406 Electrical Power Systems Technology
Reduced-Voltage Starting
Control Relay
Safety Switch
Solenoid
Timing Relay
Switches
SPST
SPDT
DPST
DPDT
4-Way
3PST
3PDT
Rotary Switch
Limit Switch
Temperature Switch
Float Switch
Pressure Switch
Foot Switch
Pilot Lights
Full-Voltage
Transformer-Operated
Series Resistor
Illuminated Pushbutton
Combination Starter
Controller Enclosures-NEMA
POWER CONTROL STANDARDS, SYMBOLS, AND DEFINITIONS
A great amount of fundamental knowledge is needed in order to
fully understand electrical power control. Individuals who are concerned
with electrical power control systems should have a good knowledge of
the standards, symbols, and definitions that govern electrical power control.
NEMA Standards
The National Electrical Manufacturers’ Association (NEMA) has
developed standards for electrical control systems. NEMA standards are
used extensively to obtain information about the construction and per-