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The amplifier for an electrodynamic shaker is actually a system that performs multiple functions, including:

  • Amplify the drive signal from an external vibration controller and apply it to the shaker’s voice coil
  • Provide a constant DC current to the shaker’s field coils
  • Provide 3-phase power to the blower
  • Facilitate safe and orderly start-up and shut-down of the shaker system
  • Monitor safety interlocks and respond appropriately and rapidly to any “trips”
  • Display the status of the system
  • Maintain armature mid-point position under static and dynamic conditionals (with optional AAC)

Sentek Dynamics PA Series amplifiers are air-cooled and modular. The shaker voice coil is driven by a digital (Class D) switching amplifier. This switching amplifier is comprised of multiple 12 kVA power-modules working in parallel, driven by a separate DC source. Each module is comprised of two independent 6 kVA sub-modules. This modular construction provides excellent load-sharing between all of the T-channel MOSFET switching transistors involved and simplifies field maintenance and power upgrades. MOSFET switching at 100 kHz provides excellent resolution, linearity and fidelity. PA Series amplifiers up to 480 kVA are available. All exhibit greater than 90% efficiency, minimizing the heat thrown off by amplifier cabinet. Sentek Dynamics can provide replacement amplifiers for older systems produced by other manufactures.

The PA Series amplifier cabinet serves as the central wiring point. It is powered from a three-phase source (typically 480 VAC ) and provides power to all remaining elements of the shaker system. It also houses the SCU-200 main control panel which serves as a central control point with system status readouts. Interlock sensors assure that the armature position, all voltages, currents, temperatures and blower air-flow (or cooling water parameters) are within normal limits before allowing a test to commence. Any parameter that goes out of range during a test initiates a trip readout and an automated emergency shut-down. An Emergency Stop button is also provided. The optional SA-100 remote control panel is available, providing full system control and readout at a remote location.

Every Sentek Dynamics shaker comes with a mating trunnion base. A trunnion (from the old French trognon or trunk) is a cylindrical protrusion used as a cannon’s mounting and/or pivoting point. This mounting base allows the shaker to be operated in vertical or horizontal orientation (for use with a slip table). The trunnion base supports the shaker at two pivot points, much like a cannon. It is provided with locking bolts to affix the shaker in either orientation. The shaker/trunnion interface is provided with pneumatic isolators to minimize floor vibration. Other isolation options, such as air-isolation feet, pads and mounts are also available. Shakers delivering 6 kN (1320 lb) force and greater can be provided with a motorized gearbox to rotate the shaker.

   
  
 
 
  
    
  
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  A typical high-force water-cooled system including a shaker and mono-base slip-table with air isolation mounts.

A typical high-force water-cooled system including a shaker and mono-base slip-table with air isolation mounts.

   
  
 
 
  
    
  
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   A PA Series amplifier – the control center of your shaker system.

A PA Series amplifier – the control center of your shaker system.

(Click to enlarge) Functional representation of a Class-D switching amplifier. The low-voltage analog Drive input from the VCS is amplified to a high-power level and applied to make the voice coil move.