Problem
Coffeeshop in Serangoon experiencing tripping problems everyday and usually occur in the morning when stall owners are running their induction cookers to prepare for the day. The high ampere from the induction cookers cause the main outgoing MCB to trip at the distribution board, and sometimes even trip to the upstream HDB supply distribution board.
As this coffeeshop is limited to a load of 100A, we recorded that during peak periods, the load can go up to 90A or higher per phase. We also recorded that the neutral return had about 25A. This meant that the single phase loads are very high, therefore causing the tripping issue.
Solution
As instructed by our LEW, Mr Wong, who have been handling this coffeeshop for quite some time, told us to help to add a 2 step capacitor ( 2 x 15kVar) where the 2nd step comes in by a timer.
With this, we recorded that the power factor had improved by about 30% (from 0.6 to 0.9) and current per phase has dropped to an average of 70A.
However, the problem still persisted even though the capacitor bank was added.
In the end
The building LEW is involved and after their investigation, they realized that the HDB supply distribution board MCB was undersized.
Even though our capacitor bank did not completely negate the problem, but it helped to alleviate the high current tripping issue and the tripping became less frequent. Also, with the power factor correction of 30%, it will help the coffeeshop save electricity bills by at least 10-20%.