🚀 go-pugleaf

In article <1775@marlin.NOSC.MIL> bryan@marlin.NOSC.MIL (Dale Bryan) writes:
>does anyone know of an acoustically quiet dc brushless motor controller (120V)?
>we are using 3/4 hp dc brushless motors with buil in motor controllers to
>drive thrusters on an underwater vehicle.  the problem is that the motor 
>controllers pwm frequency and its harmonics is radiating sound into the water.
>this sound is interferring with acoustic sensors aboard the vehicle.
>thanks in advance.

If you don't mind the extra heat and lower effeciency, you could just use a
straight DC amplifier.  Fortunatly, because you would be underwater, you could
design heat sinks that would make use of the water to give you lots of heat
dissipation that you would probably need at that kind of power.

If you have/can make a bipolar power supply (easy if you have AC and the right
transformer), then you can build a simple T-type (two transistor) amplifier
for each motor.  Since I'm sure that other people here know what a T-type
amplifier is, and they probably have the actual circuit theory down better
than I do, I'll let someone else draw you a schematic.  However, it's quite a
simple design, and easy to build (I've done it). 

If you only have a single voltage power supply, you can build an H-type
amplifier, but they are more complicated and expensive.

Either way (H or T), they ought to provide you with a very quiet power system.

+---------< Eric A. Rasmussen - Mr. Neat-O (tm) >---------+ +< Email Address >+
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