ats switches in //

[zorgglub]

hello Gentlemen,
a company is suggesting to use 2x400a ats switches in // instead of a 800a...
as far as i remember , this is not a good idea , either in terms of repartition of current , and in term of switching timing.
do you have any idea about that ? any help welcome.
ps : this is for the emergency generators of an hospital in Haiti
best regards
Jean Mi

 

[davidbeach]

Divide the loads so that each can handle all of its load by itself or get an 800A ATS. Worst possible scenario is that on transfers and the other fails to transfer at all. Now you have the generator connected directly to the normal source. Bad, very bad.

 

[zorgglub]

Thanks Davis , i am going to ask thic company to review the design and go for a 800A ats switch.

best regards

jean mi

 

[zorgglub]

dear all,
here is the reply from the manufacturer of the equipment , and by the way , the max current is 1600 amps :

"Hello Jean,

From your attached drawings, there are two concerns.

1. The switches' transfer speed are slightly different. When the ATS transfers from one side to another at full load, the switch that transfer faster than the other will receive a large load current exceeding the rated operating current of the switch in micro-seconds. It could cause an unexpected trip or failure.

2. All of the switches' main contact has a micro-Ohms resistance when it closed. It will cause the load sharing unbalance between two 800Amps switches. For example, with a 1600Amp load, one of the switch provide 700Amps and the other one needs to provide 900Amps. It will cause an
unexpected trip or failure.

Therefore we don't suggest to use two 800A transfer switches to provide to a 1600Amps load. "

thanks for the support

Jean Michel

 

[waross]

Thanks for the update.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[wayne440]

Interesting that the manufacturer did not mention the possibility that a failure of one switch of a pair could create a connection to the utility.

 

[zorgglub]

indeed , and since the tranformer is a 13.200/208v , we will inject almost 14.000v in a 12.470 grid .
well , with the forum members support , i have now a strategy to correct those issues , many thanks.

best regards

Jean Michel