Machines; Special Control Circuits Flashcards
What is the purpose of timers?
Automatically turn electrical equipment on or off and conserve energy
What are the 3 basic types of timing devices?
1) spring-wound interval timers
2) mechanical and electronic time switches
3) timing relays
True or false; spring-wound interval timers provide a timed off interval
False, timed on. Ie. When dial is released a spring drives a clock mechanism which holds contacts closed for the set time
Parking receptacle circuits are an example of what kind of timed device?
Mechanical timer
Bathtub spa motors are an example of what type of timing device?
Spring-wound interval timer
Which type of timing device uses a small electrically driven clockwork motor to control adjustable trip mechanisms?
Mechanical timers
What type of timing device do we commonly see in motor control applications? Why?
Timing relays. Because they are precise and versatile.
What are 3 methods of controlling timed operation on timing relays? Which of these methods is the most popular? Why?
Pneumatically (by air),
Electronically,
Or by a fluid-filled dashpot.
Electronically. Because electronic timing relays are smaller, more accurate, versatile, and cost-effective.
What kind of timing device can control devices over 24-hour or 7-day timing cycles.
Mechanical timers
What are the two basic types of contact actions for timing relays?
Time delay on energization (TDOE) and time delay on deenergization (TDOD)
What is a “delay on operate” contact action?
Delay on energization
What is a delay on release contact action?
Time delay on de-energization
Which type of contact action changes the normal condition of the relay contacts once the set time has elapsed?
Tdoe
What type of contact action Returns the contacts to their normal position once the set time has elapsed?
TD OD
What type of contact action would be used to allow a conveyor to empty Itself by running for a set time after the loading equipment has stopped?
TD OD
What type of contact action would be used for switching in windings during the starting of a part winding start motor?
TD OE
On a multi-function electronic timing relay what do the first four dip switches control?
The function of the relay
On a multi-function electronic timing relay what to do the last 3 dip switches control?
They determine the range of the timer
On a multi-function electronic timing relay what does the dial set?
The time delay within they selected timing range
What are three additional functions that may be included with dip switch programmable multifunction timing relays?
Interval timing
one shot timing and
repeat cycle timing
What is it called when:
- timed contacts change condition immediately -stay changed for a specified time
- return to their normal condition, even if the relay remains energized.
Interval timing
Give an example of the application of interval timing
Controlling an exhaust fan to purge a combustion chamber.
What kind of timing requires power to be applied to the relay and a start terminal on the relay
One shot timing
What type of timing function begins each time the start terminal receives a signal?
One shot timing
