The UNI3405 Unidrive has 4 essential Modes:
1. Open Loop mode (OL)
For use with standard AC induction motors. The UNI3405 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 performance 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.
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 should used for multi-motor applications. Typically 100% torque at 4Hz.
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 at 1Hz.
2. Closed loop vector mode (VT)
For use with induction motors with a speed feedback device fitted. The UNI3405 directly controls the speed of the motor using the feedback device to ensure the rotor speed is exactly as demanded. Motor flux is accurately controlled at all times to provide full torque all the way down to zero speed. Typically 175% torque at 0rpm.
3. Servo (SV)
For use with permanent magnet brushless motors with a speed and position feedback device fitted. The Unidrive directly controls the speed of the motor using the feedback device to ensure the rotor speed is exactly as demanded. Flux control is not required because the motor is self excited by the permanent magnets which form part of the rotor. Absolute position information is required from the feedback device to ensure the output voltage is accurately matched to the back EMF of the motor. Typically 175% torque at 0rpm
For use as a regenerative front end for four quadrant operation. Regen operation allows bi-directional power flow to and from the AC supply. This provides far greater efficiency levels in applications which would otherwise dissipate large amounts of energy in the form of heat in a braking resistor. The harmonic content of the input current is negligible due to the sinusoidal nature of the waveform when compared to a conventional bridge rectifier or thyristor front end.