- Difinition of Motor.
- Discuss the type of motors
- Describe the parts of a motor
- Define the use of Motor Controllers
- Discuss the type of Motor Controllers
- electrical machine that converts electrical energy into mechanical energy.
-motors operate through the interaction between an electric motor's magnetic field and winding currents to generate force within the motor.
_ motors can be powered by AC voltage or DC voltage.
Parts of a motor
How it works?
- Almost all motor in the Navy are:
-Polyphase induction motors have a primary winding (usually the stator winding) which is connected to the power supply, and a secondary winding (usually the rotor winding) which has no electrical connection to the power supply. Currents in the primary winding set up a rotating magnetic ﬁeld. The rotating magnetic ﬁeld induces voltages and currents in the secondary winding, and gives rise to a mechanical force which turns the rotor.
-Most motor are single speed, but however for some application, multi speed and variable speed are possible through:
-Squirrel cage induction motor
-Wound-Rotor induction motor
AC Motors cont...
- SQUIRREL CAGE INDUCTION MOTORS
-it has a rotor winding made of longitudinal bars in slots just below the outer surface of the rotor. The bars are connected to and short circuited by rings at the ends of the rotor. The rotor winding may be of individual bars and rings of conducting material connected together, or it may be a one-piece structure made by die casting the rings and bars together. In the diecast construction, the fan blades for cooling the motor are frequently cast in one piece with the rotor winding.
AC motors cont...
- WOUND-ROTOR INDUCTION MOTORS
-The wound-rotor induction motor is similar to the squirrel cage motor except that the rotor winding is made of individually insulated coils. Connections from the coils are brought to collector rings. The rotor circuit is not short circuited on itself as in the squirrel cage motor, but is completed through external resistors connected to brushes which bear on the collector rings. Motor speed, starting current, and other characteristics can be adjusted by varying the external resistors
AC motors cont...
-SYNCHRONOUS SPEED AND SLIP.
The speed of rotation of the rotating magnetic ﬁeld is known as the synchronous speed. The rotor of an induction motor runs at somewhat less than synchronous speed. The difference between synchronous speed and rotor speed is known as the slip. Synchronous speed (revolutions per minute) is 120 times the frequency of the power supply (Hz) divided by the number of poles in the primary winding.
-Motors that are powered by DC voltage.
-Stabilized Shunt Motor
These motors have ﬁeld coils connected in parallel with the armature. Shunt motors are used in applications which require only moderate starting torque and a speed which is substantially unaffected by changes in load.
Series motors have ﬁeld coils connected in series with the armature. The speed of a series motor varies widely with load and may be excessive at no load. Series motors are limited to applications where the load is directly connected and change in speed with load is desirable, or can be tolerated. Series motors provide high starting torque.
Compound motors have one set of ﬁeld coils connected in parallel with the armature and another set connected in series with the armature. These shunt and series ﬁeld coils are proportioned to give the desired compromise between the characteristics of shunt and series motors.
Stabilized Shunt Motors.
These motors are similar to compound motors except that the series ﬁeld coils are of relatively low strength. Without the stabilizing series ﬁeld, some shunt motors would increase in speed with an increase in load.
- is a device or group of devices which serves to govern, in some predetermined manner, the operation of the motor to which it is connected.
Types of controllers:
Low Voltage Protection (LVP)
Low voltage (or under voltage) protection is the feature which provides for disconnecting the motor from the power supply upon reduction or loss of voltage; and keeping it disconnected after voltage returns until the operator restarts the motor.
Low Voltage Release (LVR)
Low voltage (or under voltage) release is the feature which provides for disconnecting the motor from the power supply upon reduction or loss of voltage and for keeping it disconnected until power returns; and then automatically reconnecting the motor to the power line to restart it.
Low Voltage Release Effect (LVRE)
Low voltage (or under voltage) release effect is the feature which provides the same effect in manual controllers as is obtainable in low voltage release type magnetic controllers. This is accomplished by leaving the motor connected to the power supply upon reduction or loss of voltage; and permitting the motor to restart upon restoration of voltage.
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Public - 9/13/16, 1:35 AM