Siemens EK 726 Series Servisní příručka stáhnout pdf (Strana 18)

TECHNICAL DESCRIPTION

MICROMASTER

MICROMASTER Vector

MIDIMASTER Vector

SIEMENS DA 64 – 2002/2003

Version D 2/4

Frequency (Hz)

2.5

Constant current + orientation range

Fully-orientated Vector control

Constant current range

200

The above diagram illustrates the operating ranges of the

MICRO/MIDIMASTER Vector sensorless vector control.

Whereby the frequency range of the vector control lies

between 5Hz and 200Hz; V/Hz control is automatically

selected for values outside this range.

Constant current range

In this range, the drive inverter behaves just like a current

source and outputs the current value, programmed in parameter

P083, independent of the particular load.

For instance, for a 750 W motor, if P083 is set to 3.4 A then

the motor current remains independent of the motor load (full

or no load) at 3.4 A.

Constant torque (P078) and breakaway torque (P079) lie in

this range and offer a torque capability of up to 250 %.

This range is below approx. 5 Hz (while the output frequency

ramps-up from zero) and below 2.5 Hz (while the output

frequency ramps-down from a frequency above 5 Hz). The

2.5 Hz hysteresis bandwidth prevents oscillation between the

two operating modes. The specified 2.5 Hz and 5 Hz values

approximately correspond to 5 % or 10 % of the value,

programmed in P081 – the nominal rating plate frequency of

the motor.

Constant current and orientation range

When operating in this range, and the output frequency is

being ramped-up, the back EMF of the motor establishes

itself. The system searches and locks onto the rotor speed

using this information. Once locked, it will remain locked until

the output frequency is reduced to below 2.5 Hz. The slip

compensation is also active in this range.

Fully-orientated vector control

In this range, the drive inverter has determined the operating

state of the motor and maintains the frequency setpoint

within the operating range of the drive inverter. Deviations in

the ambient temperature, the stator resistance, motor slip

etc. are fully compensated over the complete load range and

beyond.

The sensorless vector control is a real, closed-loop control which

is highly dependent on the correctness of the data stamped on

the motor rating plate as well as the accuracy of the inverter's

current monitoring.

When using the sensorless vector control (SVC, Sensorless

Vector Control), the data stamped on the rating plate of the

squirrel-cage induction motor must be precisely entered

(parameters P080 to P085). These parameters are set in the

factory to the data of a four-pole Siemens 1LA5 motor. This data

must be appropriately changed when using another motor. After

the SVC mode has been activated (P077=3), when the drive

inverter is powered-up the next time, the CAL message is

displayed for several seconds. During this time, the drive

inverter optimizes itself and computes the properties and

characteristics of the motor model, for example, the stator

resistance, leakage inductance, thermal time constant of the

rotor and stator.

The calibration routine (CALibration) must be

performed with the motor in a cold state. This is

because the drive inverter automatically compensates

for motor temperature changes.

SVC can only be used for induction motors and for single

motor drives or multi-motor drives with a mechanically

coupled load.

SVC cannot be used for:

· Synchronous or reluctance motors

· Multi-motor drives, group drives (where several motors

are connected in parallel at the output of the drive

inverter)

· Motors with rated outputs less than half the rated drive

inverter output

· Motors with a higher current demand than the drive

inverter can supply, i.e. I

Motor

> P083 max.

In cases such as these, a V/Hz characteristic must be

parameterized;

· P077 = 0 for applications with linear torque

characteristics

· P077 = 2 for applications with pump or fan

characteristics (square-law torque characteristics,

variable torque, VT).

The "Flying start" feature in both MICROMASTER Vector and

MIDIMASTER Vector depend on the vector algorithm and

therefore are subject to the same principles as for SVC

operation.

The restrictions, mentioned above, also apply to drive

inverters, which are configured for operation in the FCC

mode (Flux Current Control) (P077=1). This function was

kept in the vector range in order to guarantee downwards

compatibility with earlier MICRO and MIDIMASTER

generations.

For MIDIMASTER, when a load with square-law torque

characteristic is connected, a significantly higher motor

current is permissible whereby, in almost all cases, the rated

output is achieved using the next larger motor (the motor

current can also be increased using parameter P083).

For a specific output, fan and pump drives can use a lower-

rating drive inverter.

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