L1 - Motor - Review Quiz Flashcards
(34 cards)
What is the difference between a schematic diagram and a wiring diagram?
Schematic:
- uses symbols to identify components.
- interconnecting lines to show electrical continuity
Wiring:
- shows the relative layout and how the component are wired
What is low voltage release? (LVR)
- 2 wires
- When after a power failure: the machinery restarts on its own
On a magnetic starter (combination style) what is horsepower rated?
- The contact (power)
- The disconnect switch
- The magnetic contactor
What is another name for a zero speed switch?
Plugging switch
* Zero-speed switches are used in circuits to provide either plugging action (momentarily reversing a motor to stop it) or anti-plugging action (preventing the reversal of a motor until it has come to a rest).*
How does a latching relay work? What is the purpose of the unlatching relay?
Latching relay is energized after de-energization is mechanically held in place to release energize unlatching coil.
*** A latching relay is an electromechanical switch commonly selected when the operator must control (either switch off or amplify) a large amount of current flow. It will remain in the last position it was when last powered, whereas a non-latching relay will return to its typical position.’
What is the purpose of a limit switch?
To prevent over-travel
* A limit switch is an electromechanical device operated by a physical force applied to it by an object. Limit switches are used to detect the presence or absence of an object. These switches were originally used to define the limit of travel of an object, and as a result, they were named Limit Switch.*
What is the dotted line between the forward coil and the reverse coil on a schematic drawing?
Mechanical interlock
* Represented on schematic diagrams as a dotted line between the two coils, a mechanical interlock is a physical barrier that is pushed into the path of one coil’s armature by the movement of the adjacent coil. This means that even if both coils are energized, only one armature will be able to pull in fully.*
Name three pressure switch types
1- Bourdon tube: when the pressure inside the tube increases the closed end of the C opens out, thus the displacement of the closed end becomes a measure of the pressure. A C-shaped Bourdon tube can be used to rotate, via gearing, a shaft and cause a pointer to move across a scale.
2- Bellows: When pressure is applied to the closed-end, such as in the animation below, the bellows will be compressed. The closed-end will move upwards and the link, which is the rod in between the closed-end of the bellows and the transmission mechanism, will go up and rotate the pointer.
3 - Diagram: A diaphragm is nothing more than a thin disk of material which bows outward under the influence of a fluid pressure.
* Each of these devices converts a fluid pressure into a force. If unrestrained, the natural elastic properties of the element will produce a motion proportional to the applied pressure.*
Name 2 type of timers
- On-delay (electronic)
- Off-delay (pneumatic)
What is the purpose of a control relay?
To offert more contacts and a diverse control cct.
What type of oil is used in a dashpot timer?
Silicon
Dashpot timer: The dashpot timer is a fluid time-on-timer that can be used in definite time motor acceleration starters and controllers. A dashpot timer is a container, a piston, and a shaft. The dashpot timer functions when a magnetic field forces a piston to move within a cylinder when the coil is energized.
On/off delay timers can be changed by rotating the timer face of X degrees
180
Name 2 type of contactors
1- Plunger: Vertical lift
2- Clapper: front closing
What is the difference between a magnetic starter and a contactor?
- Magnetic starter has O/L protection
-Magnetic coil is a part of the starter
What is the main purpose of all motor starter?
To start, stop and offer O/L protection
What is the main purpose of for overload protection in motor starter?
To protect the motor from excessive O/L current.
What does the term ‘maintained stop’ mean?
When pushed stays in the open/close state. Must be pulled back to original position.
What type of switch does not have to be horsepower rated?
Isolating switch. Doesn’t have to interrupt locked rotor current
What is the difference between a timed contact and an auxiliary contact on a on delay timer?
On a timer:
- Auxiliary contact closes the ?
- instant the coil is energized
- timed contact - times open or closed
What does DPDT mean?
Double-pole Double-throw
How do we wire stop buttons in a circuit? Start buttons?
- Stops in series
- starts in parallel
Do we ever have an opportunity to wire a coil in series?
No!
In parallel only.
What is the difference between low voltage protection (LVP) and low voltage release (LVR)
LVP: 3 Watts. Won’t restart during to seal-in contact.
LVR: X Watt
How many wires go to a simple stop start station?
3wires
