The coupling is partially filled with hydraulic oil to a level suitable for the absorbed power of the application and the acceleration characteristics of the driven machinery. 

 

The optimum oil fill is that which just allows the driven machine to accelerate from rest, thus providing the best drive overload protection.

 

Special features:

 

1.High inertia controlled torque to 700 Kw-1500rpm

2.Soft start-motor starts on low load

3.Allows use of standard squirrel cage motors

4.Dampens torsional vibration, reducing mechanical stress – extends machine life

5.Delay fill version – extends acceleration time and reduces start-up torque 

6.Can match load and speed on multi drives

Energy saving through reduced current demand at start-up

7.Coupling and V pulley types -design flexibility

8.Overload protection – fusible plug safeguards equipment 

     If a machine is driven by a squirrel cage motor without the use of hydraulic coupling, the following 

conditions arise[fig 01 ] 

 

      1.Motor will pull out 250/280% FLT.

      2.Motor will consume 6 times FL amps.

      3.Increase in motor temperature.

 

    Star-delta starting reduces overheating. However, the starting torque in start is only 30% that in delta and it is often necessary to use larger or more complicated wound motors, particularly with high inertia machinery.(A=Locked rotor torque , B=Stall torque 250/280%,C=Normal torque 100%,I=Amperage)

 

    When a drive includes a fluid coupling the motor starts on  low load ,with only an instantaneous current peak at switch on [fig 02]. At start up all the motor torque is available to accelerate the motor rotor and coupling impeller (pump).The driven impeller (turbine) increases speed smoothly from zero rpm until the 100% slip curve intersects the motor torque curve at approximately 85% motor speed [ fig 03 ]. When the torque developed by the fluid coupling matches the resisting torque of the driven machine, acceleration of the load commences and continues up to running speed which will be between 94% and 98% of the driving speed depending on the coupling size.