- Reaction score
- 13,478
Time to unveil the new starter in operation. In the starter itself to the very left we have the timer, which I set to make the transition a little later than the pneumatic one was set, so that the blower is very nearly at full speed and the current a few amps lower when it happens. Then there is the overload relay, in the delta loop so set at FLC/sqrt(3) or about 4.5A for a 7.7A FLC. Then the line contactor, with the start button mounted on top, the delta and star contactors with a dual N/C interlock contact mounted across them (there's a mechanical interlock hidden inside too) and the isolator. In the box above is the monitoring relay and the auxiliary supply contactor slaved off the line contactor. The two sets of three brown 2.5's at the bottom are the two ends of the windings.
When you press the start button, provided the monitoring relay and O/L are normal, you start the timer which outputs a feed to the star contactor coil. This operates and its aux contact extends the feed to the line contactor which also operates, holds via one aux contact and bypasses the star aux with another. This sequence, rather than making the line contactor hold directly, proves that the delta is out before anything can happen, as an operated delta would prevent the star operating both electrically and mechanically. When the time elapses the star coil is de-energised, releasing the interlock and allowing the delta to operate.
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When you press the start button, provided the monitoring relay and O/L are normal, you start the timer which outputs a feed to the star contactor coil. This operates and its aux contact extends the feed to the line contactor which also operates, holds via one aux contact and bypasses the star aux with another. This sequence, rather than making the line contactor hold directly, proves that the delta is out before anything can happen, as an operated delta would prevent the star operating both electrically and mechanically. When the time elapses the star coil is de-energised, releasing the interlock and allowing the delta to operate.
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