Ema-Elfa

Powder Brakes and Clutches

  

Technical description

The electromagnetic powder clutch and brake combine the flexibility of hydraulic clutch with set stability of friction clutch (brake). Torque is transferred by special,alloy, dry ferromagnetic powder whose apparent viscosity can be changed bymodulating the current of electromagnetic coil. The clutch (brake) can withstand continuous slip (within the framework of its empirically set, rated thermal values) atprecisely specified and stable value of torque which is determined by level ofelectromagnet excitation. Slip between input and output member of the clutchis not indispensable for transferring the torque and if load torque does not exceed the value of rotating torque for which the clutch (brake) has been excited, synchronous action will occur.

Conversely, if load torque exceeds level of excitation torque, slip will occur inabsolutely smooth manner with value of torque specified in advance.

For all  practical purposes, coefficients of static and dynamic friction are practicallyidentical, output torque is independent of speed or slip speed.

Powder parameters are insensitive to temperature growth at working surfaces,and the clutch will all the time have the characteristic for which the torque transferredis directly proportional to current. It should be noted that utilization of dry powder instead of wet powder ensures better stability and accuracy of torque regulation.

 

Construction and principle of operation

The clutch (brake) has two concentric members: body containing electromagnetic coil and, inside it and separated by small, ring gap, internal rotor, in case of clutch - its output member. The ring gap contains ferromagnetic powder which undergoes activation when electromagnetic excitation occurs. The resulting stream generated passes through the powder causing its setting in accordance with the stream path through which drive bonding occurs between body and rotor whose force depends exclusively on value of direct current applied to electromagnet coil. Torque transferred by the powder clutch is proportional to excitation current and is changed smoothly from maximum, rated, design value practically to zero for all models.
The characteristic for torque in the current function can change by 5% depending on whether the current rises or falls. This happens as a result of magnetic hysteresis. For all practical purposes, torque is independent of speed, irrespective of whether slip occurs or does not occur, and this torque can be maintained with accuracy of 5% for speed in range of recommended operating speeds from 50 to 3000 rpm. Residual torque while switching off the clutch (brake) occurring as a result of residual circuit magnetism as well as bearing and sealing friction are less than 1% of rated, design torque for any clutch or brake. Torque reaction time is determined by relationship of electromagnet coil inductance to its resistance plus magnetic delay due to losses on rotary current.

Note: To ensure proper operation, all clutches and brakes must be mounted in the horizontal position of the axis.

APPLICATION:

Characteristics of powder clutches and brakes permit universal utilization. Torque transferred and electromagnet excitation current are approximately proportional to each other. For excitation current set to fixed value, torque transferred by the clutch is independent of speed difference of driving and driven shaft. When switching on, torque increases with certain time-lag. Switching off on direct current side gives shorter connecting time than on alternating current side.

Examples of application:

    - at production machine inlet, pulling force in leading/feeding material is to be maintained at constant value,
    - on uncoiler, pulling force in leading/feeding material is to be maintained at constant value,
    - after wire drawing machine, wire winding is to occur with variable drawing force

Through analysis of winder drum diameter, with changing diameter of drum, pulling force is maintained
 at constant value. This ensures simple operation and simultaneous control of the process.

 

  Dane techniczne Technical data P3 .... P6 .... P12 .... P35 .... P65 .... P80 .... P120 ... P170 ...
  Moment nom. Nom. Torque 3 Nm 6 Nm 12 Nm 35 Nm 65 Nm 80 Nm 120 Nm 170 Nm
  Moment resztkowy Residual Torque 0.10 Nm 0.15 Nm 0.3 Nm 0.4 Nm 0.65 Nm 0.8 Nm 1,2 Nm 1,7 Nm
  Napięcie zasilania Supply voltage 24 VDC 24 VDC 24 VDC 24 VDC 24 VDC 24 VDC 24 VDC 24 VDC
  Natężenie prądu Current intesity 0.8 A 0.96 A 0.92 A 1 1 1,1 A 1.2 A 1.2 A
  Oporność Resistance 30 Ohm 25 Ohm 26 Ohm 24 Ohm 24 Ohm 22 Ohm 21 Ohm 21 Ohm
  Czas włączenia t 09 Engaging time t 09 170 ms 180 ms 200 ms 350 ms 500 ms 700 ms 760 ms 880 ms
                     
  Czas wyłączenia t 01 Disengaging time t 01 80 ms 90 ms 100 ms 250 ms 250 ms 350 ms 660 ms 940 ms
                     
      P 3 H P 6 H P 12 H P 35 H P 65 H P 80 H P 120 H P 170 H
  Moc rozproszenia Power 50 W 80 W 100 W 150 W 200 W 250 W 400 W 500 W
  Masa Weight 0,75 kg 1,4 kg 2.6 kg 5.0 kg 9.0 kg 12.7 kg 18 kg 24 kg
      P 3 HR P 6 HR P 12 HR P 35 HR P 65 HR P 80 HR P 120 HR P 170 HR
  Moc rozproszenia Power 100 W 160 W 200 W 280 W 400 W 500 W 800 W 1000 W
  Masa Weight 1,1 kg 1,9 kg 3.8 kg 7.5 kg 13.0 kg 18.5 kg 23 kg 30 kg
      P 3 HV P 6 HV P 12 HV P 35 HV P 65 HV P 80 HV P 120 HV P 170 HV
  Moc rozproszenia Power 150 W 300 W 400 W 600 W 800 W 1050 W 1600 W 2000 W
  Masa Weight 1,4 kg 2,2 kg 4.5 kg 8.0 kg 13.0 kg 17.0 kg 24 kg 28kg
      P 3 S P 6 S P 12 S P 35 S P 65 S P 80 S P 120 S P 170 S
  Moc rozproszenia (500 rpm) Power (500 rpm) 80 W 100 W 120 W 250 W 280 W 350 W 800 W 1000 W
                     
  Moc rozproszenia (1000 rpm) Power (1000 rpm) 100 W 120 W 150 W 250 W 350 W 550 W 1000 W 1250 W
                     
  Masa Weight 0,8 kg 1,5 kg 2.8 kg 5.2 kg 9.4 kg 13.3 kg 18,9 kg 24,8 kg
      P 3 SR P 6 SR P 12 SR P 35 SR P 65 SR P 80 SR P 120 SR P 170 SR
  Moc rozproszenia (500 rpm) Power (500 rpm) 250 W 350 W 440 W 640 W 960 W 1200 W 1600 W 2200 W
                     
  Moc rozproszenia (1000 rpm) Power (1000 rpm) 300 W 400 W 500 W 800 W 1200 W 1550 W 2000 W 2750 W
                     
  Masa Weight 1,2 kg 2,0 kg 4.0 kg 7.7 kg 13.4 kg 19.0 kg 23,7 kg 28,8 kg

 



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