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solar8484

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60Hz - > 16.6 ms period time. So 3-5ms switching time will not noticed by 99.99% of home equipment. But do not mix relay/contactor switching time with system transfer time (time between power failure and switching complete). Some system may be slow on power failure detection. Actually most of home electronic/electric devices will work without interruption if complete switching time is below 200-300ms.

It also depends on where on the AC voltage wave cycle when switching happens which is likely random for power outages.
 

OffGridInTheCity

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do solid state relays operate faster than contactors brewmatic has stated that 3/5 ms is fast enough to work most things in the house i would settle for that
The reason I have Go-Power / Progressive ATSs, which are mechanical and therefore limited in speed is for the power levels I need. Progressive ATSs do 240v@50a - needed for whole house heat-pump compressor, cooktop, dryer, hot water heater, etc. The Go-Powers do 120v@30a which is also needed for the loads that I have wired in.

I might suggest that part of this discussion is the level of power needed. I'm not sure how much power you can push thru modern day solid state relays?

The way MPP Solar off-grid units )(with battery) handle this is thru the mode where output is DC -> AC. The incoming AC is converted to DC so you have AC -> DC -> AC. This design facilitates UPS being built-in (and battery charging). Its clever and if they had been available (and I understood it) back 3 years ago - I may have gone that direction for off-grid.
 
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robbymax

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60Hz - > 16.6 ms period time. So 3-5ms switching time will not noticed by 99.99% of home equipment. But do not mix relay/contactor switching time with system transfer time (time between power failure and switching complete). Some system may be slow on power failure detection. Actually most of home electronic/electric devices will work without interruption if complete switching time is below 200-300ms.
do solid state relays operate faster than contactors you stated that 3/5 ms is fast enough to work most things in the house i would settle for that but how do i do it
 

brewmatic

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do solid state relays operate faster than contactors you stated that 3/5 ms is fast enough to work most things in the house i would settle for that but how do i do it

Most mechanical switches (relay/contractor) are fast enough for in-home consumers. However control circuit is slow in many cases. It could be a long delay between actual power failure and contactor engagement.
 

DerpsyDoodler

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is it the transfer switch or the contactors i suspect both
A faster transfer switch alone will not solve your problem. It might kill some electronics, though. You need an inverter that synchronizes its waveform to the grid's (or whatever alternate power source's) waveform. This is the only way to ensure a smooth uninterruptible transition without smoking anything. In lieu of replacing your inverter, you could add small UPSs to the loads that you experience problems, with.
 

efficientPV

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If you are clever, you can wait for the two waveforms to sync and switch at that time. If the inverter and line are only a fraction of a Hertz off, they will line up every couple seconds.
 

RCinFLA

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You don't want to use a triac based solid state relay as they have over a volt of switch drop. This requires they have a heat sink. Their switch speed is usually determined by their LED opto isolator and triac turn off switching speed is limited to a half cycle of AC, as triac does not shut off until next zero voltage crossing after their gate control drive is shut off. Triacs are also more vulnerable to AC input spikes due to grid lightning strikes.

Relays are normally good enough but the time it takes for inverter to recognize the grid drop is added to relay time. My SW4048 inverters I use for whole house UPS have been running for over 20 years and I never get a reset on clocks, computers, or DVR. It uses a Deltrol Controls 375 three pole relay for 60 amp pass-through on inverter. The Deltrol relay spec is 15 millisecs closure and opening time which is about one AC cycle.

These inverters are always running in parallel with grid so unless the grid significantly loads down the inverter voltage before the relay releases from grid the output AC keeps up. These low frequency inverters have more surge current capability then high frequency inverters. Opening the relays under high back surge current of a collapsed grid is tough on relay contacts but, knock on wood, they have held up for over twenty years. I probably get two or three grid glitches per week on average that cause inverters to release from grid.

Many HF grid synchronous hybrid inverters have to go through a mode change on their DC-HV DC converter first stage which increases their time for going from float charging to supplying inverter output power. LF inverters do this immediately.
 
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efficientPV

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You have to be really good at electronics to use a triac in this application. It is so easy to have the two sources on at the same time making a horrendous short.
 

RCinFLA

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You have to be really good at electronics to use a triac in this application. It is so easy to have the two sources on at the same time making a horrendous short.
Yes, with out of phase AC on both sides of a triac bad things can happen.
 
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robbymax

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out of phase AC on both sides of a triac bad things can happen.ok so solidstate relay is not a good idea but you keep telling me this is a bad idea and that wont work i have got this system working 99% and i can see there is a lot of talent out there but no body is saying sounds like i know but i not going to tell you, thanks a lot chaps
 

robbymax

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You have to be really good at electronics to use a triac in this application. It is so easy to have the two sources on at the same time making a horrendous short.
no it is not easy to get 2 sources joined my inverter is on all the time ready to be used the mains is on all the time each with its own contactor that
is switched in and out by a two way switch now what is the fastest switch and what are the fastest contacters? is there something special out there
 
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solar8484

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Freewheel a 1800 rpm 5 hp motor. That will fix it. what is this all about please explain

If you really want to go down the rabbit hole then you can research synchronous condensers. Is a 5HP motor really what you want to be running all the time? It's not what most would consider a practical solution for a home.
 

robbymax

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then why suggest it, you sound like you could have an idea on how to fix this come on lets hear it, there must be more than me with this problem
i have made a few suggestions and been told no way would they work, but nobody has got an idea of there own
 

solar8484

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then why suggest it, you sound like you could have an idea on how to fix this come on lets hear it, there must be more than me with this problem
i have made a few suggestions and been told no way would they work, but nobody has got an idea of there own

Why do you think that? Several people have suggested UPS for the loads (e.g. TV/computer/clocks) that reset during power transfer. That's the most common solution.
 

Hedges

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A ferro resonant transformer would carry a load through for a couple cycles (but at the cost of constant power dissipation).
They could be suitable for critical loads.



An on-line UPS (battery charger --> battery --> inverter) would be another solution.
Many loads run off 12V DC, so skip the inverter. I plan to do that for DSL, router, VOIP dongle, etc. and add PV to the mix.

The ferro resonant transformer might be better at tolerating poor power quality, unless the UPS was well hardened against that.
 
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