Greetings DIY audio community!
I am trying to design a class D amplifier/driver to power up a shaker table armature with the following parameters: 2 VDC, 550 A max, 0.02 Ohm DC resistance. The existing array of amplifiers has reached end of life and the discrete components are becoming impossible to source. My intent is to evaluate paralleling a number of class-D amps to attain the low load resistance required by the application.
Amplifer inputs:
Amplifier output:
The pre-amplifier is also a bit of a beast and the whole system can likely be simplified, including going away from 180 VDC input.
Very interested to see if this can be done.
I am trying to design a class D amplifier/driver to power up a shaker table armature with the following parameters: 2 VDC, 550 A max, 0.02 Ohm DC resistance. The existing array of amplifiers has reached end of life and the discrete components are becoming impossible to source. My intent is to evaluate paralleling a number of class-D amps to attain the low load resistance required by the application.
Amplifer inputs:
- Power: 180 VDC
- Clock: 56 KHz square wave, 50% duty cycle, 12 VDC peak
- Signal: PWM modulated with 12 VDC peak, produced by class D signal pre-amplifier by combining original 2 V peak-peak audio input with a triangular waveform.
Amplifier output:
- Max Voltage: 2 peak-peak
- Max current: 550 A
The pre-amplifier is also a bit of a beast and the whole system can likely be simplified, including going away from 180 VDC input.
Very interested to see if this can be done.
100% no problem. 10 years ago I had caraudio project powered sub with 160mOhm voice coil, I called that direct-amp i.e. low impedance speaker driven directly from a car's battery with no step-up SMPS. 90A peak at 14.4VDC only 4pcs QFN5x6 25V mosfets without heatsink. 100kHz UcD like amp with extra loop filter, $8 B.O.M. You can see it as kicker/rockford/blaupunkt/jl etc powered subs. Further, I had the idea to implement "zero ohm" voice coil with moving magnet system but gave it up.
I'm afraid the electrical specification does not list these parameters, so they would likely need to be empirically determined. The operating frequency, however, is 5-3,000 Hz.
One thing to note is amp outputs are going through a RLC filter, so the coil will see a sine wave that's similar to the audio tone generator that runs it, but as suggested, with a massive current capacity.
Look into something like Arta software for using a sound card to get speaker ( or shaker ) impedance vs frequency.
With a low impedance be careful how you hook it up to get the correct values.
Or use a simple signal generator / resistor / oscilloscope setup.
Having used a 90kVA Ling vibration system with tube amplifiers I can sympathize with your problem. Check with some of the vendors of vibration testing equipment (like Sentek Dynamics, Thermotron or Unholtz-Dickie). They have replacement amplifiers for exactly your application.
For those not understanding this, it is for shock and vibration testing of assemblies or products. The units being tested are bolted to a shaker. The shaker is like a field-coil driver on steroids. Shakers can be several feet in diameter and about as tall. Large amplifiers (or arrays of amplifiers) are used to drive the shaker. The larger the item being tested, the more amplifier power is required. One ton objects under test need about 100 KILOWATTS of amplifier, depending on the nature of the tests.
For those not understanding this, it is for shock and vibration testing of assemblies or products. The units being tested are bolted to a shaker. The shaker is like a field-coil driver on steroids. Shakers can be several feet in diameter and about as tall. Large amplifiers (or arrays of amplifiers) are used to drive the shaker. The larger the item being tested, the more amplifier power is required. One ton objects under test need about 100 KILOWATTS of amplifier, depending on the nature of the tests.
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