Gear Drive

The most basic drive solution is the Flottweg gear drive. An electric motor drives the bowl via V-belt drive-either directly or through a fluid coupling to limit the start-up motor current. A second parallel V-belt drive powers a cycloid planeta-ry gear and generates the different-tial speed of the scroll. Both, the bowl and the scroll speed can be adjusted independently with the machine at standstill by changing the twin V-belt pulleys.

Hybird Drive

In this version, an electric motor drives the bowl by means of a V-belt drive, while the scroll is driven by a rotary hydraulic motor power-ed by a compact hydraulic pump unit. The scroll speed and thus the differential speed is infinitely varia-ble during the operation of the cen-trifuge by adjusting the flow rate of the hydraulic fluid between pump and motor. The supply pressure in the hydraulic system is directly proportional to the torque output of the hydraulic motor driving the scroll, and this in turn is directly proportional to the amount of solids the scroll has to convey.

This relationship permits to use a control loop, which regulates the differential speed of the scroll as a function of the solids loading in the centrifuge. As scroll torque rises, the differential speed of the scroll is increased proportionally. This ensures that the amount of solids deposited in the bowl remains constant thus establishing stable operating conditions to achieve uniform dryness of the discharged solids.

Hydraulic Drive

In the Flottweg hydraulic drive configuration both, the bowl and the scroll are driven by separate hydraulic motors connected to a common pump unit. It combines the features of the hybrid drive with the benefits of a variable bowl speed and adjustable start-up times. Through the ability of regulating bowl and scroll speed indepen-dently, optimum "product-speci-fic" processing conditions can be selected.

Both, the Flottweg hydraulic drive and the Flottweg hybrid drive, offer particular advantages for applica-tions in hazardous locations, and also in mobile processing systems.

Frequency
Inverter Drive (VFD)

The Flottweg frequency inverter drive is a refinement of the gear drive. The main drive motor together with a variable frequency inverter provides the capability of an infinitely adjustable bowl speed. The differential speed, which is usually fixed by the speed ratio of the V-belt drives, can be modified at standstill by changing the pulleys.

Backdrive with Dual-VFD

The Flottweg backdrive with dual frequency inverter control is an alternative to the Flottweg hydraulic drive. In this configuration the cen-trifudge is provided with a gear drive that is powered by two motors with VFD's separately driving the bowl and the scroll respectively. The special variable frequency inverters are power-linked via a regenerative circuit.
The drive systems are equipped with an analog closed-loop control device that, above a certain limit, controls the differential speed as a function of the scroll torque. This ensures optimum loading of the cen-trifuge for reaching maximum, uniform dryness of the discharged solids cake even at varying feed conditions. In the case that the torque on the scroll exceeds pre-set values, the electric control system will ultimately shut both the feed and the centrifuge down.

SIMP-Drive ®

The SIMP-DRIVE® (S=simplistic, I=innovative, M=modular, P=pow-erful) constitutes the new generation of Flottweg's dual frequency inver-ter back drive concept.
That new electric drive arrangement represents the equivalent to the proven hydraulic and hybrid drive configurations. The main feature of this new concept is Flottweg's highly innovative special multi-stage planetary gear that allows the use of commercial frequency inverters for the scroll drive electric motor as well as for the bowl drive.
The torque/current of the scroll drive motor is proportional to the torque on the decanter scroll created by the quantity of settled solids inside the centrifuge bowl.
Contrary to the more commonly used dual frequency inverter arran-gements, the SIMP-DRIVE® does not need brake energy regeneration and, therefore, reduces overall power consumption of the centrifuge.
The scroll drive motor supplies only as much power as is required for conveying the solids through the machine.
A simple, analog control loop allows for automatic adjustment of the scroll speed depending on the solids loading in the centrifuge