Older DC fractional HP motors
 

Many of such motors with wound fields required 90 volts for the field.
Why 90 volts and how was it derived?
thanks,
CP

Older DC fractional HP motors
 

On Sun, 2 Apr 2017 19:27:38 -0700, MOP CAP wrote:

Many of such motors with wound fields required 90 volts for the field.
Why 90 volts and how was it derived?
thanks,
CP
Some had field rheostats for speed control. As for the 90 volts,
likely the output voltage of a rectified line voltage using the
rectifier technology and line voltage of the time.

Older DC fractional HP motors
 

On Sun, 02 Apr 2017 22:42:36 -0400, clare wrote:

On Sun, 2 Apr 2017 19:27:38 -0700, MOP CAP wrote:

Many of such motors with wound fields required 90 volts for the field.
Why 90 volts and how was it derived?
thanks,
CP
Some had field rheostats for speed control. As for the 90 volts, likely
the output voltage of a rectified line voltage using the rectifier
technology and line voltage of the time.

90V probably became standard at some time in the dim past for reasons
that haven't applied since 1920, but has been carried forward because
it's a standard.

Just a guess, but you stumble across that sort of thing all the time.

--
Tim Wescott
Control systems, embedded software and circuit design
I'm looking for work! See my website if you're interested
http://www.wescottdesign.com

Older DC fractional HP motors
 

On Sun, 02 Apr 2017 22:42:36 -0400, clare wrote:
On Sun, 2 Apr 2017 19:27:38 -0700, MOP CAP wrote:

Many of such motors with wound fields required 90 volts for the field.
Why 90 volts and how was it derived?
thanks,
CP
Some had field rheostats for speed control. As for the 90 volts, likely
the output voltage of a rectified line voltage using the rectifier
technology and line voltage of the time.

Just as a guess, when you expect 120 VAC, you may only receive down to 70 from service for various reasons (due to back-up generators, peak/off-peak, voltage drops, over/under-voltages, surges, etc..), so you still want the thing to crank.

Older DC fractional HP motors
 

"Tim Wescott" wrote in message
...
On Sun, 02 Apr 2017 22:42:36 -0400, clare wrote:

On Sun, 2 Apr 2017 19:27:38 -0700, MOP CAP
wrote:

Many of such motors with wound fields required 90 volts for the
field.
Why 90 volts and how was it derived?
thanks,
CP
Some had field rheostats for speed control. As for the 90 volts,
likely
the output voltage of a rectified line voltage using the rectifier
technology and line voltage of the time.

90V probably became standard at some time in the dim past for
reasons
that haven't applied since 1920, but has been carried forward
because
it's a standard.

Just a guess, but you stumble across that sort of thing all the
time.

--
Tim Wescott
Control systems, embedded software and circuit design
I'm looking for work! See my website if you're interested
http://www.wescottdesign.com

This describes 90VDC motors as suitable for thyristor-regulated
rectified 120VAC.
http://www.leeson.com/Literature/pdf/b1600IEC.pdf

The mercury vapor tubes used as high power rectifiers before
comparable silicon diodes became available dropped around 15V.

-jsw

Older DC fractional HP motors
 

On Mon, 03 Apr 2017 07:18:05 -0400, Jim Wilkins wrote:

"Tim Wescott" wrote in message
...
On Sun, 02 Apr 2017 22:42:36 -0400, clare wrote:

On Sun, 2 Apr 2017 19:27:38 -0700, MOP CAP wrote:

Many of such motors with wound fields required 90 volts for the field.
Why 90 volts and how was it derived?
thanks,
CP
Some had field rheostats for speed control. As for the 90 volts,
likely the output voltage of a rectified line voltage using the
rectifier technology and line voltage of the time.

90V probably became standard at some time in the dim past for reasons
that haven't applied since 1920, but has been carried forward because
it's a standard.

Just a guess, but you stumble across that sort of thing all the time.

--
Tim Wescott Control systems, embedded software and circuit design I'm
looking for work! See my website if you're interested
http://www.wescottdesign.com

This describes 90VDC motors as suitable for thyristor-regulated
rectified 120VAC. http://www.leeson.com/Literature/pdf/b1600IEC.pdf

The mercury vapor tubes used as high power rectifiers before comparable
silicon diodes became available dropped around 15V.

-jsw

Hmm. That sounds about right if you used the field coil as the inductor
in a choke-input "filter".

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

I'm looking for work -- see my website!

Older DC fractional HP motors
 

On 2017-04-03, wrote:
On Sun, 2 Apr 2017 19:27:38 -0700, MOP CAP wrote:

Many of such motors with wound fields required 90 volts for the field.
Why 90 volts and how was it derived?
thanks,
CP
Some had field rheostats for speed control. As for the 90 volts,
likely the output voltage of a rectified line voltage using the
rectifier technology and line voltage of the time.

With modern rectifiers (silicon ones) that would work out to
about 64 VRMS. But vacuum tube rectifiers would have a lot more series
resistance, so that might work out with 110 VAC (the old line voltage,
which then jumped to 115 VAC, then 117 VAC, and now 120 VAC.) (And the
frequency used to be specified as Cycles-Per_Second (CPS) or '~' instead
of Hz. :-)

Also -- the rectifier was likely not used with filter
capacitors, so the RMS value of a half-wave rectified 110 VAC might be
pretty close to that.

Enjoy,
DoN.

--
Remove oil spill source from e-mail
Email: | (KV4PH) Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

Older DC fractional HP motors
 

Depends on the tube. I have vacuum tubes that pass 1000 amps to the
plate. About the size of your for-arm. Mil grade.

Then the real nasty ones for plating and welding - Ignatrons (sp) that
are mercury filled in a pool to splatter 10's of thousands of amps.

The big tubes I have are gas filled and were motor controls. Took two
on each motor and there were 3 motors to spin a very large triangle antenna.

Martin

On 4/3/2017 9:12 PM, DoN. Nichols wrote:
On 2017-04-03, wrote:
On Sun, 2 Apr 2017 19:27:38 -0700, MOP CAP wrote:

Many of such motors with wound fields required 90 volts for the field.
Why 90 volts and how was it derived?
thanks,
CP
Some had field rheostats for speed control. As for the 90 volts,
likely the output voltage of a rectified line voltage using the
rectifier technology and line voltage of the time.

With modern rectifiers (silicon ones) that would work out to
about 64 VRMS. But vacuum tube rectifiers would have a lot more series
resistance, so that might work out with 110 VAC (the old line voltage,
which then jumped to 115 VAC, then 117 VAC, and now 120 VAC.) (And the
frequency used to be specified as Cycles-Per_Second (CPS) or '~' instead
of Hz. :-)

Also -- the rectifier was likely not used with filter
capacitors, so the RMS value of a half-wave rectified 110 VAC might be
pretty close to that.

Enjoy,
DoN.

Older DC fractional HP motors
 

On Mon, 3 Apr 2017 07:18:05 -0400, "Jim Wilkins"
wrote:

"Tim Wescott" wrote in message
...
On Sun, 02 Apr 2017 22:42:36 -0400, clare wrote:

On Sun, 2 Apr 2017 19:27:38 -0700, MOP CAP
wrote:

Many of such motors with wound fields required 90 volts for the
field.
Why 90 volts and how was it derived?
thanks,
CP
Some had field rheostats for speed control. As for the 90 volts,
likely
the output voltage of a rectified line voltage using the rectifier
technology and line voltage of the time.

90V probably became standard at some time in the dim past for
reasons
that haven't applied since 1920, but has been carried forward
because
it's a standard.

Just a guess, but you stumble across that sort of thing all the
time.

--
Tim Wescott
Control systems, embedded software and circuit design
I'm looking for work! See my website if you're interested
http://www.wescottdesign.com

This describes 90VDC motors as suitable for thyristor-regulated
rectified 120VAC.
http://www.leeson.com/Literature/pdf/b1600IEC.pdf

The mercury vapor tubes used as high power rectifiers before
comparable silicon diodes became available dropped around 15V.

-jsw


Absolutely correct.

Gunner

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

Older DC fractional HP motors
 

On 4 Apr 2017 02:12:18 GMT, "DoN. Nichols"
wrote:

On 2017-04-03, wrote:
On Sun, 2 Apr 2017 19:27:38 -0700, MOP CAP wrote:

Many of such motors with wound fields required 90 volts for the field.
Why 90 volts and how was it derived?
thanks,
CP
Some had field rheostats for speed control. As for the 90 volts,
likely the output voltage of a rectified line voltage using the
rectifier technology and line voltage of the time.

With modern rectifiers (silicon ones) that would work out to
about 64 VRMS. But vacuum tube rectifiers would have a lot more series
resistance, so that might work out with 110 VAC (the old line voltage,
which then jumped to 115 VAC, then 117 VAC, and now 120 VAC.) (And the
frequency used to be specified as Cycles-Per_Second (CPS) or '~' instead
of Hz. :-)

Also -- the rectifier was likely not used with filter
capacitors, so the RMS value of a half-wave rectified 110 VAC might be
pretty close to that.

Voltages might have started out (in the Dark Ages?) at 110vac, but
they were 115v in my teens and are 120/240vac nowadays. It has been
that way for a long time.

I was thinking that rectification caused the drop to warrant building
90v and 180v DC motors.

--
That's the thing about needs. Sometimes, when you get them met,
you don't need them anymore. -- Michael Patrick King

Older DC fractional HP motors
 

Larry Jaques wrote:
On 4 Apr 2017 02:12:18 GMT, "DoN. Nichols"
wrote:

On 2017-04-03, wrote:
On Sun, 2 Apr 2017 19:27:38 -0700, MOP CAP wrote:

Many of such motors with wound fields required 90 volts for the field.
Why 90 volts and how was it derived?
thanks,
CP
Some had field rheostats for speed control. As for the 90 volts,
likely the output voltage of a rectified line voltage using the
rectifier technology and line voltage of the time.

With modern rectifiers (silicon ones) that would work out to
about 64 VRMS. But vacuum tube rectifiers would have a lot more series
resistance, so that might work out with 110 VAC (the old line voltage,
which then jumped to 115 VAC, then 117 VAC, and now 120 VAC.) (And the
frequency used to be specified as Cycles-Per_Second (CPS) or '~' instead
of Hz. :-)

Also -- the rectifier was likely not used with filter
capacitors, so the RMS value of a half-wave rectified 110 VAC might be
pretty close to that.

Voltages might have started out (in the Dark Ages?) at 110vac, but
they were 115v in my teens and are 120/240vac nowadays. It has been
that way for a long time.

I was thinking that rectification caused the drop to warrant building
90v and 180v DC motors.


120VAC*.707=84.84V Average, unfilterd DC


--
Never **** off an Engineer!

They don't get mad.

They don't get even.

They go for over unity! ;-)

Older DC fractional HP motors
 

On 2017-04-05, Michael A. Terrell wrote:
Larry Jaques wrote:
On 4 Apr 2017 02:12:18 GMT, "DoN. Nichols"
wrote:

[ ... ]

With modern rectifiers (silicon ones) that would work out to
about 64 VRMS. But vacuum tube rectifiers would have a lot more series
resistance, so that might work out with 110 VAC (the old line voltage,
which then jumped to 115 VAC, then 117 VAC, and now 120 VAC.) (And the
frequency used to be specified as Cycles-Per_Second (CPS) or '~' instead
of Hz. :-)

Also -- the rectifier was likely not used with filter
capacitors, so the RMS value of a half-wave rectified 110 VAC might be
pretty close to that.

Voltages might have started out (in the Dark Ages?) at 110vac, but
they were 115v in my teens and are 120/240vac nowadays. It has been
that way for a long time.

I was thinking that rectification caused the drop to warrant building
90v and 180v DC motors.


120VAC*.707=84.84V Average, unfilterd DC


That sounds wrong. The 0.707 multiplier is applied to the peak
voltage (170V) to get to the 120 VAC rating. Applying it again to the
result just feels wrong. :-)

However, if you are half-wave rectifying, with no filtration
capacitors, the RMS (Root-Mean-Square) value of that half cycle,
followed by another half-cycle of time, could be pretty close to the
90V rating for the field.

O.K. -- Looking in this site:

http://www.daycounter.com/Calculators/RMS-Calculator.phtml

gives this for a half-wave rectified value:


================================================== ====================
Half rectified wave Vrms= Vpk/2
================================================== ====================

so -- for the 170 V Peak, we get 85V RMS

so -- 90 V field allows for a surge of 127 VRMS ac -- so a worst-case
value.

Enjoy,
DoN.

--
Remove oil spill source from e-mail
Email: | (KV4PH) Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

Older DC fractional HP motors
 

On Tue, 4 Apr 2017 21:18:40 -0400, "Michael A. Terrell"
wrote:

Larry Jaques wrote:
On 4 Apr 2017 02:12:18 GMT, "DoN. Nichols"
wrote:

On 2017-04-03, wrote:
On Sun, 2 Apr 2017 19:27:38 -0700, MOP CAP wrote:

Many of such motors with wound fields required 90 volts for the field.
Why 90 volts and how was it derived?
thanks,
CP
Some had field rheostats for speed control. As for the 90 volts,
likely the output voltage of a rectified line voltage using the
rectifier technology and line voltage of the time.

With modern rectifiers (silicon ones) that would work out to
about 64 VRMS. But vacuum tube rectifiers would have a lot more series
resistance, so that might work out with 110 VAC (the old line voltage,
which then jumped to 115 VAC, then 117 VAC, and now 120 VAC.) (And the
frequency used to be specified as Cycles-Per_Second (CPS) or '~' instead
of Hz. :-)

Also -- the rectifier was likely not used with filter
capacitors, so the RMS value of a half-wave rectified 110 VAC might be
pretty close to that.

Voltages might have started out (in the Dark Ages?) at 110vac, but
they were 115v in my teens and are 120/240vac nowadays. It has been
that way for a long time.

I was thinking that rectification caused the drop to warrant building
90v and 180v DC motors.


120VAC*.707=84.84V Average, unfilterd DC

See? It's safe for a 90vdc motor. ;)

--
That's the thing about needs. Sometimes, when you get them met,
you don't need them anymore. -- Michael Patrick King

Older DC fractional HP motors
 

On Tue, 4 Apr 2017 21:18:40 -0400, "Michael A. Terrell"
wrote:

Larry Jaques wrote:
On 4 Apr 2017 02:12:18 GMT, "DoN. Nichols"
wrote:

On 2017-04-03, wrote:
On Sun, 2 Apr 2017 19:27:38 -0700, MOP CAP wrote:

Many of such motors with wound fields required 90 volts for the field.
Why 90 volts and how was it derived?
thanks,
CP
Some had field rheostats for speed control. As for the 90 volts,
likely the output voltage of a rectified line voltage using the
rectifier technology and line voltage of the time.

With modern rectifiers (silicon ones) that would work out to
about 64 VRMS. But vacuum tube rectifiers would have a lot more series
resistance, so that might work out with 110 VAC (the old line voltage,
which then jumped to 115 VAC, then 117 VAC, and now 120 VAC.) (And the
frequency used to be specified as Cycles-Per_Second (CPS) or '~' instead
of Hz. :-)

Also -- the rectifier was likely not used with filter
capacitors, so the RMS value of a half-wave rectified 110 VAC might be
pretty close to that.

Voltages might have started out (in the Dark Ages?) at 110vac, but
they were 115v in my teens and are 120/240vac nowadays. It has been
that way for a long time.

I was thinking that rectification caused the drop to warrant building
90v and 180v DC motors.


120VAC*.707=84.84V Average, unfilterd DC

Is that the constant for a gas rectifier tube, or a selenium stack?

Older DC fractional HP motors
 

On 2017-04-05, Gunner wrote:
On Tue, 4 Apr 2017 21:18:40 -0400, "Michael A. Terrell"
wrote:

Larry Jaques wrote:
On 4 Apr 2017 02:12:18 GMT, "DoN. Nichols"
wrote:

120VAC*.707=84.84V Average, unfilterd DC

Is that the constant for a gas rectifier tube, or a selenium stack?

Actually, it is the result of a pure rectifier -- no voltage
drop, so any real rectifier would have more drop. All of these are
larger drops than typical silicon rectifiers of today -- at least until
you get to seriously high voltages, which would have a number of silicon
junctions in series (at about 0.7V each) with resistors in parallel to
keep the reverse voltage evenly divided.

But in essence, any half-wave rectifier would produce voltages
safe for the motor. Stay clear of full-wave bridges, however, or
filter capacitors. :-)

Enjoy,
DoN.

--
Remove oil spill source from e-mail
Email: | (KV4PH) Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---