I am tasked with the job to either find or commision the custom design or design for myself... a regulator circuit for a brushless 5KW 3PH AC burshless generator that gets it's output rectified to produce a 340VDC @ 15 amps power source.
This is my first expereince with a generator.
Coming from a background in linear and switchmode power supplies, the first thing I notice is how slow a generator responds to changes in excitation coil current; in particular to the excitation level dropping. Also I note how awfully large the output ripple with a rich splash of harmonics relating to the number of poles in the output and exciter windings.
The big issue I am facing is load dump transient response. The generator takes several hundreds of milliseconds to reduce it's output voltage after a
15 amp load is removed from the 340VDC rectified output. During this time the generator output voltage is more than double!Odd I find because the excitation coil is shut off by the regulator circuit alomst instantly and I can see it decays to nothing in just under 100ms.
I notice the generator output can handle going from no load to full 15 amp load in less than 100ms and this way it has a fast transient response. My output L/C filter cleans things up nicely. But going from full load 15 amps to no load 0 amps is turning out to be a nightmare!
I am told the rotating excitation coil inside has some diodes on it, and that this is a typical construction of a brushless generator. The rotating excitation field coil freewheels it's current through these diodes and the resulting field decay rate can be surprisingly slow.
What can be done to speed up a brushless generator's load dump recovery time? What type of output over-voltage protection schemes are typically used in a generator based DC power supply? I can't have downstream electronics modules connecting to my output getting blown-up with voltage rises of up to
+100% which last for 1/2 second or more! Yet to clamp or limit or otherwise switching regulate or filter 5KW of power for almost 1/2 second long seems like an expensive and tricky prospect?Looking for pointers to off-the-shelf equipment suppliers???
Custom design expertise resources (companies and consultants)???
Suggested circuit topology and critical components one might use along with their ratings???
Any layout and assembly issues which would promote reliabilty and avoid EMI as much as possible???
This will be required for a rugged mobile application with wide range temperature specification and high shock/vibration levels. Low cost is the primary driving factor. Weight and compactness are not that much of an issue.
Suggestions anyone?
Terry Moreau
snipped-for-privacy@direct.ca