Drum switch are not motor starters because they do not contain ___
. … Although the power circuit and control circuit operate together to control a motor, they are electrically isolated from each other through a ___. Limit. ___ switches may be used to provide automatic control of reversing circuits.
What is a drum switch used for?
One of the most commonly used switches for
motor control
is the drum switch (Fig. 5-1). It has the capability to reverse a motor or turn it off. Drum switches may be used for across-the-line starting and the reversing of ac poly-phase, ac single-phase, or dc motors.
How does a drum switch work?
The drum switch is a manual switch that
lets one manually reverse the direction in which a motor is turning
. The switch contacts are open and closed manually by moving the drum switch from the off position to the forward or reverse position.
Do Drum switches provide overload protection?
When used to control single-phase motors, they are typically rated up to 3 horsepower at 240V or 1.5 horsepower at 120V.
The drum switch does not provide overload protection
.
Can the drum switch be used to reverse a three phase motor?
When used as a drum switch in a reversing drum switch application the
ASI
motor switch can be used with single phase and 3 phase motors, depending on the model selected.
What is a limit switch used for?
In electrical engineering, a limit switch is a switch operated by the motion of a machine part or the presence of an object. A limit switch can be used for
controlling machinery as part of a control system
, as a safety interlock, or as a counter enumerating objects passing a point.
What is a toggle switch?
A toggle switch is
a type of electrical switch that is actuated by moving a lever back and forth to open or close an electrical circuit
. … A maintained switch changes its position when actuated and will remain in that position until actuated again, such as an ON/OFF function.
What are the two parts of a motor schematic?
The AC motor consists of two main parts:
the rotor and the stator
. The stator is the outer shell and remains stationary. It has windings that transform the incoming electricity into a magnetic field. This causes the rotor to become magnetized in the opposite polarity and repel and rotate.
What type of device can be used to reverse the direction of a motor?
A commutator
is a device which is used to reverse the direction of current in the coil of a motor.
How do you change the rotation of an electric motor?
This happens to be an easy fix: all you need to do is
swap any two the power leads to flip/reverse the magnetic field
, and the most common practice is to switch lines 1 and 3. Once this is done, the motor should be running in the right direction. If you have more than 3 leads, it may take a bit more.
Which of the following can provide motor overload protection but have the disadvantage of being nonrenewable?
Dual-element or time- delay fuses
can provide motor overload protection but suffer the disadvantage of being nonrenewable and must be replaced.
Do contactors have overload protection?
Contactors are used to control power in a variety of applications. When applied in motor-control applications, contactors can only start and stop motors. Contactors cannot sense when the motor is being loaded beyond its rated conditions.
They provide no overload protection
.
How may an automatic operation be achieved when a manual motor starter is used?
Because manual starters are hand-operated mechanical devices (requiring no electrical coil), the contacts remain closed and the lever stays in the ON position in the event of a power failure. As a result, the
motor automatically restarts when the power returns
.
How many contractors are necessary for reversing starters?
To do this,
two contactors
for the starter assembly are required-one for the forward direction and one for the reverse direction, ill. 3. A technique called interlocking is used to prevent the contactors from being energized simultaneously or closing together and causing a short circuit.
How is forward and reverse motor connected?
Reversing Magnetic Starters
When the forward contactor is energized, power contacts connect line L1 to T1, line L2 to T2 and line L3 to T3 at the motor. When the reverse contactor is energized, the power contacts
connect line L1 to T3, line L2 to T2 and line L3 to T1
at the motor.
