Non Linear Loads- UPS Selection

[BillP]

Dear APC team,

Can you give some suggestion for what kind of UPS we can use for the Non linear Loads like Motors, Pumps, Compressor Loads.

Can you give the model name of the smart UPS less than 10 KVA loads?

Thanks in advance.

[chefash_apc]

APC will tell you that most Smart UPS units are rated for computer room equipment and not for motor loads.

However, in real life, many Smart UPS systems have a decent 3:1 crest factor, so they can handle various types of loads.

Step 1, is get a good Fluke with inrush current measurement feature and look for peak amperage of the total load including startup.

Step 2, size the UPS at 80% of that max amperage... remember VA is volts x amps.  So a 20amp amperage at 230v will need 4600va (6kva)

When we do it for our machines, we also add a isolation transformer as well.  The SURT003 model is nice.

[Anonymous user · Accepted solution]

I'm doing something similar and here is what my research on this:

- Check any 240v UPS to see if it has balanced or unbalanced output.  Motors may appear to work with unbalanced output but depending on the degree of the voltage unbalance it will cause the motor windings to overheat and motor efficiency to drop. 

- see apc FAQs:  Hardwiring to 120v, 208v, and 240v loads from a 208v/240v SmartUPS RT UPS

- i've ordered an isolation transformer SURT003 to match my SRT5kXLT which should provide balanced output of around 5kVA for my single phase 240v motor.  

disclaimer: I'm not a professional, just sharing what i've found for a project im doing.