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motion control > lesson 3-5 > Flashcards

lesson 3-5 Flashcards

1
Q

the rotating part of the motor

A

armature

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2
Q

It is constructed from an iron cylinder that has slots cut into it. Wire is wound through the slots to form the windings. The ends of the windings are connected to the commutator, which consists of insulated copper bars and is mounted on the same shaft as the windings.
The windings and commutator together form the ______

A

armature

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3
Q

is the winding (or set of windings) of anelectric machine

A

armature

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4
Q

Types of DC Servo motor

A

Permanent Magnet
Series
Shunt
Compound

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5
Q

usesa magnet to supply field flux. ____________ DC motors have excellent starting torque capability with good speed regulation. A disadvantage of _________ DC motors is they are limited to the amount of load they can drive. These motors can be found on low horsepower applications.

Another disadvantage is that torque is usually limitedto 150% of rated torqueto prevent demagnetization of the ____________.

A

Permanent Magnet DC Motors

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6
Q

motor the field is connected in series with the armature.The field is wound with a few turns of large wire because it must carry the full armature current.

A

series DC motor

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7
Q

the motor develops alarge amount of starting torque. However, speed varies widely between no load and full load. Series motors cannot be used where a constant speed is required under varying loads.

A

series motors

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8
Q

generally are not suitable for use on most variable speed drive applications.

A

Series-connected motors

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9
Q

motor the field is connected in parallel with the armature windings. The ___________ motor offers good speed regulation. The field winding can be separately excited or connected to the same source as the armature.

The advantage to a separately excited _______ field is the ability of a variable speed drive to provide independent control of the armature and field

A

Shunt motors

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10
Q

the supply is given separately to the field and armature windings. The main distinguishing fact in these types of DC motor is that, the armature current does not flow through the field windings, as the field winding is energized from a separate external source of DC current.

A

Separately excited

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11
Q

have a field connected in series with the armature and a separately excited shunt field.

The series field providesbetter starting torqueand the shunt field providesbetter speed regulation.

A

Compound motors

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12
Q

A type of servomotor that uses AC electrical input in order to produce mechanical output in the form of precise angular velocity is known as __________.

A

AC SERVOMOTOR

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13
Q

servomotors are basically two-phase induction motors with certain exceptions in designing features.

A

AC SERVOMOTOR

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14
Q

The output power achieved from ac servomotor ranges between some

A

watt to a few hundred watts

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15
Q

AC Servo motor the operating frequency range is between

A

50 to 400 Hz

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16
Q

are basically two-phase squirrel cage induction motors and are used for low power applications. Nowadays, three phase squirrel cage induction motors have been modified such that they can be used in high power servo systems.

A

AC SERVOMOTOR

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17
Q

The main difference between a standard split-phase induction motor and AC motor

A

is that the squirrel cage rotor of a servo motor has made with thinner conducting bars, so that the motor resistance is higher.

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18
Q

two distinct types of AC servo motors

A
  1. SYNCHRONOUS-TYPE AC SERVO MOTOR
  2. INDUCTION-TYPE AC SERVO MOTOR
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19
Q

consist of stator and rotor. The stator consists of a cylindrical frame and stator core. The armature coil wound around the stator core and the coil end is connected to with a lead wire through which current is provided to the motor.

A

SYNCHRONOUS-TYPE AC SERVO MOTOR

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20
Q

The rotor consists of a permanent magnet and hence they do not rely on AC induction type rotor that has current induced into it. also called as brushless servo motors because of structural characteristics.

A

SYNCHRONOUS-TYPE AC SERVO MOTOR

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21
Q

When the stator field is excited, the rotor follows the rotating magnetic field of the stator at the synchronous speed. If the stator field stops, the rotor also stops. With this permanent magnet rotor, no rotor current is needed and hence less heat is produced.

A

SYNCHRONOUS-TYPE AC SERVO MOTOR

22
Q

Also, these motors have high efficiency due to the absence of rotor current. In order to know the position of rotor with respect to stator, an encoder is placed on the rotor and it acts as a feedback to the motor controller.

A

SYNCHRONOUS-TYPE AC SERVO MOTOR

23
Q

structure is identical with that of general motor. In this motor, stator consists of stator core, armature winding and lead wire, while rotor consists of shaft and the rotor core that built with a conductor as similar to squirrel cage rotor.

A

INDUCTION-TYPE AC SERVO MOTOR

24
Q

The working principle of this servo motor is similar to the normal induction motor. The controller must know the exact position of the rotor using encoder for precise speed and position control.

A

INDUCTION-TYPE AC SERVO MOTOR

25
Q

The controller must know the exact position of the rotor using encoder for precise speed and position control.

A

3 PHASE AC SERVO MOTOR

26
Q

It is mainly composed of two major units, stator and rotor.

A

AC SERVO MOTOR
WORKING PRINCIPLE

27
Q

motor consists of two separate windings uniformly distributed and separated at 90°, in space. Out of the two windings, one is referred as main or fixed winding while the other one is called control winding.

A constant ac signal as input is provided to the main winding of the stator. However, as the name suggests, the control winding is provided with the variable control voltage. This variable control voltage is obtained from the servo amplifier.

A

The stator of ac servo

28
Q

two windings of stator of ac servo motor

A

main or fixed winding
called control winding.

29
Q

is generally of two types; one is squirrel cage type while the other is drag cup type

A

Rotor

30
Q

The rotor is generally of two types

A

squirrel cage
drag cup type

31
Q

In this type of rotor, the length is large while the diameter is small and is constructed with aluminium conductors thus weighs less.

It is to be noted here that the torque-speed characteristics of a normal induction motor have both positive as well as negative slope regions that represent unstable and stable regions, respectively.

A

squirrel cage

32
Q

are designed to possess high stability thus, its torque-slip characteristics must not have a positive slip region. Along with this the torque developed in the motor must reduce in a linear manner with speed.

A

AC SERVO MOTOR
PARTS

33
Q

This type of rotor is different in construction from that of squirrel cage one. It consists of a laminated core of aluminium around which drag cup is present with certain air gaps on both the side.

A

drag cups

34
Q

are attached with a driving shaft that facilitates its operation.

A

drag cups

35
Q

The two air gaps in both sides of the core lead to reducing the inertia thus is used in applications where there is a low power requirement.

A

drag cups type

36
Q

Initially, a constant ac voltage is provided at the main winding of the stator of the ac servomotor. The other stator terminal of the servomotor is connected to the control transformer through the control winding.

A

WORKING PRINCIPLE

37
Q

APPLICATIONS OF AC SERVOMOTORS

A

Due to the various advantages offered by the AC servomotors, these majorly finds applications in the instruments that operate on servomechanism, in position controlling devices, computers. Along with this these also find applications in tracking systems, machine tools and robotics machinery.

38
Q

is an electric motor whose main feature is that its shaft rotates by performing steps, that is, by moving by a fixed amount of degrees. This feature is obtained thanks to the internal structure of the motor, and allows to know the exact angular position of the shaft by simply counting how may steps have been performed, with no need for a sensor. This feature also makes it fit for a wide range of applications.

A

STEPPER MOTOR

39
Q

stepper motor parts

A

rotor
stator
shaft
phase A
phase B
phase C
phase D
phase E
Front endcap
bearing
winding
rear endcap
magnet
rotor section

40
Q

STEPPER MOTOR WORKING PRINCIPLES

A

As all with electric motors, stepper motors have a stationary part (the stator) and a moving part (the rotor). On the stator, there are teeth on which coils are wired, while the rotor is either a permanent magnet or a variable reluctance iron core. We will dive deeper into the different rotor structures later.

41
Q

The basic working principle of the stepper motor is the following:

A

By energizing one or more of the stator phases, a magnetic field is generated by the current flowing in the coil and the rotor aligns with this field. By supplying different phases in sequence, the rotor can be rotated by a specific amount to reach the desired final position.

42
Q

control how a stepper motor operates

A

Stepper drives

43
Q

there are three commonly used excitation modes for stepper motors

A

full step, half step and microstepping

44
Q

converts electronic signals into mechanical movement each time an incoming pulse is applied to the motor.

A

stepper motor

45
Q

If the stepper motor has a 1.8° step resolution, then in order for shaft to rotate one complete revolution, in full step operation, the stepper motor would need to receive 200 pulses, 360° ÷ 1.8 = 200.

A

okay

46
Q

the motor is operated with only one phase energized at a time. This mode requires the least amount of power from the driver of any of the excitation modes.

A

One-phase on - full step
FULL STEP EXCITATION MODES

47
Q

the motor is operated with both phases energized at the same time. This mode provides improved torque and speed performance. _________on provides about 30% to 40% more torque than one phase on, however it requires twice as much power from the driver.

A

Two-phase on - full step

48
Q

mode is a combination of one phase on and two phase on full step modes. This results in half the basic step angle. This smaller step angle provides smoother operation due the increased resolution of the angle.

A

Half step excitation mode

49
Q

produces about 15% less torque than two phase on - full step, however modified _______ eliminates the torque decrease by increasing the current applied to the motor when a single phase is energized.

A

Half step

50
Q

can divide a motor’s basic step by up to 256 times, making small steps smaller. A Micro drive uses two current sinewaves 90° apart, this is perfect for enabling smooth running of the motor. You will notice that the motor runs is quietly and with no real detectable stepping action.

A

Microstepping

51
Q

By controlling direction and amplitude of the current flow in each winding, the resolution increases and the characteristics of the motor improve, giving less vibration and smoother operation. Because the sinewaves work together there is a smooth transition from one winding to the other. When current increases in one it decreases in the other resulting in a smooth step progression and maintained torque output.

A

MICROSTEPPING

52
Q
A

motion control (1 decks)

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