Power supply for 115v, 400Hz, 3 phase motor

Other Hardware Motors, Mechanics, Power and CNC
1

Hello,

I've managed to acquire some antique avionics kit - a really nicely built gyro in an autopilot module. I've poked around it a little bit and to my dismay found that the motor driving the gyro is a 3 phase 115 V 400 Hz AC unit (this is a standard for aircraft electronics). My problem is finding/building a cheap power supply that could drive this and I really don't know enough about AC.

Now there are variable frequency drives available, but most of these are for industrial equipment or aviation use and are far too expensive for me. Is there a cheap/DIY option out there? What if I try to hook up standard 220V 50Hz from a household socket?

2

The gyro motor really does require 400 Hz AC and if you connect it to 50 or 60 Hz AC, it will likely be destroyed. People have built low power, three phase 400 Hz power supplies, google "diy 3 phase 400 hz power supply" for more info.

3

I did some googling before posting this and there seem to be two main approaches.

  1. Use a correctly matched motor-generator set and perhaps some mechanical gearing.

  2. Use switched DC power and a transformer. Something like Question 30 here. But that's only singe phase.

The second options seems easier/cheaper, but how would I do this 3 phase? Use 6 PWM outputs and 3 transformers?

4

For a plain induction motor a frequency that is too low is likely to cause far too
much current to flow (current is limited largely by the induction of the windings
for such an induction motor, and 400 / 50 is a factor of 8, too large to risk).

It will also spin too slowly to be of use. Being lucky finding a secondhand VFD seems
the most likely option...

5

Have you seen this kit? http://www.kenneke.com/avionics.html
I'll bet it is not pure sine wave but it would probably work fine to power a gyro motor.