What is the definition of "trip time"?
The time it takes for a device to open a circuit in the event of an overload.

Learn more about trip time in the class Contactors and Motor Starters 250 below.

Motor Controls Training

Class Information
Tooling U-SME classes are offered at the beginner, intermediate, and advanced levels. The typical class consists of 12 to 25 lessons and will take approximately one hour to complete.
Class Name:Contactors and Motor Starters 250
Description:This class provides information on the basic design and function of contactors and motor starters. Includes an Interactive Lab.
Prerequisites: none
Number of Lessons:19
Language:English, Spanish
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Class Outline
  • Objectives
  • Elements of Motor Control
  • Relays and Contactors
  • Pros and Cons of Contactors
  • Manual Contactors and Magnetic Contactors
  • Contacts
  • Contact Arcing
  • Contact Bounce
  • Arc Suppression
  • Motor Overload Protection
  • Overload Relays
  • Thermal Overload Relays
  • Magnetic Overload Relays
  • Motor Starters
  • Across-the-Line Starters
  • Solid State, Primary Resistor, and Auto-Transformer Reduced Voltage Starters
  • Wye Delta and Part-Winding Reduced Voltage Starters
  • NEMA and IEC Standards and Ratings
  • Summary
Class Objectives
  • Describe primary components used for motor control.
  • Distinguish between relays and contactors.
  • List the pros and cons of contactors.
  • Distinguish between manual contactors and magnetic contactors.
  • Describe contacts.
  • Describe contact arcing.
  • Describe contact bounce.
  • Describe methods of arc suppression.
  • Define motor overload protection.
  • Describe overload relays.
  • Describe thermal overload relays.
  • Describe magnetic overload relays.
  • Describe motor starters.
  • Describe across the line motor starters.
  • Describe solid state, primary resistor, and auto-transformer reduced voltage motor starters.
  • Describe wye delta and part winding reduced voltage motor starters.
  • Distinguish between NEMA and IEC standards and ratings.

Class Vocabulary

Vocabulary TermDefinition
AC magnetic motor starter A type of starter for AC induction motors that combines a magnetic contactor and an overload relay. Magnetic motor starters can be operated remotely.
across-the-line starter A category of starters in which the motor is directly connected to the supply lines, allowing full voltage when the motor starts.
amperage A measurement that indicates the amount of current flowing in a circuit. Amperage is measured in amperes.
arc chute A method of arc suppression that extinguishes arcs by channeling them into chambers above the contacts.
arc column A string-like spark of electricity that connects across the gap between two contacts. Arc columns occur when electricity flows via ionized air molecules or vaporized metal and results in damage to the contacts.
arc suppression Any method used for extinguishing electrical arcs between contacts. Arc suppression is necessary to ensure worker safety and prolong contact life.
arcing The flow of electricity through the air from one conductor to another. Arcing can produce visible flashes and flames.
armature The part of a motor in which a current is induced by a magnetic field. The armature usually consists of a series of coils or groups of insulated conductors surrounding a core of iron.
auto-transformer A type of reduced voltage motor starter that uses a single-coil transformer to step voltage up or down.
bimetallic strip A strip made by bonding together two unlike metals that expand at different rates when heated. The different rates of expansion cause the bimetallic strip to curl.
bimetallic thermal overload relay A type of thermal overload mechanism that uses a strip composed of two different metals. When heated, the two metals expand at different rates, causing the strip to warp and create an opening in the circuit.
blowout coil A method of arc suppression that uses magnetic coils to create a magnetic field that pushes an arc upward until it breaks.
break The term for the number of places in which a circuit can be made or broken.
circuit breaker A safety device that detects overcurrent in a circuit. A circuit breaker often contains a bimetallic strip that bends and trips a switch that opens a circuit.
closed contact A point where two contacts connect with each other and allow current to flow, creating a circuit.
contact A conductive metal part in an electrical circuit that opens or closes the circuit by either separating from or touching a matching part.
contact bounce An unwanted effect that occurs when contacts close via high amounts of pressure and then rebound from each other due to the force. Contact bounce is undesirable because it can create secondary arcs and reduce contact life.
contact life The length of time the surface of a contact will remain in good working condition.
contactor A device that uses a small control current to energize or de-energize a load. Contactors can handle high amounts of current and are also combined with overload relays to create motor starters.
control component Any device that controls circuits, motors, and other electric or mechanical devices.
control relay An electrical switch that opens and closes a circuit. Relays can open or close one or many sets of contacts.
dashpot oil Oil that maintains viscosity over a wide range of temperatures. Dashpot oil is used in dashpot overload relays.
dashpot overload relay A type of overload relay in which a piston moves within a cylinder containing dashpot oil that is used to dampen and control motion.
de-ionizing Removing ions from a fluid or air and consequently prohibiting electrical conductivity. Ions are atoms that are electrically charged due to the loss or gain of one or more electrons.
delta A connection of three components where a triangular series circuit is formed. Delta connections are used in wye delta reduced voltage starters.
double-pole double-throw A set of 2 moveable contacts that can break a circuit in 2 places each.
double-pole single-throw A set of 2 moveable contacts that can break a circuit in 1 place each.
electronic overload relay A type of overload relay with a heaterless design that detects overload by monitoring motor current.
electronic reduced voltage starter A type of reduced voltage motor starter that is electronically controlled with no moving parts. Electronic reduced voltage starters regulate voltage to the motor in a series of small bursts of power until the motor reaches full power.
eutectic overload A type of thermal overload relay that uses a melting alloy to activate mechanical devices to open a circuit in the case of overload.
fuse A safety device that detects excess current in a circuit. Fuses often have a component that melts and opens the circuit.
heat sensitivity The ability of a device to detect heat.
IEC The International Electrotechnical Commission, which governs electrical equipment standards in Europe and all other international countries.
induction motor A commonly used industrial motor in which power is connected only to the stator. Alternating current in the stator induces current in the rotor and creates an electromagnetic field that produces rotation in the armature.
inrush current The initial surge of a current into a motor. Inrush current can be 12 times higher than current required for normal motor operation.
ionized Exhibiting a negative or positive charge after gaining or losing one or more electrons.
knife blade switch A lever-type switch that is used to control contactors.
magnetic contactor A type of contactor that is operated remotely through solenoid action.
magnetic overload relay A type of overload relay that is operated remotely through solenoid action.
magnetic relay A type of overload relay that senses the strength of the magnetic field that the current flow produces. Magnetic relays are often used in areas that experience extreme changes in temperature.
manual contactor A type of contactor that is operated by a person who activates a switch on the contactor.
manual controller An input device that requires a manual switch to control the flow of current in a circuit.
manual starter A type of starter that is operated by a person who activates a switch on the starter.
melting alloy overload relay A type of thermal overload relay that uses a melting alloy to activate mechanical devices to open a circuit in the case of overload.
motor overload protection The use of devices such as overload relays to open the circuit in the event of an overload to prevent the motor from overheating.
motor starter An electrically operated switch that uses magnetic induction to provide the startup current for a motor.
movable contact A contact on an armature that moves and connects to a matching stationary contact.
NEMA The National Electrical Manufacturers Association, which sets standards for equipment used in the United States.
normally closed Contacts that keep the circuit connected during normal operation and disconnect to open the circuit when the relay is activated.
open contact A contact that is separated with space between another matching contact, allowing no current to flow.
output device A device that performs a mechanical action after receiving the electrical signal to do so.
overcurrent Excess current. Devices like fuses and circuit breakers protect against overcurrent.
overload Excessive heating due to motor overcurrent and failure of motor to start.
overload relay A relay that is attached to a contactor in order to create a motor starter. Overload relays protect the motor from overload by disconnecting the power to the motor and stopping its operation.
part-winding starter A type of reduced voltage starter that applies power to only one set of windings, then to the other set as the motor comes up to speed.
pawl A hinged or pivoted device that fits into the notch of a ratchet, wheel, gear, or bar. A ratchet and pawl work together, either to produce forward motion or to prevent backward motion.
piston A rod inside a cylinder that is moved by hydraulic pressure.
pole The term for a set of moveable contacts that belong to a single circuit.
power relay A relay with heavy-duty contacts that is usually rated 15 amperes or higher. Power relays are also known as contactors.
primary resistor A type of reduced voltage starter that uses resistors to create an initial 30% drop in voltage before allowing full current to the motor.
ratchet wheel A toothed wheel that uses a bar called a pawl to keep it from turning in one direction.
reduced voltage starter A category of motor starters that reduce the power coming into the motor when it is initially started.
relay An electrical switch that opens and closes a circuit. Relays can open or close one or many sets of contacts.
resistor Am electronic component that regulates, limits, or opposes the flow of electrical current. Resistors tend to convert electrical energy into heat.
secondary arc An arc caused by contact bounce. The first arc is extinguished when contacts close, then a second arc is created when contacts bounce open again.
shaft A long cylindrical device such as a rod or pole.
silicon chip A miniature electronic circuit also known as an integrated circuit or microchip.
solder pot overload A type of thermal overload relay that uses a melting alloy to activate mechanical devices to open a circuit in the case of overload.
solenoid principle The use of a coil that enables voltage to convert electrical energy to mechanical energy via magnetic fields.
solid state Any device or system that functions by means of electronic components without the use of moving parts.
squirrel cage A type of three phase AC rotor that is constructed by connecting metal bars together at each end. It is the most common AC rotor type.
stationary contact A contact that remains in a fixed position during operation.
switch A control device that can make or break a circuit by closing or opening. A switch can be either manual, mechanical, or automatic.
tap An intermediate connection point on an electrical transformer.
thermal relay A type of overload relay that connects a heater with a motor. A thermal relay protects a motor by shutting it down if the relay detects excessive heat.
throw The term for the number of contacts that match the moveable contacts.
tip bar A mechanical part in a magnetic overload relay that tilts during overload and releases the support to a set of closed contacts, causing them to open and break the circuit.
trip time The time it takes for a device to open a circuit in the event of an overload.
viscosity A fluid's resistance to flow. Viscosity is used to describe friction of fluids.
warp To bend something that was formerly straight.
winding An electrically continuous length of insulated wire wound on a bobbin, spool, or form.
wye delta The configuration of motor windings in which windings form the shape of the letter Y, then a triangle shape called a delta.