Tip & How-To about Electrical Supplies
There are 4 requirements that have to be met before a generator is able to produce power. Due to number of questions that have been asked, a Coleman PowerMate 1500-1850 with a Briggs and Stratton Engine will be used here.
1) The Engine has to be turning at correct speed
2) Field Winding (Rotor) on the alternator must be energized
3) AC Winding (Stator) must create a voltage in presence of magnetic field
4) Output passes through Safety Devices before it reaches an outlet.
This Tip will cover Engine Speed and Governor Control.
Sounds simple, but it actually goes beyond just turning. Most consumer generators are designed for an engine that turns 3600RPM for 60Hz operation. For every 600 RPM, the frequency changes by 1 Hz. Normal frequency range on a generator is about 63 (at no load) to 57 (Full Load). At half load, you should be pretty close to 60 Hz. Some generators will turn at 1800 RPM, and usually have two or more cylinders. Each 1Hz deviation is a 300 RPM change in engine speed
If you find that your engine is not turning as fast as it should, or is turning too fast, you can adjust its speed using the governor. Be careful in this area though! If you are adjusting faster, and you make too much an adjustment, the engine may over speed (red line) and be damaged. Always be ready to shut down the engine in case something goes wrong.
General Instructions on How to Adjust Speed:
It will almost be required that you have a digital multimeter that is capable of measuring frequency. You can use a AC powered clock, and compare the minute intervals with another clock, but the adjustment process will take a few hours.
Start your generator, let it run for a few minutes to warm up. Place your meter leads into the outlets, and record the frequency. This will be your No Load Frequency prior to any adjustments. Also record the voltage.
Note that depending on your meter, your voltage will likely read about 132 volts AC. If your meter is of the dollar store variety, the voltage may be reading higher (170) due to noise being present in the waveform. Don't worry about this - yet.
Now that the engine is warmed up, and your meter is indicating that the frequency is less than or higher than 63Hz, it is time to adjust the governor. Each engine will have its own method, you may have to find a owner's manual or service manual.
Start by removing any access panels that you need in order to reach the governor assembly. This will be the arm that is attached to the throttle on the carburetor via springs and rods. Look carefully near the base of the governor arm, and you will see a spring that is attached to it, and the other end is attached to a tab. The purpose of this spring is to put tension onto the governor, as well as to allow adjustment. Inverter based generators will usually have an electronic governor. The throttle is actuated by a small servo motor which is driven by the inverter / controller. These types of governors are typically not adjustable beyond replacing mechanical linkage that is worn.
Using a pair of needle nose pliers, bend the tab slightly one direction or the other (toward governor, or away from governor). Note the change in frequency. The target here, without a load, is going to be 63Hz. Once you hit this target (frequency average is 63), take a look at the voltage. It should be near 132 volts AC. If it is much higher, then lower the voltage by bending the tab slightly. Be aware that this will also lower the frequency as well.
Now that the unloaded frequency is set, connect a load that is approximate half of the generator continuous rating. For an 1800 watt generator, the continuous load is 1500 watts. Half would be 750 watts. A couple of Halogen lights will work, as well a space heater that is set on Low. Your frequency should be very close to 60Hz now. Voltage will likely be around 125 volts. Adjust the governor very slightly to reach these numbers. Your half load frequency is now set.
If you are using a space heater for a load, turn it on (1500 watts), and note the frequency reading. Also note the voltage rating as well. Frequency will likely have dropped down to about 57 or 58. This is normal. Voltage should be down around 110 to 115. Don't make any adjustments as most generators are due not carry full loads for extended amounts of time.
Turn the heater back to low or fan only, and let it cool for a few minutes before turning it off. Unplug the heater, and check the frequency and voltage without a load being on the generator. Again, frequency with no load should be about 63Hz, voltage about 132. A little bit of difference is acceptable here. And now you are done.
If you are not able to obtain the numbers mentioned, then there are other issues going on. Especially if voltage is out of range. See other Tips.
If you intend to use the generator primarily with a certain load (heater, well pump, charger, etc) you can optimize performance of that load by setting the generator frequency with that load, and only that load connected. Just keep in mind that when you add additional loads, your settings may not be adequate.
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