Monitor flickers for a second while going from back up to online power

[BillP]

This question was originally posted by Abhishek on APC forums on 10/29/2016

---

I have a SMART ups SUA 2200i.I have just noticed an strange issue for the first time.Whenever the ups switches from battery back up to online the monitor flickers for a second.I don't think I saw this behaviour earlier or perhaps I just noticed it now.Is it a usual behaviour for the equipments such as monitors connected to smart UPS to flicker or lose power for about a second?The interesting thing is that  when the ups switches to battery back up there is no flicker or power loss for a second . So this is a case of finding out the reverse transfer time for ups.Any help appreciated.

[BillP]

This reply was originally posted by Nicole on APC forums on 10/31/2016

---

Hi Abhishek, 

Our Smart UPS line of UPSs have a typical transfer time of 2-4ms when switching from online to on battery and vice versa. It seems your monitor is just reacting to the transfer time of the UPS. As long as all your equipment stays on and is not being affected by the transfer time, I believe you have nothing to worry about. 

Regards, 

Nicole 

[Kiriakos_GR_apc]

This was originally posted on APC forums on 11/2/2016

---

You may also consider this possibility of PC monitor internal electronics at power supply as old and in need for refurbishing. 

If monitor this is 4~6 years old.

[BillP]

This reply was originally posted by Gareth on APC forums on 11/2/2016

---

It does sound like deteriorated capacitors as I have never noticed any monitor flicker, only light bulbs.

[BillP]

This reply was originally posted by Abhishek on APC forums on 11/4/2016

---

Well the equipment is being affected  as it is not performing optimally and this is irritating to say the least.But thanks for the info about reverse transfer time.Can you point me to any APC documentation/FAQ where reverse transfer time is mentioned (not transfer time).

[BillP]

This reply was originally posted by Abhishek on APC forums on 11/4/2016

---

Monitor is just 3 months old.Model is xl2420g from BenQ,not exactly cheap quality stuff.

[Kiriakos_GR_apc]

This was originally posted on APC forums on 11/4/2016

---

Few posts above Nicole wrote: Our Smart UPS line of UPSs have a typical transfer time of 2-4ms when switching from online to on battery and vice versa ... 

Now me as electrician I am aware that mechanical electrical relay specifications are not that tight. 

Usual relay at best this is 5ms when new, and it is possible this to further deteriorate due age? or simply because something got wrong at production stage.

Either way, anything it can be measured and inspected but not for end user him self.

According my book only a freelancer electronics repair specialist with true knowledge and lots of high-End tools he would find the problem and exchange anything bad with new. 

[Brad_C_apc · Accepted solution]

This was originally posted on APC forums on 11/5/2016

---

Relay switching time has nothing to do with transfer time on a SmartUPS. All the relay does is *disconnect* the line input, the UPS is already generating the required sine, just not switched onto the inverter. The transfer time is really the time for the UPS to decide the mains has dropped and the inverter to start. The relay's in a Smart UPS are there to boost/trim and disconnect the incoming line only.