Most things are designed with a specific use in
mind and regulator rectifiers used for converting alternating current (AC)
to direct current (DC) at a desired voltage level are no exception.
Alternators, weather they are Permanent Magnet (type used in two cycle and
some four stroke engines) or belt and gear driven, with a variable field
(used in the general aviation and automotive market) produce AC.
The Voltage level and frequency of that AC is
directly proportional to the speed, or RPMs of the engine. That AC must be
converted to DC and then regulated to a safe and useable level to power
various electrical devices. That level should be between 13.2 and 14.3
volts. This voltage level will safely charge a lead acid battery. A
properly designed electrical system should have a battery to stabilize the
system. Under certain circumstances the battery can be left out like in an
ultralight aircraft where the weight of a battery becomes a more important
factor.
However, doing so one should be mindful of
several hazards. Voltage spikes, ripple (noise), higher than normal
voltage levels, and worst of all a failed regulator that shorts through
and fries all the devices (Radios, GPS, lights, etc.) down stream. The
latter may not even be prevented by having a battery installed. Also, a
fuse will not protect from over voltages. Fuses work on Amps not
volts.
Having said all that, let us now
talk about the regulator rectifiers available to the Ultralight and
Experimental aircraft market. The SHUNT type, there are several brands on
the market, you know the ones priced around $60. Their operation is fairly
simple. Using an SCR (switch) controlled by a Zener diode (voltage level
sensor) they short out (shunt) the incoming AC to control the voltage
level (regulating before rectifying, this is why the AC as well as the DC
is lowered to 14 volts).
Then this voltage is sent through a full wave bridge
(four diodes) which convert it to DC. Then on to a capacitor to filter out
most of the ripple. One that is widely used doesn't have the capacitor so
you must add one externally. A battery could be considered a very large
capacitor. Shunt regulators are encased in aluminum blocks to help
dissipate the heat, some even have cooling fans. They burn up a lot of
power (Watts) by their short circuit operation which creates that heat. A
Rotax 503 or 582 at 6300 RPMs will put out as much as 90 to 100 volts.
Now, with this type regulator that level is shorted
down to 14 volts. All of this means unnecessary wasted horsepower from
your engine. On the plus side, SHUNT regulators are relativity inexpensive
and produce larger current flow (Amps).
If you need a lot of electrical power all of the time I would
suggest a Shunt type regulator connected to a battery of at least 17 Amp.
hour capacity. Nothing smaller and NEVER without a battery. To do so is
playing Russian Roulette with your expensive equipment. One more thing I
would like to mention on shunts. There is a very inexpensive ($25) 2" X 2"
square block with 2 yellow, 1 red, and 1 black wire that is being sold as
a shunt regulator that works if it has a 1 Amp load. This is true only if
used on the 30 watt (green) coil of the older point equipped
engines.
If you are not using an electric
starter and high amperage consumers like landing lights you may want to
read about a SWITCHING type regulated power supply built by Kuntzleman
Electronics. The Precision Power
Supply uses a full wave bridge to change
the incoming AC to DC. This DC is then pre filtered and sent to a
precision switching regulator that is controlled by an integrated circuit.
Through sampling the output, this IC controls the
regulator for an accurate level of 13.8 volts +/- 1% and current limiting
to 3 Amps. A quality monitoring circuit takes a look and if all is okay
the power is filtered again and sent on to be used. If the monitor sees
anything that isn't okay (higher than safe voltage levels even spikes) it
shuts down the system (crowbar) within microseconds, long before any
damage is done to your expensive radios.
So, you can see this is not just a regulator rectifier.
It is a regulator power supply producing pure filtered 13.8 volts DC,
regardless of load, up to its 3 amp limit. It is over voltage protected
and short circuit proof. If a short should occur somewhere in your
electrical system the regulator will simply turn down the voltage until
the short circuit is removed. This supply will not put an excess load on
the engine. It only produces what your equipment is asking for, nothing
extra only to be wasted as heat. The PPS can be used with or without a
battery on any single phase alternator, no matter how high the Wattage
rating.
Your electronic equipment as well as your engine is expensive
and should have a long life if taken care of and fed properly. You
wouldn't think of using a poor grade of gas or oil in your engine. So why
feed your electronics a poor grade of power? |
Precision Power Supply
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When connected to the lighting coil
of the engine it will provide 12 volts of pure noise free safe DC power @
3 Amps. This power is used to operate radios, including CD, navigation
equipment such as GPS, DC powered gauges, etc.
The PPS is a pass
type-switching regulator, so it will not interfere with tach, strobes or
any other AC equipment. It can be used with or without a battery in the
system. When used with a small to medium sized battery it will safely keep
that battery charged.
It also features a watch dog circuit to carefully monitor
it's DC output. Thus eliminating the danger of voltage surges and noise
spikes damaging your expensive equipment. The 4 1/2 x 3 1/2 inch unit
weighs only 10 oz.. |
Price $128.00 U.S. |
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