Motor Control Fundamentals Flashcards
Across-the-Line-Starters
Starting the motor across-the-line on full line voltage.
Auto-Transformer
The auto-transformer has a primary winding and a secondary winding in the form of one continuous winding. This winding is tapped at certain points to obtain the desired voltages.
Combination Starter
A disconnect with a short circuit protective device and a magnetic starter in one enclosure with the door mechanically interlocked so that it cannot be opened without first opening the disconnect.
In-Rush Current
At motor startup, the stator field cuts the rotor bars at a faster rate than when the rotor is turning.
Jogging
Opening and closing of a motor starting circuit to produce slight movements of the motor.
Magnetic Contactor
A contactor actuated electromagnetically.
Mechanical Interlock
Requires that the switch or breaker be in the off position before the door can be open.
Motor Control Center
Many combination starters may be clustered in a single cabinet or cubicle or several single cabinets into a single unit or area.
NEMA Size and Rating
The larger the number, the higher the current and horsepower rating.
Part Winding Starter
The stator windings of an induction machine are divided into two or more equal parts with all the terminals for each section available for external connection.
Plugging
A control function which provides braking by reversing the motor line voltage polarity or phase sequence so that the motor develops a counter-torque which exerts a retarding force.
Primary-Resistance Starter
Equal resistors are placed in series with each line at the instant the motor is started.
Reduced-Voltage Starters
The line voltage is reduced directly or indirectly in one or more steps for starting and acceleration up to full speed when full line voltage is applied for running the motor.
Secondary-Resistance on Wound Rotor Motor Starters
Control secondary current on start.
Thermal Relay
A relay that relies on the rising temperatures caused by the overload current.
Two-Wire Control
Two wires connect the control device (which could be a thermostat, float switch, limit switch, or other maintained contact device) to the magnetic starter.
Wye-Delta Starter
Changes the Delta motor connection to a Wye connection on start to take advantage of the series circuit characteristics of that configuration.
The source and in-line circuit supplies ___ to the conveyor drive motor.
electrical current
The circuit breaker is intended to…
protect in-line circuit conductors, control devices, motors and other load components from short circuits or grounds.
Energizing or deenergizing the coil of the motor starter causes the motor starter contacts to open or close, which causes the motor to either start or stop. True or false?
True
Motor overloads can only be electrical in origin. True or false?
False, motor overloads can be electrical as well as mechanical in origin.
Single phasing of a three-phase motor and low line voltage are examples of ___.
electrical overloads.
The conveyor drive train and the load carried by the conveyor are afforded jam protection by the ___.
jam relay
Terminal screws serve as convenient ___ for the troubleshooter.
test points
Checking phase voltages and currents can indicate the ___of a motor.
condition
Electrical Pigtail
A technique used to lengthen short wires or combine multiple wires together and leave one conductor that can connect to electrical devices.
volt-ohm-milliammeter (VOM)
digital multimeter (DMM)
No more than ___wires should be placed under any terminal screw or lug.
two
A voltage drop when across a set of contacts which are in the closed state indicates ___.
faulty contacts
