Now you can prevent contactor chatter or Brown-outs when starting large loads or motors DOL. It is vital to know exactly what the secondary voltage drops down to under these conditions, although brief in nature they nonetheless pose a serious cause for concern particularly if contactor chatter or even brown-outs are to be avoided.
These conditions can easily draw current well in excess of the transformer full load current rating.
Transformers can take a degree of overload under this condition and although they may not be damaged, the secondary voltage will decay away and we need to know just what that secondary voltage will decay to.
The dangers arise from the risk of contactor chatter, even though this may be brief, the contactors can become damaged, or they may hold very lightly and could well exceed the thermal rating of the contacts in the contactor. This condition could become a very expensive hobby!
Now you can find the secondary voltage for all load conditions.
To use this program, simply input the transformer data from the manufacturer’s data sheet into the program and enter the load value (either in Amps or KVA), press CALCULATE and the program instantly displays the secondary voltage.
Once known, it is a relatively easy matter to contact the contactor manufacturer and ask the “hold on” value for that particular contactor.