FNCT fill-control fluid coupling
Hydrodynamic power transmission with fill control — ideal start-up and acceleration control for large drive motors, with electronic control for added safety.
Controlled torque, by oil level.
FNCT fluid couplings work on the principle of hydrodynamic power transmission with fill control. By varying the oil level in the working circuit, the transmitted torque is controlled — making FNCT ideal start-up and acceleration-control equipment for large drive motors.
Combined with electronic control, FNCT couplings provide additional safety to drive motors and precise torque-transmission control — letting heavy, high-inertia machines be brought up to speed gradually, smoothly and shock-free.
Key data
Built around a fixed scoop tube
The impeller (pump) and rotor (turbine) are enclosed in a primary casing, which sits within a secondary casing. A fixed-position scoop tube continuously collects the oil released by the leak-off nozzle from the working circuit.
The impeller and rotor shafts connect to the motor and driven machine through suitable flexible couplings, and rest on ball and roller bearings in dedicated bearing housings. The complete rotating assembly is carried in a robust, self-supported stationary housing of welded construction.
A motor-driven oil pump circulates working oil through the coupling's oil circuit. Two solenoid valves and two non-return valves control the oil level in the FNCT working circuit, while a lube line branching from the pump outlet feeds the bearings continuously, regardless of the working-circuit oil level.
How fill control works
Oil pumped by the motor-driven pump flows into the working circuit through an oil-collection ring. The leak-off nozzle continuously drains oil from the working circuit into the secondary casing, where it is gathered by the fixed scoop tube, passed through an oil cooler and re-circulated.
By operating the solenoid valves, oil is either returned directly to the working circuit or routed back to the tank — so any oil level from 0% (empty) to 100% (full) can be achieved on demand. Since transmitted torque depends on this oil level, torque during starting or running is fully controllable.
The coupling can be declutched at any time by emptying the circuit. During acceleration, an electronic control monitors motor power and machine speed and continuously adjusts the oil level for smooth, gradual run-up.
Why engineers specify FNCT
- No-load start-up of the drive motor — faster decay of starting current and reliable motor protection
- Wear-free power transmission through circulating oil
- Smooth, controlled start-up and acceleration — acceleration time can run up to several minutes
- Gradual, shock-free build-up of breakaway torque
- Clutching and declutching of the driven machine with the motor running
- Damping of shock loads and torsional vibration / oscillation
- Suited to multi-drive conveyors with load sharing and sequential start-up
- Empty belt can be moved at low speed for inspection and adjustment
- Flexible operation with electronic control; oil cooling possible at standstill
- Simple, robust design — easy to operate, low maintenance, dependable in hot and humid conditions
Diagrams & views
Built for heavy, high-inertia drives
FNCT couplings excel at start-up duty and controlled, smooth acceleration of heavy masses and inertia — and are ideally suited to belt and pipe conveyor applications.
Rating table — FNCT
Maximum ratings in KW at different input speeds (RPM). For final selection, please consult Fluidomat application engineering.
| FNCT | 500 | 600 | 720 | 750 | 900 | 1000 | 1200 | 1500 | 1800 |
|---|---|---|---|---|---|---|---|---|---|
| 566 | 12.2 | 21.1 | 36.5 | 41.2 | 71.3 | 97.8 | 168.9 | 330 | 570.2 |
| 655 | 24.8 | 42.9 | 74.1 | 83.7 | 144.7 | 198.5 | 343 | 670 | 1157.2 |
| 750 | 49.6 | 85.7 | 148.2 | 167.5 | 289.4 | 397 | 686 | 1340 | — |
| 810 | 68.7 | 118.7 | 205.2 | 231.9 | 400.7 | 549.7 | 950 | 1500 | — |
Ratings shown are maximum values per frame size. Full dimension tables and oil quantities are available in the FNCT catalogue.
Related couplings & resources
Need controlled start-up for a heavy drive?
Send us your conveyor or mill duty and inertia, and our engineers will recommend the right FNCT size and control package.