01-14-2013, 04:49 AM
Robert M wrote:
The info you provided about the type of output is very unclear. You're describing the difference between step-wave and sine-wave output. UPSs with sine-wave output have always been preferable. Good clean a/c output is sine wave output. The UPSs you commonly see are usually standby models with step-wave output.
First, described UPS (with a spike of up to 270 volts) is an APC. Little difference between a step wave and so called sine wave output. Because all outputs are nothing more than a sum of sine waves. All are sine wave outputs. APC will forget to mention that .
To say more requires a parameter such as %THD. But to keep a consumer naive, many UPS manufacturers (ie APC) avoid that 'always required' number. What is 'dirty' power? %THD in manufacturer specs define 'clean' or 'dirty'. Some 'cleanest' power is when AC mains connects directly through a UPS to the appliance.
Difference between step wave and sine wave is relevant only when a number is provided. I have a 120 volt UPS described in advertising as a sine wave output. It outputs 200 volt square waves with a spike of up to 270 volts. They did not lie. Even high school math says that square wave or stepped wave output is only a sum of pure sine waves. Advertising hopes many will forget what is taught in math.
Second, step wave output is not harmful to electronics. Also forgotten when advertising myths replace science. That 200 volt square wave with a spike is made irrelevant by how electronics are designed. Electronics, even long before the IBM PC existed, are that robust.
Third, power draw is the myth that says do not connect a laser printer to AC mains. A printer (or any other motorize appliance) draws so much power. A specific number. So a UPS need only be sized that large or larger.
But, a UPS with sufficient power is still not recommended. Why? Because UPS power can be so 'dirty'. Ie step wave. A UPS can output more than enough power for a motorized appliance (printer). But its 'dirty' power, ideal for electronics, is also potentially harmful to small motors.
Advertising must avoid that reality. So advertising blames a "power hungry" printer. Otherwise you might learn (first point) how 'dirty' a UPS really is when in battery backup mode. And then you might also learn (second point) how robust electronics really are.
So again, point four: what anomaly does the OP wish to solve? That must be defined long before any suggestion can be posted.
One anomaly is a surge. Most surges are already made irrelevant by superior protection inside appliances. Same protection that also makes irrelevant a 'dirty' UPS. Concern is one type of surge that can occur maybe once every seven years. If any computer needs that protection, then so does the furnace, bathroom GFCI, clocks, refrigerator, and dishwasher. What most needs protection from the typically destructive surge? Smoke detectors.
Bill in NC has defined what always exists in every facility so that a potentially destructive transients does not cause damage. And what is necessary to protect household appliances. A technology well proven and routinely installed even 100 years ago. And is why every telco operates $multi-million computers, connected to exposed overwhead wires, without threat. That anomaly requires something called a surge protector. Completely different from another device - also called a surge protector - located adjacent to the appliance.
But again, which electrical anomaly must be solved. A $100 protector from Monster is only electrically equivalent to one also selling in Walmart for $12. But again, the always required numbers. Monster knows that a majority will believe advertising or price rather than learn simple spec numbers and basic science.
Numbers such as %THD or joules are essential for any honest recommendation. Numbers that are relevant only when the anomaly is first defined. View surge protection numbers for a UPS. Even the $12 Walmart protector may claim superior protection.
And that is the point. Subjective claims such as 'pure sine wave' are best called hooey.
So again, which electrical anomaly is to be elminated? Due to superior protection already inside electronics, even 'dirtiest' power from a UPS is ideal power.