CAD-CAM-EDM-DRO@groups.io

Jon Elson

"Ian W. Wright" wrote:

From: "Ian W. Wright" <Ian@...>

Sorry to seem so dim but what, pray, is a mag amp?

The trick Bridgeport uses (pretty tricky, but not original) is to use a mag
amp on the AC input to the rectifier.Sorry, old technology.  Mag amp is short for a magnetic amplifier.
This goes back to WW-II, and certainly Korea.
A way of getting a lot of gain without much energy loss is to use a winding
of many turns of fine wire to drive an inductor into and out of saturation.
When the inductor is saturated, AC current passes through a winding
of a modest number of turns of heavy wire fairly easily.  When the control
winding does not saturate the inductor, then the inductance blocks the
power flow through the power winding.

Jon

"Ian W. Wright" <[email protected]

#566

Thanks Jon but let me just get it clear. Are you saying that if you put,
say, the high voltage winding of a mains transformer in series with the
low voltage motor, it will boost its starting torque?

Ian

Jon Elson wrote:

Show quoted text

From: Jon Elson <jmelson@...>

"Ian W. Wright" wrote:

From: "Ian W. Wright" <Ian@...>

Sorry to seem so dim but what, pray, is a mag amp?

The trick Bridgeport uses (pretty tricky, but not original) is to use a mag
amp on the AC input to the rectifier.Sorry, old technology.  Mag amp is short for a magnetic amplifier.
This goes back to WW-II, and certainly Korea.
A way of getting a lot of gain without much energy loss is to use a winding
of many turns of fine wire to drive an inductor into and out of saturation.
When the inductor is saturated, AC current passes through a winding
of a modest number of turns of heavy wire fairly easily.  When the control
winding does not saturate the inductor, then the inductance blocks the
power flow through the power winding.

Jon

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Best wishes

Ian

-- 

Ian W. Wright LBHI
Sheffield Branch Chairman of the British Horological Institute. 
Bandmaster and Euphonium player of the Hathersage Brass Band. UK.
See our homepage at:-  or
 or
 

'Music is the filling of regular time intervals with harmonious
oscillations.'

Jon Elson

#567

"Ian W. Wright" wrote:

From: "Ian W. Wright" <Ian@...>

Thanks Jon but let me just get it clear. Are you saying that if you put,
say, the high voltage winding of a mains transformer in series with the
low voltage motor, it will boost its starting torque?No.  What is similar to the low voltage winding of a mains transformer
would be put in series with the AC output of the real mains transformer,
before the rectifiers.  This would lower the current flowing through the
rectifier, and bring down the DC voltage at the capacitors after the
rectifier.

So, the mag amp goes into the power supply, and is not connected
to the motor.  Also, a mains transformer would likely make a poor
mag amp.  Special magnetic laminations much different from ordinary
transformer iron would be used.  Also, the control winding would
be wound with LOTS of turns of fine wire, to minimize power
demand to saturate the iron.

I hope this helps clear it up.  Anyway, there are much better ways
to do this, today.  A chopper-type stepper drive is cheaper,
more efficient, probably more reliable, more responsive, a
LOT smaller and lighter, etc.

Jon

"Ian W. Wright" <[email protected]

#595

Thanks Jon.

Ian

Jon Elson wrote:

No.  What is similar to the low voltage winding of a mains transformer
would be put in series with the AC output of the real mains transformer,Best wishes

Ian

-- 

Ian W. Wright LBHI
Sheffield Branch Chairman of the British Horological Institute. 
Bandmaster and Euphonium player of the Hathersage Brass Band. UK.
See our homepage at:-  or
 or
 

'Music is the filling of regular time intervals with harmonious
oscillations.'

Mike Chaney <[email protected]

#591

Jon Elson wrote:

Sorry, old technology.  Mag amp is short for a magnetic amplifier.
This goes back to WW-II, and certainly Korea.
A way of getting a lot of gain without much energy loss is to use a winding
of many turns of fine wire to drive an inductor into and out of saturation.
When the inductor is saturated, AC current passes through a winding
of a modest number of turns of heavy wire fairly easily.  When the control
winding does not saturate the inductor, then the inductance blocks the
power flow through the power winding.
Ah!  You mean a "saturable reactor".  These were once the cutting edge
technology for stage lighting dimmers - until someone invented the
thyristor.

Mike

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Term: Mag Amp