🔍 Key Concepts
• Compare how many contactors or starter coils are shown and how many sets of main power contacts they control.
• Look for any extra components in series with the motor during starting, such as resistors, autotransformer windings, or separate motor windings.
• Understand that a simple direct-on-line (DOL) or across-the-line starter connects full line voltage directly to the motor with just one main contactor and overloads.
💭 Think About
• Count the number of main power paths from L1, L2, and L3 to the motor and note what devices are in each path before the motor terminals.
• Ask yourself: during starting, is there any way for the circuit to reduce the voltage or current to the motor (through resistors, transformer taps, or partial windings), or does it always apply full line voltage when the contactor pulls in?
• Compare what you see in the schematic to what would be required to switch between a reduced-voltage start and a run condition—do you see multiple stages of contactors, or only one?.
✅ Before You Answer
• Verify whether there is only one contactor coil (M or similar) and one set of main contacts feeding the motor, or multiple contactors labeled for different functions (such as start/run or high/low).
• Check if there are any resistors, transformer symbols, or separate motor winding connections drawn between the line and the motor terminals—if none are present, that rules out some options.
• Confirm that the overload (OL) devices are simply in series with each phase to the motor and are not being used to switch between different starting configurations.