Siemens EK 726 Series Wartungshandbuch PDF herunterladen (Seite 21)

TECHNICAL DESCRIPTION

MICROMASTER

MICROMASTER Vector

MIDIMASTER Vector

SIEMENS DA 64 – 2002/2003

2/7 Version D

2.1.13.1 Features of different control techniques

Mode V/Hz FCC SVC

Digital setpoint resolution

0.01

Analog setpoint resolution

10 bit

Internal frequency resolution

0.01

Speed accuracy

- constant torque

- field weakening range

>2 %

<2 %

)

<5 %

)

£1 %

max

´ f

slip

/10

)

Torque rise time

» 50 ms <25 ms <10 ms

Torque ripple <2 % <2 % <2 %

) With slip compensation

) The slip values of standard motors are typically:

6 % at 1 kW, 3 % at 10 kW, 2 % at 30 kW, 1 % at 100 kW

2.2 Closed-loop PID control

All of the MICROMASTER Vector and MIDIMASTER Vector drive units have, as standard an integrated PID control, which uses the

second analog input as actual value signal input (0 - 10 V or 0 - 20 mA). This therefore provides an accuracy of 10 bit.

MICROMASTER has a closed-loop PI control which uses the digital input for the setpoint and the analog input for the actual value

signal. This function allows closed-loop control of quantities which only change slowly, for instance, temperature or pressure,

without requiring any additional circuitry or software. This means that closed-loop speed control is also possible for slow processes.

The reference value or setpoint is entered directly as a percentage of the controlled variable (0 - 100 %). This means that the

system is insensitive to measured quantities which are received from transducers. Examples of these transducers are, for example,

pressure and flow velocity. The signal, received from the transducer, is transferred to one of the analog inputs where it is compared

with the setpoint. The motor speed is then controlled so that the deviation between the setpoint and actual value is minimized.

Additional features of the PID control:

· Any display scaling can be selected (P010, P001)

· P, I and D factors can be separately defined

· Selectable sampling interval and filtering

· Can be flexibly adapted to the transducer signal

· The motor can be shutdown below a minimum frequency – this can be parameterized (P220)

· A message can be output at the minimum and maximum motor frequency – this can be selected using parameters (relay

output, P061 and P062).

Parameters P201 to P220 are assigned to the PID function.

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