Generally the drive rated current is higher than the matching motor rated current allowing a higher level of overload than the default setting. The time

allowed in the overload region is proportionally reduced at very low output frequency on some drive ratings.

NOTE

The maximum overload level which can be attained is independent of the speed.

2.4

Operating modes

The drive is designed to operate in any of the following modes:

Open loop mode

Open loop vector mode

Fixed V/F mode (V/Hz)

Quadratic V/F mode (V/Hz)

RFC - A

Without position feedback sensor (Sensorless)

RFC - S

Without position feedback sensor (Sensorless)

2.4.1

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.

Quadratic 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.

2.4.2

RFC-A mode

Rotor Flux Control for Asynchronous (induction) motors (RFC-A) encompasses closed loop vector control without a position feedback device.

Sensorless mode provides closed loop control without the need for position feedback by using current, voltages and key operating 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.

2.4.3

RFC- S

Rotor Flux Control for Synchronous (permanent magnet brushless) motors (RFC-S) provides closed loop control without a position feedback device.

For use with permanent magnet brushless motors without a feedback device installed.

Flux control is not required because the motor is self excited by the permanent magnets which form part of the rotor.

Full torque is available all the way down to zero speed, with salient motors.

Electrical

Getting

Basic

installation

started