Testing A UPS

[Bira]

Hi;
Can anyone help me clarifying/providing the following infomations regarding testing a UPS. (3phase, 120KVA)
- Any good site where I can find information about UPS testing procedures,test plan, methods, testing set up for UPS and probably some test results.
- While testing the UPS, how the UPS is loaded for efficiency test like "efficiency test at 95% of the load" etc? Do we really load the UPS or the load is simulated. If simulated which are the testing devices available for simulation.

thank you in advance for all your replies.

 

[RonShap]

Most manufacturers will have a standard commissioning/start up procedure documented for different models.
I would suggest that if power distribution breakers make it possible, to simulate the load with a load bank (large banks of resisters [sometimes reactive components too if needed]).

 

[alehman]

This is somewhat of a specialty. You may want to consider hiring a firm that experienced in commissioning this type of equipment. There are a number of them around (like mine).

 

[candu6]

You can buy resistive load banks that have a number of resistors that can be switched in to create the desired amount of load. In one case we simply wired our 120V inverter to a distribution panel and connected that to a number of ceramic heaters to serve as a 100A total load. That was a cheap and dirty load test, but it did the trick.

 

[EEIre]

The following are some UPS tests which I have done in the past on UPS systems.

1) Battery Discharge Test: This is probably the most important UPS test.
1.1)Set up the UPS with a load bank, increase to full load. 1.2) Put a waveform analyser on the output.
1.3) Fail the input power supply.
1.4) Check the output waveform to see if the load was uniterrupted.
1.5) Run for the rated battery autonomy while noting battery voltage and current every minute

2) Changeover test
With a waveform analyser on the output switch the load using the static switch and check if the load is not uniterrupted.

3) Alarms
Simulate all the alarms and check

4) Meters
Check all the meters against a calibrated multimeter

5) Voltages and Frequencies
Check if the rectifier and invertor output voltages and frequences are in spec and adjust if necessary

 

[mc5w]

You could also use some electric space heaters of the forced air type for your load bank. This is the cheap way. The portable types that are mounted on wheels and use a 3-phase power cords would provide some amount of extra utility if you have some places that need occasional electric heat when not testing the UPS.

 

[Bira]

Thanks all for your responces. Thanks Seanmx which is very clear on the things that I am looking for. It gave me a good way to start with. I will like to know more about the testing equipments I neeed for these equipments & again UPS loading.
My concern is...UPS is going to see a veriety of loads during its life cycle. If I will test with the Resistive load, how am I taking care of the actual/real load?

thanks again in advance for all your responces.

 

[MikeHalloran]

Don't focus just on the total removal of input power.

The toughest part to design, and the toughest part to test, is the power fail detection circuit, the part that actually decides when to change energy sources.

You need to check for proper operation with slow and fast developing brownouts, overvoltage surges, missing cycles, and all of those in combination ... or just move to SE Florida, where the award- winning electric utility company provides UPS tests on a daily basis.



Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

 

[alehman]

First you need to determine what type of UPS you have. There are fundamentally two flavors.

One type is variously called standby mode / line-interactive / off-line. These systems feed conditioned utility power to the load until the utility source fails. They transfer the load to an inverter when the utility fails. The inverter draws power from the battery. There are several variations of this type of system. They are fairly susceptible to failure during input transient events as Mike says because the transfer switch must be able to detect the transients, switch on the inverter and transfer the load all in a few milliseconds.

The other type of UPS is called double-conversion or on-line. This type feeds the load from the inverter at all times. The inverter takes its power from the DC bus which is fed from a rectifier and battery. During normal operation the rectifier supplies power to the DC bus and the battery "floats". When the input power fails, the rectifier output goes away, so the inverter begins to pull down the battery.

If your system is an off-line type, perhaps some type of input switching system with a contactor could be used to simulate transient events. A variable voltage transformer (variac) could be used to simulate varying voltages. For 120kVA, that may be manageable. I've never seen this type of testing in the field however.

Double-conversion systems are generally not affected by transient outages and varying input voltage because the output is a regenerated from the DC bus. That's not to say the input stage (rectifier) may not fail, but the output being isolated from the input would continue to be powered by the inverter until the battery runs down.

Testing double conversion systems typically includes a number of simulated power failures, extended operation at varying load levels, waveform measuremetns and battery capacity tests. As Mike eluded, the size and cost of equipment to simulate rapid transients and varying votlage is generally prohibitive for field testing large systems.

Keep in mind that about 98% of UPS failures are related to the batteries.

See:
faq238-270
ftp://ftp.gbutler.com/pub/cfg/battery-cx-article.pdf

 

[ScottyUK]

Depending on your overall UPS system design, you should also check how the UPS behaves when it is on generator supply. The generator supply is always a lot 'softer' than the utility, so frequency and voltage stability are not so good.



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