Application Tips
Soft Start

Soft starting of any application protects the mechanical drive system by reducing wear and tear on bearings, belts, etc. Soft starting also reduces direct on line starting currents from 600% to 100 – 150% of motor rated current.

Motor-Drive Selection

The number one problem experienced by inexperienced drive users is matching the motor and drive voltage; ensure that the motor terminal box connection (star or delta) corresponds with the drive voltage.

Low Speed Motor Operation

When an application requires a motor to run for long periods of time at low speeds, typically less than 1/3 base speed, and particularly when additional boost is applied, the motor should be force cooled.


Good cable management is the key to solving EMC problems. Always use screened cable between the drive and the motor and keep control and power cabling separated by at least 100mm (4.0″). Where control and power cables must cross, ensure that they do so at 90 degrees (perpendicular).


Soft starting is key in reducing generator costs as a system can be dimensioned for continuous rather than start-up operation (4 – 6 times reduction). A contactor should be placed between the generator and the drive, which should be activated by the Optidrive’s drive healthy output relay. Thus, in the event of a generator over-voltage, the drive will trip causing the contactor to open removing the potentially harmful over-voltage from the drive.

Freewheeling Fans

Use dynamic braking on enable to bring free-wheeling fans to rest before starting to control. Starting a drive into a free-wheeling motor creates a direct short-circuit, which damages the drive and the motor.

Variable Torque (radial & axial fans)

Variable torque mode can be used to drive radial fans and pumps. When selected, an extra frame size of continuous power is available from a particular drive (size 3 and above). Axial/ centrifugal fans or pumps should be driven in constant torque mode/ 150%overload.

Single Phase Supplies

Optidrives offer high power Single Phase Input, with Single Phase Output operation up to 1.5 HP and Three Phase Output operation up to 3.0 HP.

Energy Saving

In general, reducing the speed of a process will save energy. Using PI feedback control, energy savings can be maximized by running a motor at its optimum speed for a particular situation.


In most controlled systems, a display of the controlled parameter is required (i.e., pressure or temperature). Optiport offers both the feedback control logic and a remote mountable, scalable display.


Drives inherently create harmonic distortion. However, the effects can be significantly reduced using input / line chokes. 12 pulse systems can be employed to further reduce harmonic distortion.

Enclosure Design

Drive system enclosure design requires a compromise between (1) managing the heat created by the drive(s) in order to keep the enclosure cool to increase component lifetime, and (2) the need to seal the enclosure for environmental and safety reasons. “Through hole” mounting where the heatsink is put through a hole in the panel allows the sensitive control electronics to be totally sealed in the front of the panel, while the heat generating components in the rear of the panel can be kept cool with “dirty” air.

Long Cables

Ideally, a drive should be placed as close as possible to the driven motor. Where long cables are unavoidable, and particularly, when the cable is longer than the specified maximum for the drive, output filters should be used.

Parallel Motors

When parallel motors are connected to a drive the extra capacitance of the parallel motors compared to a single motor of the same combined power can cause problems.  Allow 10 – 15% extra for drive sizing. In addition, the capacitance effect can be reduced if the motor cabling is “daisy chained” (i.e., connected from the drive to motor 1, then motor 1 to motor 2, etc.) rather than each motor being connected directly to the drive output. In extreme cases, the use of output filters is advisable.