What is T
ime delay relay?
Timing relay has a device that delays the instant switching on or off of the armature when power is applied to or removed from the relay.
Some relays are built with a kind of “shock absorber” system connected to the armature, which prevents instant complete movement when the coil is either energized or de-energized.
Types of time delay relay:
The following is a description of the four basic types of time-delay relay contacts:
NOTC (normally-open, timed-closed):
When the coil is unpowered (de-energized), the NOTC (normally open, timed-closed) contact is normally open. It is closed by applying power to the relay coil, but for the specified amount of time only after the coil has been continuously powered.
The direction of the movement of the contact (either closing or opening) is the same as a standard normally open contact. Because the delay occurs in the direction of coil energization, this type of contact is alternatively known as a normally-open, on-delay.
NOTO (normally-open, timed-open):
Unlike the NOTC contact, the timing action occurs upon de-energization of the coil rather than upon energization. Because the delay happens in the direction of de-energizing the coil, this sort of contact is known as a normal-open, off-delay contact.
NCTO (normally-closed, timed-open):
The NCTO (normally-closed, timed-open) contact is normally closed when the coil is unpowered (de-energized). The contact is opened by applying power to the relay coil, but for the specified amount of time only after the coil has been continuously powered.
The direction of the movement of the contact (either closing or opening) is identical to a standard, normally closed contact, but in the opening
NCTC (normally-closed, timed-closed):
The contact with the NCTC (normally closed, timed-closed) is like the NCTO contact, because it is normally closed when the coil is unpowered (de-energized) and opened by applying power to the coil.
Applications of Time delay relay:
Flashing light control (time on, time off):
In conjunction with each other, two time-delay relays are used to provide a constant frequency on / off pulsing of contacts to send intermittent power to a lamp.
Furnace safety purge control:
The air fan must operate for a defined quantity of moment to “purge” the furnace chamber of any possibly flammable or explosive vapors before a combustion-type furnace can be lit securely. A time-delay relay offers this needed time component for the furnace control logic.
Motor soft-start delay control:
Instead of starting big electric engines by switching complete power from a dead-stop condition, decreased voltage can be switched for a “softer” start and less inrush current.
Conveyor belt sequence delay:
When multiple conveyor belts are arranged to transport material, the conveyor belts must be started in reverse sequence (the last one first and the first one last) so that material doesn’t get piled on to a stopped or slow-moving conveyor.