AnswerBun.com

Hot neutral in UPS devices in battery mode

Engineering Asked on January 6, 2022

I have faced a problem with ITYS E-3KVA UPS device. While operating in the in-line mode the measured neutral-ground voltage is almost equal to zero. However, during the battery mode the neutral-ground voltage is equal to 102 V. Knowing that the UPS is properly grounded and the wiring network was checked many times and everything was ok. This neutral-ground voltage caused a serious damage to the medical devices we use. Could you please provide me with a thorough analysis, from your point of view, and tell me how to overcome this problem. Thanks in advance

One Answer

This was more complicated than I thought. The APC web site says

While "On Battery," safety agencies ... require the UPS input connections to be disconnected from the utility input to prevent "backfeed" power/voltage from the UPS batteries being applied to the UPS input terminals. Because the Neutral must also include this "backfeed" protection ..., the output Neutral to Ground voltage will "float" to approx half the voltage between output Line & Neutral. For a 230Vac system, the N-GND voltage can be 115Vac.

They don't want you to backfeed so you don't electrocute the workers trying to fix things.

APC goes on to say:

If the UPS output must have a N-GND connection for zero volts while the UPS is "On Battery," an output isolation transformer must be attached to the UPS output so that a new N-GND connection can be made without creating a ground loop.

If it were my equipment, I would open it up and connect neutral and ground, with an interlock so you have to be physically disconnected from the mains to make the connection.

Another idea is to have a transfer switch such as is used with a generator. When the circuit is to be powered from the generator, you are physically disconnected from the mains. If you wire it correctly you could have the N-GND connection with a transfer switch. This is not a UPS but it will keep you from blowing up your equipment.

I think your best bet is to get the isolation transformer. It would not be as much fun as reworking the equipment but it also won't void your warranty.

Answered by user1683793 on January 6, 2022

Add your own answers!

Related Questions

historic construction method resources

1  Asked on April 30, 2021 by dleon

 

Blade efficiency of a franscis turbine

0  Asked on April 29, 2021 by ganish-ananth-a-m

     

Significance of asymptotes in root locus

1  Asked on April 28, 2021 by p-krishna-chaitanya

   

Calculating Pipe Leak Flow Rate

1  Asked on April 28, 2021

 

250W 24V Motors

2  Asked on April 27, 2021 by cyrus-murray

       

Is this dropout design as bad as I think?

4  Asked on April 24, 2021 by morgan087

 

How can propeller blades be made silent?

2  Asked on April 22, 2021 by user11937382

   

Ask a Question

Get help from others!

© 2022 AnswerBun.com. All rights reserved. Sites we Love: PCI Database, MenuIva, UKBizDB, Menu Kuliner, Sharing RPP, SolveDir