Question 18 QMED02 - Electrician-Refrigerating Engineer

The Correct Answer is D **Explanation for Option D (220 volts AC):** The control circuit voltage in an industrial motor control schematic is determined by the voltage supplied to the components (like the contactor coil, overload relay contacts, and pushbuttons) shown in the control section of the diagram. Standard control diagrams, especially for smaller or simpler motor applications where 220V AC is the supply voltage, often use the line voltage (220V AC) directly for the control circuit. Unless the illustration (EL-0011, Figure A) specifically shows a control power transformer (CPT) stepping the voltage down (e.g., to 110V AC or 24V AC) or a rectifier circuit to convert it to DC, it is assumed that the control circuit operates directly off the provided supply voltage. Since the main supply voltage is stated as 220 volts 60 Hz (AC), and assuming the circuit is a common full-voltage non-reversing starter without a CPT, the operating voltage for the control circuit will be **220 volts AC**. **Why the other options are incorrect:** * **A) 110 volts DC:** This is incorrect. The supply is AC (60 Hz), and there is no indication that the voltage is stepped down to 110V *and* converted to DC for the control circuit. 110V DC is an uncommon control standard. * **B) 110 volts AC:** This is incorrect. While 110V AC (or 120V AC) is a very common control voltage, achieving this requires a Control Power Transformer (CPT) to step down the 220V supply. If the illustration (EL-0011, Figure A) does not include a CPT, the control voltage remains 220V AC. * **C) 220 volts DC:** This is incorrect. The supply is 220 volts 60 Hz, which is AC. Operating the control circuit at 220 volts DC would require a rectifier circuit, which is not standard unless specified for high-voltage DC coil operation.