Why is a relay typically used in a power window system?

Why is a relay typically used in a power window system?

• A. To reduce noise
• B. To adjust window position
• C. To protect the control electronics from the amount of current required to power the motor
• D. To provide weather sealing

Answer: (C)

Relays are used in power window systems to let a small, low-current control circuit operate a high-current motor safely. The window motor needs a fairly large amount of current, especially at startup, which would stress a normal control switch or driver if it had to carry it directly. The relay’s coil is energized by the control circuit with only a small current; that coil then closes heavy-duty contacts that supply the motor with the higher current it needs. This arrangement protects the control electronics from the motor’s current demands and voltage spikes, and also reduces wear on the cockpit switch by keeping the high current out of the control path. Weather sealing or noise reduction isn’t the primary purpose of the relay in this context.

Relays are used in power window systems to let a small, low-current control circuit operate a high-current motor safely. The window motor needs a fairly large amount of current, especially at startup, which would stress a normal control switch or driver if it had to carry it directly. The relay’s coil is energized by the control circuit with only a small current; that coil then closes heavy-duty contacts that supply the motor with the higher current it needs. This arrangement protects the control electronics from the motor’s current demands and voltage spikes, and also reduces wear on the cockpit switch by keeping the high current out of the control path. Weather sealing or noise reduction isn’t the primary purpose of the relay in this context.