8 Unidrive M200/201 Control Quick Start Guide
Issue Number: 4
2Introduction
Unidrive M200/M201 delivers substantial communications and application integration through
optional RS485 plus a wide range of industry standard fieldbus and I/O SI modules. Enhances
machine up-time and performance with it’s remote control monitoring.
2.1 Operating modes
The drive is designed to operate in any of the following modes:
1. Open loop mode
Open loop vector mode
Fixed V/F mode (V/Hz)
Square V/F mode (V/Hz)
2. RFC - A
Without position feedback sensor
2.1.1 Open loop mode
The drive applies power to the motor at frequencies varied by the user. The motor speed is a result of
the output frequency of the drive and slip due to the mechanical load. The drive can improve the
speed control of the motor by applying slip compensation. The performance at low speed depends
on whether V/F mode or open loop vector mode is selected.
Open loop vector mode
The voltage applied to the motor is directly proportional to the frequency except at low speed where
the drive uses motor parameters to apply the correct voltage to keep the flux constant under varying
load conditions.
Typically 100 % torque is available down to 1 Hz for a 50 Hz motor.
Fixed V/F mode
The voltage applied to the motor is directly proportional to the frequency except at low speed where a
voltage boost is provided which is set by the user. This mode can be used for multi-motor
applications.
Typically 100 % torque is available down to 4 Hz for a 50 Hz motor.
Square V/F mode
The voltage applied to the motor is directly proportional to the square of the frequency except at low
speed where a voltage boost is provided which is set by the user. This mode can be used for running
fan or pump applications with quadratic load characteristics or for multi-motor applications. This
mode is not suitable for applications requiring a high starting torque.
2.1.2 RFC-A mode
Rotor flux control provides closed loop control without the need for position feedback by using
current, voltages and key motor parameters to estimate the motor speed. It can eliminate instability
traditionally associated with open loop control such as operating large motors with light loads at low
frequencies.
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