The K1WHS Light & Power Company

In September 2007, The G.O.D. suffered a serious mechanical failure in the engine, and was replaced by a new diesel generator. For the time being it is being called the Little G.O.D. You can read all about it here. The Little G.O.D. The new machine is mounted on a cement pad rather than a trailer. We are hoping that it will provide great AC power for future VHF contests. We were sure spoiled by the previous 30 KW 3 phase machine.

THE GENERATOR-O-DEATH! The first year in use, Winter 2001/2002

How to power all this equipment when the nearest power line is 1/2 mile away? With a station that is far from commercial power lines, homemade power is the only way to go. If you want good electric power to run fairly high power transmitters, you really need a good generator. Diesel engines are perfect choices for such applications. Constant speed over long periods of time are diesel strongpoints. Such units typically run at 1800 rpm or less, and will provide continuous power over long periods of time. Most gasoline generators in home use run at 3600 rpm, and are not made for continuous service. A large commercial generator will have speed regulation and voltage regulation. Our power source has an electronic speed regulator that senses speed with a magnetic pickup sensor reading the gear teeth on the flywheel. A 3000Hz pickoff signal is used to regulate the speed of the engine by adjusting the throttle linkage through an electronic actuator. As the 3000 Hz frequency varies with engine speed, an error signal is developed to bring the engine back to it's original speed. A voltage regulator maintains the voltage by controlling the magnetic field in the brushless generator. Most large generators have an excitation winding (actually a DC generator) that provides the charging current to maintain the flux level in the high powered AC alternator at a constant level. If the voltage sags under load, the regulator increases the voltage in the excitation winding to bring the alternator output voltage back up to normal levels. Because of the delay, a rapidly varying load (such as SSB or CW transmitters) can make voltage regulation difficult. Large diesels typically have quite good regulation due to sophisticated regulators as well as the "flywheel effect" from a larger engine with a substantial (heavy) flywheel to help smooth out peak current surges.

The PU-708 awaiting repair and modification in April of 2001 (Yeah that's a lot of snow for mid April!)

A 2 cylinder Detroit Diesel engine provided up to 30 KW of 120/208 vac 3 phase power, and comes with a huge flywheel to help even out the voltage on voice peaks. This unit varies about 1/2 volt on the 120 volt line no matter how many transmitters are going. Since this picture was taken, we have constructed a generator shed to protect the machine from the elements and cut down on engine noise. This generator was picked up "real cheap" because it was not in working shape. It is a Marine Corps PU-708/G 30 kw 120/208 3 phase design left over from the Vietnam War. Actually, the engine ran, and the generator windings made electrons, but the speed regulator was shot. It had 79 hours of use after a depot rebuild by the Marine Corps in 1977. Apparently it had sat around for many years between 1978 and 2000 when I purchased it. Someone with a blowtorch and boxing gloves had tried to repair it before I got the generator. It sat out in this field for the winter of 2001. We (K1DY and K1WHS) had to shovel about four feet of snow away from it to try to repair it. The end result is that I am now pretty knowledgable about diesel generators! After much investigation and a steep learning curve, I deduced that the only problem with the speed regulator was that a speed calibration pot had developed an intermittent dirty spot on the wirewound wiper surface and had let go. Much damage to other parts of the circuit had been done by a previous owner. Once those problems were fixed,I had a great system that seemed to work quite well. In dealing with the manufacturer, they advised that I should update the unit as more modern and accurate systems were available over the fuel pressure actuator system I had just got working. I guess back in 1968, solid state electronics were not sufficiently developed to drive a diesel fuel actuator directly. Instead they utilized a small electric signal to direct the 60-100 pounds of diesel fuel pressure to move the actuator arm. I took their advice and upgraded the engine controller to a modern, all electric governor, and threw out the old fuel oil pressure actuated system. It was a very good move, as now, the unit will just sit there and purr along at 60.1 Hz no matter how many rigs and air conditioners we run. Did I mention that there is about 8.5 Kw of electric baseboard heating in the shacks, and another 6 kw of baseboard heating in the generator shed? Diesels like to have a load on them or they are unhappy. This generator runs so reliably, with constant rpms, that I can actually use a 115 vac electric wall clock and keep pretty good time over several days of use!! The entire generator has now been housed in a shed to keep the weather away and allow for some quieter operation. The engine is a Detroit 2-71 2 cycle engine with a humongous blower on it for air supply and scavenging of the cylinders. Before building the shed, it was plain LOUD. After the shed was built it is still loud, but, at least it does not cause hearing damage.

The protective circuitry in this generator is quite extensive. Some of it was, unfortunately, missing when I took ownership of this machine. No doubt a result of the previous owner trying to make the unit work. A crucial missing link was the overspeed shutdown circuit. Where it had originally resided, was just an empty PC board slot! A 2 cycle diesel engine, while very reliable, has a nasty habit of being able to power itself on engine oil. Should a serious malfunction occur such as broken piston rings, or a cracked block, it would be possible for the engine to keep running using motor oil as the "fuel", regardless of any throttle settings. The end result is a possible runaway engine. This Detroit engine is fitted with an air shutoff solenoid to remove the air supply to the cylinders in the event of engine runaway. In addition, if the engine should lose regulation and increase (or decrease) speed by a large amount, an electronic circuit will sense the engine speed and shut down the system automatically. The high speed shutdown circuit had to be designed from scratch. I constructed an active IC bandpass filter to monitor the 3000 Hz speed signal off the flywheel teeth. If the frequency went out of range, an error voltage would activate relays to shut down the system. It works very well and provides peace of mind during operation. In addition, there is a fuel pressure shutdown relay, a high engine temperature alarm and relay, a low fuel level warning and shutdown, and a low oil pressure alarm and relay. Lights on the control panel warn you when things are getting close to the safety limits and before shutdown occurs.

PROTECTION CIRCUITS

Note the empty PC card holder on the extreme right. This was the missing high speed shutdown circuit. I had to make a new circuit board from scratch! The finished project used the same card rails, and works quite well. If the engine hits about 2000 RPM it will shut off! Other circuit cards provide voltage regulation, drive voltage for the cycle/Hertz metering, oil pressure and temperature shutdown circuits, and AC overload circuits.

PU-708 INSTRUMENT PANEL

This is a photo of the main instrument panel for the PU-708. Upon close inspection, it can be seen that there are two sets of almost everything as the set has the option of being remotely controlled through a large multi pin MS connector visible on the lower right. Many of the controls on the left panel are duplicated on the right panel as welI. I have not implemented any of the remote monitoring capabilities. My only remote sensor located in the operating buildings is a frequency counter monitoring the 60 Hz mains frequency, and an AC voltmeter.

The control panel has gauges for fuel level, oil pressure, engine coolant temperature, 24 volt battery charging current, running hours, and switch selectable voltage and current for each of the three generator phases. In addition there are voltage and frequency (speed) adjust controls, protection bypass switch, emergency shutdown switch, and panel lights to warn of low fuel, high temperature, low oil pressure, and electrical overload conditions. There is even an option to engage a large alarm bell should any of the warning lights come on. The metering includes two voltmeters, an ammeter, and an expanded frequency meter, (far right) that reads 58-64 Hz. That is used for setting the engine speed, controlled by the large knob just below the meter. The red switch cover on the right, is a protection bypass switch. It must be activated when first starting the engine, otherwise, the engine will not start (no oil pressure, low engine speed etc). For cold weather starts, the engine is equipped with an ether cylinder that looks very similar to a propane torch cylinder. A special knob dispenses a shot of ether into the air intake to fire the cylinders when the temperature goes below about 30-32 degrees.At such low temperatures, the diesel fuel does not properly ignite, and the engine needs some help. I have tried the ether down to about 0 degrees farenheit with good results. After the cylinders get warm from a few explosions, it will run with diesel fuel just fine. The bad news is that ether is hard on the engine, but the Detroit 2-71 is a very rugged engine and can take the abuse where others cannot.

 

This generator is a 3 phase unit that will produce 208 vac and 120 vac with a total output of 30 kw. Being a military unit, it has considerable overload capability. I have yet to fully load any of the phases. For a few years, we ran the whole station on just one of the phases with great results. I estimated we pulled about 16 KW from one phase, and it was nowhere near full capability. The engine is capable of developing enough energy for about 45 KW. Lately we have invested in a 3 phase panel and run all three phases to the shack. It is easy to run each band PA power supply on a separate phase. The 222 and 432 stations are doubled up on one phase, while 50 and 144 have their own phase. It is also important to have all the low power equipment running on the same phase to avoid ground loop problems between phases. As mentioned earlier, this machine was built for the US Marine Corps, and is equipped with all sorts of nice features. One of them is an auxilliary fuel tank to augment the internal 20 gallon tank. The internal tank has fuel switches built into the tank that will turn on a pair of 24 vdc fuel pumps and pump fuel into the tank as the internal tank gets low. When the tank is full, another fuel switch turns off the pumps. We have fitted a second 55 gallon tank that feeds the internal tank, so we have a total of about 75 gallons available for use. This translates to about 44 hours of non stop fun! An interesting sidenote... When the genset was rebuilt down in Georgia, in 1977, some swiftie managed to wire up one of the fuel tank switches backwards, so that the pumps only came on when the tank was full. (D'oh!!) There was a backup shutdown system that prevented a fuel overflow, but it was confusing to troubleshoot, as you assume that the unit was wired properly in the first place!! It was impossible to rewire the internal switch as it is sealed and explosion proof, being located down inside the fuel tank, so I rigged up a transistor switch to operate 180 degrees out of phase! Problem solved!!! Now, for a contest weekend, we fill the two tanks beforehand, and let it run all by itself. As it needs more fuel, it pumps fuel from one tank into the other, automatically.

The newly constructed generator shed, 2002

The generator shed shown here really cuts down on the noise from the 2-71 engine. The high speed air intake blower really whines and is deafening if you stand near it. The shed was a worthwhile improvement. It also keeps the weather off of the generaor housing as well. The shed is located about 150 feet away from the two shack buildings. Three phase power is fed to the buildings with large aluminum entrance cable.

In 2007, during the September VHF Contest, we experienced a serious failure with the 30 KW military generator. On Sunday morning of the contest, we were greeted by a severe loss of power and thick black smoke in the exhaust. We shut it down early in the evening, when we determined that the engine was making unusual mechanical noises. The problem was found to be a failure of the air blower assembly, and metal dust from impellor blades was forced into the cylinders. It was quite a loss, and it took quite awhile to dertermine the exstent of destructiion, and then come up with a plan to secure power for upcoming contests. It was decided to replace the G.O.D. (Generator-O-Death!) with a modern but somewhat smaller unit. We chose a 20 KW electronic speed controlled Cummins diesel power plant with a 208 volt 3 phase generator end. The unit we picked was skid mounted in a soundproof enclosure complete with a 65 gallon fuel tank built in to the enclosure. Some considerable re wiring was needed as the newer unit did not have all the bells and whistles available on the old military unit. The wiring was completed in the winter of 2007/2008 and the new genset was ready for use in the Springtime. Working during the winter months here is problematic as the site is not accessible during periods of heavy snow cover. We had excessive amounts of snow all winter! Our first use of the new generator met with disaster in the June Contest. It rapidly overheated and promptly shut down! You can cointinue the saga here.

 

PICTURE

 

OUR ORIGINAL POWER SOURCE 1985-2001

The old power unit in use from 1985 thru 2001 was a gasoline powered International Harvester U-2 engine driving a 9.6 kw generator complete with a DC excitation generator driving a slip ring type alternator. I estimate it was built around the late 40's or early 50's. I had to replace the old voltage regulator with a modern solid state unit, and completely tore apart the outer portions of the engine for a thorough cleaning and lubricating of the mechanical governor. The first photo shows the unit being stripped down and cleaned up in my garage back in 1985. I had purchased the generator from a local generator outfit as a "Mr. Fixit" Special. I basically got a quick course in what makes a generator work. Setting up the voltage regulator and cleaning and adjusting the governor, carburetor, and magneto were all good training for the later diesel outfit that had a whole new set of problems!! That original gasoline powered unit was spec'd at 5% speed regulation with the mechanical governor, which was very inferior to what we have today. In addition, while parts were available, we would run through distributer caps and plugs on a yearly basis. With the engine out in cold weather, it took a beating. The maintenance level was very high with our old unit. Keeping the engine running on all four cylinders was difficult. In addition, the magneto had so much voltage that the sparkplugs interfered all the way up to 903 MHz!! I had to double shield the spark plug wires, and build a copper box around the magneto, to eliminate RFI on the VHF bands. The extra shielding made working on the unit much more difficulot, as most of the work involved plugs and distributer problems and they were all shielded! That engine was a standard on all International Harvester Super C tractors, and developed about 18-20 horsepower at full load and max rpms. In running an 1800 RPM generator, it developed less power. The generator portion would deliver about 12 KW of power, and then the engine would start to stall. It would not handle full 1500 watt stations on the four lower VHF bands very well as a result. We ended up running an AM-6155 amp on 222, and KWs on the other bands. The lights tended to blink a little.

 

 

PICTURE

 

We ended up putting the generator in a small shed to keep it dry. You can see the generator inside the shed in this picture. You can also see the tin foil wrapped around the spark plug wires to reduce rfi. This thing really needed a lot of ignition suppression to make it quiet. That is another reason to run a diesel engine! The final reason to run a diesel engine is so that the 4- wheeler kids on their ATV's will not siphon the gas out of your fuel tank the day before a VHF contest! (Yes it happened!) We ran the old "gasser from 1985 until 2001, so I cannot complain much. It really was a workhorse. The main problem was that our electricity requirements outstripped its capacity. It could not run four 1.5 KW stations let alone the air conditioning and assorted coffee pots, baseboard heat etc. The old "gal" is still happily making electricity as backup power at a local woodworking shop here in town.