Technical data

ManualsBrandsDanfoss ManualsMedia ConverterVLT 5000 FLUX

MG.10.Q1.5B – VLT is a registered Danfoss trade mark

VLT 5000/5000 FLUX SyncPos Quick-Setup

This feature is also very helpful in applications where

the power to the motor is turned off and on while the

option card is controlling the VLT. Cutting of power to

the motor (by setting terminal 27 low) while little posi-

tioning deviance is present in the controller, could result

in an enormous control signal being generated once

the power is turned back on.

Velocity Feed-forward FFVEL (36)

The

Velocity feed-forward Velocity feed-forward

Velocity feed-forward factor is a scaling factor

that is multiplied with the derivative of the setpoint

position (the velocity of the setpoint). The result of

this operation is added to the overall control signal.

This feature is especially useful in applications where

there is a good correlation between the control

signal (the VLT speed reference), and the speed of

the motor. This is indeed the case with most

applications using an asynchronous motor.

NB!

The scaling of the FFVEL parameter is de-

pendent on the correct setting of the maxi-

mum reference (VLT parameter #205) as well as the

SyncPos parameters VELMAX (1) and ENCODER

(2).

Acceleration Feed-forward FFACC (37)

The

Acceleration feed-forward factor Acceleration feed-forward factor

Acceleration feed-forward factor is multiplied

with the 2nd derivative of the setpoint position (the

acceleration of the setpoint) and the result is added

to the control signal. This feature should be used to

compensate for the torque used to accelerate/

decelerate the system inertia.

NB!

Scaling of the FFACC factor is depending on

the setting of the

Shortest ramp time Shortest ramp time

Shortest ramp time (31).

You should therefore increase the FFACC accor-

dingly when decreasing SyncPos parameter

Shortest ramp time Shortest ramp time

Shortest ramp time (31) and vice versa.

Sampling time for the entire control algorithm TIMER

(14)

For particularly slow systems you can slow down

the entire control system by entering multiples of

1 ms as the sampling time. However, it is important

to remember that such a change influences all the

control parameters!

Therefore, normally you should not deviate from

the value of 1 ms.

BANDWIDTH

Bandwidth Bandwidth

Bandwidth of 1000 means that the set value is

being executed 100%, thus

DerivativeDerivative

Derivative,

Proportio-Proportio-

Proportio-

nal nal

nal and

Integral factorsIntegral factors

Integral factors are effective as defined.

But if you are operating a system which could be

jeopardized by vibrations, for example, a crane

with a heavy load then you can limit the bandwidth

in which the PID controller should function.

BANDWIDTH (35) of 300 makes a limitation of 30%

possible. The build-up of a vibration is thus pre-

vented since the control is only moved to with 30%

of the calculated set value.

However, then it is necessary also to use the feed-

forward part of the controller in order to achieve

the corresponding control.

10 steps to optomise the PID loop