What is low voltage release?
a control circuit feature that automatically restarts electrical equipment (like fans or pumps) once power is restored following an outage.
What is low voltage protection
a safety feature in electrical circuits that shuts down equipment during a power drop and, crucially, prevents it from automatically restarting when power returns
What are the four basic types of drawings used in equipment design?
- Block
- Wiring
- Schematic
- Interconnection
What provides an overview of components rather than specific construction and wiring details.
Block diagram
What diagram shows the detailed wiring of control devices and equipment
the physical position of the components.
Wiring diagram
What do interconnection diagrams often display alongside terminal numbers?
- Identification of associated conductors
- By number, letter, or colour
This helps facilitate the installation of complex wiring systems.
What does a schematic diagram demonstrate?
- Also called a ladder or elementary diagram.
- sequence of operation.
- The location of the equipment is not tepresented
- Useful for trouble shooting
- used for complex circuits
What are the 3 basic sections of a stop start control circuit for a motor?
Stop circuit
Start circuit
Holding circuit
What are interlock contacts?
They are contacts in a circuit that enable an operation to take place or prevent one from taking place.
What are the 4 types of motor control?
2 wire manual control
2 wire automatic control
3 wire manual control
3 wire automatic control
Pilot lights are connected in ___ with the operating coil and in ___ with contacts
Parallel
Series
What diagram shows specific connection details
- no function or physical location represented
Interconnection diagram
What can a pin out diagram also be considered?
An interconnection diagram
How are automatic pilot devices and contacts represented on control schematics?
As if systems are empty and de-energized
Holding contacts should be in series with the contactor coil?
True or false?
True
A basic reversing motor magnetic starter would consist of:
2 contactors and one overload relay
To achieve jogging what must happen?
The holding contacts must be open
Modern vfds provide jogging and inching control?
True or false?
True
A continuity test is made on a reversing motor magnetic starter between NEMA terminals 3 and 5, the reading of the ohmmeter is between 200 and 500 ohms. This would be an acceptable reading.
True or false?
True
When a motor magnetic starter is to be used to supply a motor that is to be jogged, the hp rating of the motor starter would be reduced.
True or false
True
To be able to go directly from FORWARD to REVERSE. the normally closed contacts of the reverse start button should be connected in the:?
Forward start circuit
The main purpose of the electrical interlocks on a reversing motor is to?
Prevent coil burn out
The purpose of “iogging” is to:
Energize motors for a short duration
Start circuit interlock contacts.
Contacts connected in the start circuit impact what?
Only the starting of the motor
