[ARC5] Fwd: Smart People: 60Hz Transformers Faster?

[Brian]

Bear in mind that in China, labour is very cheap, and if it gets killed in 
the game of progress, the producer seldom gets called for slave labour or 
inhumane working conditions. Look at the injunction on connecting the 4th 
wire.
I noticed that although 0.01 Hz speed resolution is claimed, there is no 
corroboration of that, such as an independent test certificate. And there is 
no claim about wave-form or its likely effect on a motor.

And this is just a motor speed control device. You still need to buy the 
mounting board, the 3-phase motor, the generator and the coupling - and 
possibly the tachometer for speed control feedback. What is the overall 
efficiency going to be like? The DM-32 had a FL efficiency of under 50%. Or 
perhaps Tom had in mind that the output would be fed to a 3-phase 
transformer - they're readily available, aren't they? A high-power audio 
amplifier running Class AB may reach 75% and may even be smaller than a 
motor-generator set. A Class D audio amplifier will have even higher 
efficiency and be even smaller.

As an engineer, I have dealt with Chinese manufacturers before. They work to 
quite different standards from the west and get all shirty when you call 
them for it. On one job, a car-lifting device, the safety factor on the wire 
ropes was around 0.3. When I called the manufacturer's designer on this, he 
refused to pay for my engineering assessment. I am not basing my judgement 
on just this one example - there have been others. Here is another for 
instance: at this time of the year, Australia gets inundated by cheap 
Chinese toys that fall to pieces 0.16 seconds after the recipient gets to 
it. And the little coloured pieces are very attractive for getting your 
child taken to hospital to have them removed. Sort of reminds me of labour 
hire and care practices of Morgan and Rockefeller in the 19th century.

73 de Brian, VK2GCE.

On Tuesday, November 24, 2015 2:22 PM, you said:

Hello All,

Anybody out there tried to use a variable frequency motor drive to do
this?  I was looking at ebay 191553950271 that might do it.  It is rated
at 1.5kW and goes up to 1000Hz.
I know the output is not a perfect sign wave but I am not sure if that
matters for this application.

Tom Bryan
N3AJA