What about them does not play well together? Are the soft start manufacturers making junk that will be problematic in the long run?
It has to do with the current and voltage wave forms caused by the soft starter chopping the sine wave.
Many AVRs have trouble properly sensing the voltage of the interrupted sine wave.
Our thinking at this point would be that automatic shedding (total load current, frequency, and voltage sensing) to drop the AC units if necessary should be adequate, since plugs and lights will be well below the 4 kw surplus we show available here.
That is a road that I have traveled many times.
I installed a lot of standby sets in the tropics.
Anyone who could afford a standby set generally had a lot of A/C.
A lot of sets were brought in in one order. All were sized by someone else and all were undersized.
My first learning experience:
The power failed and the set started and transferred automatically.
The A/C load caused the voltage to drop so far that the contactor in the ATS opened.
The set recovered speed and voltage.
The ATS reconnected and the A/C load pulled the frequency down again.
This repeated until the repeated arcing in the contactor burned one of the main contacts so badly that it no longer made contact.
Then at least the lights came on. (Half of the lights powered by the remaining contact and the remainder powered in series with the stalled A/C units.
Solution:
Small relays were installed in the A/C control circuits.
A push button would energize the relay and one set of contacts would seal the relay in, a second set would control the A/C.
When the power failed, all of the relays would drop out and the standby set would come on-line with no A/C load.
The owner would then select which individual A/C units to restart, within the capability of the gen-set.
There are also compressor protection relays available.
The three phase models monitor voltage, and phase sequence.
They will not operate if the voltage is too low or too high.
They will not operate if the phase sequence is reversed.
I used one of these and a lot of control relays to protect all of the refrigeration equipment in a sausage factory.
One day the utility changed out the transformers and put 416 Volts into a 208 Volt system.
They lost computers, calculators, lights, fax machines, and copiers.
The protection system saved all of the refrigeration equipment and no product was lost.
The single phase protectors were generally plug-in devices intended for refrigerators, freezers and small A/C units.
They would shut down on over voltage or under voltage. They provided automatic restart after a random time delay on the order of three minutes.
You may roll-your-own with a time delay relay that drops out on a power failure and re-closes after a suitable time delay that allows time for the large motor to start.
Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!