This tool allows an exploration of how a Direct On Line (DOL) starter works.
These motor control devices switch a motor on or off with no varying speed or reduction
in starting current. They are suitable for small, low-powered motors and can be used for single or
three-phase applications. The unit contains an electromagnetic coil that operates a contactor.
The unit also incorporates overload contacts, finely tuned to the motor's start and running current
to trip the device should an overcurrent occur. The coil that operates the contactor also provides
undervoltage protection, as the contactor will open should a voltage lower than the coil voltage
rating occur, e.g. during loss of supply. This means that the machine will not automatically
restart unexpectedly should power resume.
Undervoltage: Simply a power cut. BS 7671: requires undervoltage protection
on any machine where the sudden re-starting of the machine may cause a danger.
Using motor controls that require somebody to manually switch the machine back on
after a power cut provides undervoltage protection.
The tool is not fully complete as the hold on checkbox needs clicking manually on starting and stopping.
