Regulator, regulators, power supply, regulator rectifiers.

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.