parameter
U MOTN V (501)
defines the armature voltage of the motor, which corresponds to
the speed value 20000 in the software.
The armature autotuning function calculates the
ARM R (411) and
ARM L(410) parameter values. See paragraph "Autotuning" in this
chapter.
Calculation of
speed from the
EMF
Q 8GF
5 , / G, GW
)/8;
$ $ $ $ =
− +
( * * / )
The resistive voltage drop ARM R (411) is calculated:
ARM R RA
I CONV A
U SUPPLY
=
22444
10509
507
* *
( )
( )
Ω
where RA [
Ω
] = armature resistance
The inductive voltage drop ARM L(410) is calculated:
ARM L
LA mH I CONV A
U SUPPLY scantime *
=
* ( ) *
( )
10509 245
507
where LA [mH] = armature inductance in mH
scan time = 3,33 ms (50 Hz network) or 2,77 ms (60 Hz)
Filtering of the
actual speed Filter time constant for signal SPEED ACT (12102) can be adjusted
by parameter SPEED ACT FTR (2104) . The output of the second
filter SPEED ACT FILT (12103) can be used as display.