No power being input after switching from utility power to Generator

Anonymous user · ‎2021-06-30

Dear all,

I am using Smart-UPS RT 2000VA and when it's connected to the utility power it's working perfectly fine, only thing that the battery is wearing out(almost 3 years). My problem is, when I switch the power source to generator, my UPS unit doesn't receive any power, it has to run on battery.
When I tried to plug in my server direct to the power source which was suppose to connect to the UPS, it works.
I wonder why my UPS doesn't work when the generator is being used in the place of utility power.
please help. Thanks!

Javik_apc · ‎2021-06-30

Lights and most motors do not really care too much about the power line frequency. Computers tend to be more sensitive to it.

What is the model/brand of generator? Is there a tachometer on it?

The engine speed regulation may be slightly off, so that results in too high or low frequency which the UPS doesn't like. Engine speed is usually some multiple of 50 or 60 depending on your country.

For example, in the USA, small portable generators commonly spin at 3600 RPM (60 cycles per second * 60 seconds).

The fix may be as simple as slightly increasing or decreasing the engine's governor speed.

See Answer In Context

BillP · ‎2021-06-30

Smart UPS RT are usually very good at running on generator power due to the nature of their design. I'd would check your input voltage and frequency to the UPS with a voltmeter or scope to see if they are okay. Alternatively, if you have software or a network management card installed, you can check in there to see why the UPS is going to battery.

on these models, there is no sensitivity setting like on line interactive smart ups. I'd start with the voltmeter/software/NMC if you have one to see what is going on.

we also have [this article|http://nam-en.apc.com/app/answers/detail/a_id/7354/] but as I mentioned, Smart UPS RT does not have a sensitivity setting.

Anonymous user · ‎2021-06-30

Thanks for your reply.
the voltage is around 236V, however, I could not find out the frequency.
For your information, all other electrical equipment(air cond, lights etc) are working well with the generator.
Yes, I do have the software connected to the UPC unit, it says power failure, running on battery.

Javik_apc · ‎2021-06-30

Lights and most motors do not really care too much about the power line frequency. Computers tend to be more sensitive to it.

What is the model/brand of generator? Is there a tachometer on it?

The engine speed regulation may be slightly off, so that results in too high or low frequency which the UPS doesn't like. Engine speed is usually some multiple of 50 or 60 depending on your country.

For example, in the USA, small portable generators commonly spin at 3600 RPM (60 cycles per second * 60 seconds).

The fix may be as simple as slightly increasing or decreasing the engine's governor speed.