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.
