Building a micro generator, I need to account for the pulsing DC after the 3 phase diode bridge

I wound my own motor, and tested it to be about 300 RPM per volt, and if my noob math is right, it should be able to handle about 1600 watts with a ~40 volt supply without burning my nice but thinly insulated wire.

My idea now is to drive this motor with an engine of some kind to get it to turn a little more than 12000 RPM, run the 3 phases through a powerful 1600v 150a rated diode bridge, and hook a capacitor on the other end.

The problem is, I borrowed a friend's oscilloscope and found that when I turn it at about 1,000RPM with a drill, I am getting HUGE voltage spikes. There's obviously little to no load, but i'm getting 4-500v spikes, maybe even up to 1kv. They're very very short spikes.

I get the picture that these will disappear with a load on the motor, but I want to ensure the several thousand hertz DC pulses I am getting at the other end are being somewhat dampened by a capacitor. Is there some math I can do to determine what voltage rating and how many farads/microfarads I need to balance the pulses out? I'm worried about getting a cap rated for 500v and it being too much, but I'm also worried about it blowing the eff up when I actually start putting power through it. I've intentionally blown up tiny electrolytic caps and they are basically bullets. Don't really want to find out what a hand grenade sized one will do.

If there's no way to bridge the super high frequency pulses in a small form factor, I suppose I can just wind the motor to a lower v/rpm, but either way, I want to do it safely.

My end goal is to get 1,000 watts out of it, although 1600 would be outstanding. I doubt the system is going to be more than 10% efficient, but we'll see.

As a side note, I plan on shielding the whole thing with brass mesh to keep EMI down, as I imagine it will produce quite a lot.