Download Single Line Diagram Symbols

Single Line Diagram Symbols
Non-Fusible Safety Switch (Non-Fused Switch)
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A switch with no associated fuses.
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Has no circuit protection capability.
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Provides a convenient means to open and close a circuit.
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Opening the circuit disconnects the load from its source of electrical power, while
closing the circuit connects the load.
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Circuit protection must be provided by external overcurrent devices such as circuit
breakers or fuses.
Fusible Safety Switch (Fused Switch)
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A safety switch that can be combined with fuses in a single enclosure.
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The switch provides a convenient means to manually open and close the circuit,
while the fuse provides overcurrent protection.
Fuse
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A type of sacrificial overcurrent protection device.
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The essential component is a metal wire or strip that melts when too much current
flows, which interrupts the circuit in which it is connected.
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Short circuit, overload or device failure is often the reason for excessive
current. A fuse interrupts excessive current (blows) so that further damage by
overheating or fire is prevented.
Tapped Coil (Coil Tap)
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A wiring feature found on some electrical transformers, inductors and coil pickups, all of
which are sets of wire coils.
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The coil tap(s) are points in a wire coil where a conductive patch has been exposed.
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When the coil taps are disconnected, the coil operates as normal.
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When a coil tap is connected to one end of the coil (or the end disconnected and
reconnected to the tap), the section of coil between the tap and its connected end is
bypassed - effectively reducing the number of turns in the coil.
Solenoid
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A coil wound into a tightly packed helix.
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In engineering, the term refers to a variety of transducer devices that convert energy into
linear motion.
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Solenoid valve An integrated device containing an electromechanical solenoid which
actuates either a pneumatic or hydraulic valve, or a solenoid switch, which is a specific type
of relay that internally uses an electromechanical solenoid to operate an electrical switch.
Inductor (Coil)
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A passive electrical component that can store energy in a magnetic field created by the
electric current passing through it.
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Typically a conducting wire shaped as a coil, the loops helping to create a strong magnetic
field inside the coil.
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One of the basic electronic components used in electronics where current and voltage
change with time, due to the ability of inductors to delay and reshape alternating currents.
Potentiometer
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A three-terminal resistor with a sliding contact that forms an adjustable voltage divider.
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Rarely used to directly control significant power (more than a watt), since the power
dissipated in the potentiometer would be comparable to the power in the controlled load.
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Instead they are used to control inputs for electronic circuits.
Time Delay Fuse (also known as anti-surge, or slow-blow)
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Fuse designed to allow a current which is above the rated value of the fuse to flow for a
short period of time without the fuse blowing.
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Used on equipment such as motors, which can draw larger than normal currents for up to
several seconds while coming up to speed.
Disconnect
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The part of the circuit that allows the technician to cut-off or interrupt the power supply.
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Typically contain fuses.
Wall Outlet
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Devices for removably connecting electrically operated devices to the power supply.
Terminal Connection
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Any part of the circuit where a component can be added, such as a relay or resistor.
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These can also be an area where branch circuits are spliced into the primary circuit.
Kill Switch
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Security measure used to shut off a device in an emergency situation in which it cannot be
shut down in the usual manner.
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Unlike a normal shut down, which shuts down all systems naturally and turns the machine
off without damaging it, a kill switch is designed to completely abort the operation at all
costs, and be configured so that it is quick to operate, and relatively obvious to someone
other than the usual operator.
45° Branch Circuit
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Part of a schematic that shows an additional wire or component branching off at a 45° angle.