Category Archives: Control Techniques

Unidrive Sizing

Control Techniques UNI3405 Unidrive

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.

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 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

4. Regen

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.

Unidrive Sizing Chart –
Unidrive Sizing
Unidrive Sizing
If you are interested in ordering a replacement Unidrive, please call 1-800-691-8511, or email

Control Techniques Unidrive UNI1405

Visit our UNI1405 Product Page for Purchasing Information

The incredibly versatile UNI1405 was one of the first universal AC drive capable of providing V/Hz, open and closed loop vector, servo and regenerative control in every unit. It combines all five AC drive technologies so you only have to learn one drive, support one drive and inventory one drive. For quick setup of basic applications, the Unidrive’s most common parameters are arranged in one concise menu. Hundreds of user-configurable functions separated into 20 logical menus provide quick setup for advanced application. For positioning, ratio control, camming and multi-axis systems, plug-in option modules easily extend the UNI1405’s capabilities. High horsepower Unidrives cover the range from 200 to 1600 HP. The 300 amp power module and control pod (the “brain”) are available as components. They are also available as a packaged drive solution that includes fusing and a disconnect. (See our Packaged Drive Section, pages 120-123 and 128-133.) With the Unidrive’s extensive selection of communication, application, feedback and I/O modules, you can easily upgrade the performance of your drive. Yet, it is simple to configure by using the drive keypad, a remote keypad (CTKP), or UniSoft, our Windows based drive set-up tool. You can tailor each Unidrive to be the drive you want when you want it.

Motion Control & Regen Applications

The UNI1405 is suited for use with AC brushless servo motors. Servo control is ideal for applications requiring load transfer to and from any position, at any speed. The Unidrive is designed for both stand-alone and multi-axis system applications.

In regen mode, two standard Unidrives operate together to provide full four-quadrant control of an AC motor. The system consists of two basic sub-systems, one being a Unidrive operating in any of its standard operating modes (open loop, vector or servo), and the other is a Unidrive operating in its regenerative mode. The link between the two sub-systems is simply the DC bus connections. In this mode, the Unidrive is capable of either supplying power to the DC bus of the Unidrive controlling the motor or removing power from the DC bus of the Unidrive controlling the motor and returning it back to the power line.

Please call 1-800-691-8511 or e-mail for a UNI1405 price quote or for more information on Control Techniques products.



UNI1403 Manual Anthologies

Here at MRO Stock, we sell New and Remanufactured UNI1403‘s, and offer a competitive Repair and Exchange Program.

This blog post will outline how Unidrive UNI1403 module in servo mode may be used in the following system configurations:

a) As a stand alone servo drive, possibly as part of a motion system using analog reference for velocity or torque control. An Axima multi axis position controller is a good example of this type of application.

b) With a UD7x co processor large option module.

Continue reading UNI1403 Manual Anthologies