Computers And Industry

Using A Computer On Generator Power


If you are in the midst of an extended power outage and are fortunate enough to have a generator that you picked up from the local department store, then you are probably are a bit miffed when you find out that your Battery Backup, cell phone, laptop, or any other electronic device for that matter, does not charge.

Well, the reason is quite simple. The generator isn't putting out clean, or more appropriately, utility quality power.

Now, because of the unclean nature of the power, your battery backup sensing circuit switches over to battery mode. And of course while the battery backup is in battery mode, no incoming power is allowed to pass through the charging circuits, which in turn, results in the internal battery not charging.

SPECIAL NOTE: While on generator power, you might hear your Battery Backup constantly clicking on and off. This is because your generator is outputting variable power quaility. For 1 second, the generator is outputting power that means the clean standard, the next second the generator is outputting power that isn't clean. It is this variability that your battery backup is sensing and thus is responding to in kind.



Utility (Clean) power is alternating current at a consistent voltage of 120 volts and a consistent frequency of 60 Hertz. Generator (Dirty) Power is random in nature and fluctuates from the Utility power constants. To better understand why a generator creates dirty power, please refer to the following.



A generator is comprised of a motor plus an alternator. The motor spins the alternator and thus produces an alternating current at a specified voltage and frequency. A voltage regulator controls the output voltage. However, the frequency is very dependent upon the rotational integrity of the motor; i.e. a constant revolutions per minute (RPM).

Since the engine is a simple gas engine, variabilities to a constant RPM can be introduced such as bad quality gas, loads on the alternator which result in engine torque compensation, and non consistent explosion yields at the piston level. These all serve to increase variability in the frequency and voltage outputs of the generator. In a nutshell, this is what causes dirty power.

How A Battery Backup Acts When It Detects Dirty Input Power

When a Battery Backup detects dirty power, the sensor circuit switches the battery backup to battery mode. This is the clicking sound you hear. Th



As is seen above, if the battery backup is in battery mode, no charging occurs...even though the generator is providing power. The result is that the battery never charges and eventually, the batteries discharge completely, and no power to your computer is available. More precisely, you can see that when in battery mode, switch A is open thereby shutting off power to the charging circuits and switch B is closed thereby passing power from the battery to the inverter and out through the recepticals. So, in a nutshell, the ultimate goal is to keep the voltage and the frequency at enough of a constant such that the charging circuit interpretes the incoming line voltage / frequency as stable.



Now note that one could put a line conditioner in line before the battery backup, however, a line conditioner will only fix the voltage level issues. It does nothing to address the variations in frequency. Therefore, we need a more complex solution.

The Solution: Utilize A UPS That employs a Double Conversion Topology

The UPS should provide continuous pure sine wave output by converting AC power to DC power and inverting it back to pure sine wave AC output. The output power should be commensurate in quality to the power from the utility company; free from harmonic distortion and electrical noise. Also, it should have a wide tolerance of AC line input so that it can handle the power output from a generator.

Some of the characteristics of a Double Conversion Topology UPS are:

1) Continuous protection of load is provided from the inverter, whether it originates from the AC-input supply or the battery.

2) Isolation of the load from the upstream distribution system, thus eliminating transmission of any upstream fluctuations such as spikes and over voltages to the load.

3) Very wide input-voltage tolerances and precise regulation of the output voltage.

4) Precise regulation of the output frequency and possibility of the UPS operation as a frequency converter (if configured for this purpose) by disabling the static switch.

6) Much superior performance levels under steady-state and transient conditions.

7) Instantaneous transfer to stored-energy mode in the event of an AC-input supply failure.

8) No-break transfer to bypass mode.

9) Manual bypass designed to facilitate maintenance.

One such example of a Double Conversion Topology UPS is the Cyberpower SmartApp OL1000RTXL2U. The cost is about $500.00 on the web. It provides about 900 Watts.



If you get this unit, or one like it, during a power outage, you can plug the unit into the generator line. Then, you can simply plug your computer into the unit and voila, your good to go.

OR.........

You can plug your existing line conditioner into the UPS, then plug your existing battery backup into the Line Conditioner. Then plug in your computer to the existing battery backup. THIS IS DAISY CHAINING AND ALL THE MANUFACTURERS SAY IT VOIDS THE WARRANTY! SO DON'T DO IT! (wink, wink).

TECHNICAL NOTE: It is possible to purchase a generator that does have sine wave output power output quality commenusurate to utility power. Generac is one dealer that provides this and some fixed installation generators may have this quality as well.
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