General Principles of Motor Control Flashcards
When installing a motor control system, List four major factors to consider concerning the power system.
Voltage Type of Load
HP of the Load
Amount of Inrush current when starting
Starting requirements of load
Where would you find motor information such as horsepower or voltage?
Motor Nameplate
Is the National Electric Code a law?
No, the NEC is only a recommendation included in the National Fire Protection Association (NFPA). It may be adopted as law in local jurisdictions
Explain Manual control
operator must go to the controller to operate the device, usually very simple systems
Explain Semiautomatic control
operator uses pushbuttons or other devices to control the operation of a magnetic contactor or starter that then controls the device, doesn’t have to be located near device
Explain Automatic control
After initial power-up, the system will operate on its own without operator control, the system will normally sense unsafe conditions and shut down on its own
What is Across-the-Line Starting?
Motor is connected directly to the power source, simplest starting method
Explain Jogging a motor
connecting a motor to full line voltage to move it to position, higher torque, more speed, less control
Explain Inching a motor
Connecting a motor to reduced voltage to move it to position, lower torque, less speed, greater control
What is the common way to control the speed of an AC motor?
Use a Variable Frequency Control (VFD) to change frequency of voltage supplied to the windings
What is the common way to control the speed of a DC motor?
Vary Voltage to field or armature windings
What is Ramping a motor?
Motor may start at a low speed and accelerate over time to the final speed, can also ramp down from high to low speeds
What is the most important function of any control system?
Protection of the operator and others in the vicinity of the machine through mechanical and electrical safeguards
List 4 basic functions of a motor control system
Starting Stopping Jogging/ Inching Speed Control Motor & Circuit Protection Surge Protection Safety
Name the devices used to protect the circuit
Fuses
Circuit breakers
