Proper grounding practices protect people from the haz-ards of electric shock and ensure the correct operation of overcurrent protection devices. Intentional grounding is required for the safe operation of electrical…
Different types of electrical drawings are used in working with motors and their control circuits. In order to facilitate making and reading
Most industrial motors operate on voltages that range from 240 to 480 volts. Magnetic control systems, however, generally operate on 120 volts. A control transformer is used to step the…
Mercury relays employ the use of mercury-wetted contacts instead of mechanical contacts. Mercury relays contain one stationary contact called the electrode. The electrode is located inside the electrode chamber. When…
Motor starters are contactors with the addition of an overload relay. Because they are intended to control the operation of motors, motor starters are rated in horsepower. Magnetic motor starters…
Mechanically held contactors and relays are often referred to as latching contactors or relays. They employ two electromagnets to operate. One coil is generally called the latch coil and the…
Contactors are very similar to relays in that they are electromechanical devices. Contactors can be obtained with coils designed for use on higher voltages than most relays. Most relay coils…
The construction of the electromagnetic part of a relay or contactor greatly depends on whether it is to be oper ated by direct or alternating current. Relays and contactors that…
Relays are electromechanical switches that contain auxiliary contacts. Auxiliary contacts are small and are intended to be used for control applications. As ageneral rule, they are not intended to control…
Magnetic type overload relays operate by sensing the strength of the magnetic field produced by the current flow to the motor. The greatest difference between magnetic type and thermal type…