4. Configuration of the frequency converter
4.1. Setting nominal parameters of the motor
Before the first run of the frequency converter it is necessary to determine the nominal parameters of the
electric motor. Appropriate data can be read form the rating plate. It is necessary to enter the following parameters:
Par. 1.1 - nominal power of the motor Pn [kW]
Par. 1.4 - nominal motor voltage [V]
Par. 1.2 - nominal motor speed (rpm)
Par. 1.5 - nominal motor frequency [Hz]
Par. 1.3 - nominal motor current [A]
Par. 1.6 - nominal cosφ of the motor
In the U/f scalar operation modes these data are sufficient to start the frequency converter.
4.1.1. Preparation for operation in a vector control mode
If you want to work in vector mode (with or without an encoder), then the drive must have additional information
about the motor parameters, so-called electric motor equivalent circuit diagram parameters (fig. 4.1):
Parameter 1.11 - resistance of stator windings Rs [Ohm]
Parameter 1.12 - resistance of rotor windings Rr [Ohm] (the parameter 1.12 is defined automatically by
converter MFC710 on basis of other motor parameters - it is impossible to change)
Parameter 1.13 - main inductance Lm [mH]
Parameter 1.14 - inductance of a stator Ls + Lm [mH]
Parameter 1.15 - inductance of a rotor Lr + Lm [mH]
Parameter 1.16 - additional inductance - connecting wires, choke if connected in series with the motor.
In order to determine the values of these parameters,
use the built-in function of the IDENTIFICATION RUN described
in chapter 5.1 “Vector mode. Identification run”. It is also
possible to enter them manually (or to adjust the values
obtained from the identification run).
Without the correct determination of these parameters,
the operation in the vector mode is not possible. Setting of
incorrect values will result in the malfunction of the system.
These parameters correspond to the motor in the star
connection (Us is the phase voltage).
After performing the IDENTIFICATION RUN procedure
or manually entering these parameters, the parameter 1.20 "OPERATING MODE" should be set to:
Vector1 – sensorless mode – does not require an encoder, but it is less accurate,
Vector2 – operation mode with a position sensor (encoder) - the encoder resolution is determined by the
parameter 1.80; this operation mode is especially recommended for operation at low speeds (below 2.0 Hz).
4.2. Control
Main possibilities of converter control – referencing output frequency (rotation rate) and configuration of control
with a START / STOP signal - are described below with additional information about configuration of output relays of a
converter. More detailed information is in „parameter list” - Appendix C. The control possibilities of the converter result
from the analysis of a structure of the control system - fig. 4.2b/4.2c.
4.2.1. Structure of control
The control system of the converter MFC710 uses the structure of two independent „control places” A and B,
that allows to change whole structure of the converter control (sources of START and STOP signals and sources of
frequency for drive operation) by changing only one parameter – 2.1. In fig. 4.2a there is simple diagram and in fig. 4.2b
and 4.2c there are developed diagrams of the converter control.
Fig. 4.2a – The control structure simple diagram
MFC710 User Manual - TWERD Power Electronics
27
Fig. 4.1 – Equivalent circuit of squirrel-cage motor
Rs
Rr
Ls
Lr
Lm
Rr/s
Us
Sources of control
signals
- The control panel
- Analogue inputs
- Digital inputs
- RS
- PID-regulator
- Another sources
Control place A
Choice of a control
source
Par. 2.2 (Ref.-unit)
Par. 2.4 (START)
Control place B
Choice of a control
source
Par. 2.3 (Ref.-unit)
Par. 2.5 (START)
Choice of the
Control place
Par. 2.1
- Blocking
- Constant frequencies
- Strips of a frequencies
cutting
- Constraint of control
with RS
Speed
START /
STOP
