Examkin

Question

Difficulty: HardSwitches and Relays

A technician is designing a control system operated by a single manual toggle switch. When the switch is actuated, it must simultaneously disconnect an existing 12 V DC cooling fan and connect a separate, electrically isolated 120 V AC warning beacon to power. Which switch configuration is the minimum requirement to control both isolated circuits in opposite states with a single mechanical actuator?

  1. A
    Double-Pole, Single-Throw (DPST) switch
  2. B
    Single-Pole, Double-Throw (SPDT) switch
  3. Double-Pole, Double-Throw (DPDT) switchAnswer
  4. D
    Single-Pole, Single-Throw (SPST) switch

Answer

Double-Pole, Double-Throw (DPDT) switch
The Double-Pole, Double-Throw (DPDT) configuration provides two electrically separate poles (required for isolating the 12 V DC and 120 V AC systems) and two throws per pole. This allows Pole 1 to open the 12 V DC fan circuit while Pole 2 simultaneously closes the 120 V AC beacon circuit under a single mechanical toggle.

Step-by-Step Solution

1
Determine the required number of poles based on circuit isolation.
Two poles (Double-Pole) are required.
The system involves two distinct voltage sources (12 V DC and 120 V AC) that must remain electrically isolated to prevent dangerous short circuits or cross-voltage damage.
2
Determine the required number of throws based on contact operation.
Two throws (Double-Throw) are required.
When the switch is actuated, one load must disconnect (normally closed contact opening) while the other load connects (normally open contact closing), requiring two contact positions per pole.
3
Combine the pole and throw requirements.
DPDT configuration.
Two independent poles combined with two selectable throws per pole define a Double-Pole, Double-Throw (DPDT) switch.

Key Concept

Switch Pole and Throw Nomenclature and Electrical Isolation
Estimated Time:1m 15s
Rate this question

Topics

Switches and Relays

More questions from this topic