216 Unit 2 Dc Motors 2

Front 1

A DC motor develops its base speed when full voltage is applied to its _______ and _______.

Back 1

armature and shunt field

Front 2

To reduce the speed of the motor, voltage is reduced to the _______, while maintaining full voltage at the _____

.

Back 2

armature, field

Front 3

There are several methods used to reduce speed of the motor

Back 3

1: Series Resistors 2: Separate Power Supplies

Front 4

The most common method of speed control for DC motors is the use of either a manual or motor drive controlled variable voltage supply. This method provides smooth speed control from 0 rpm- Base Speed rpm, and in the case of drives, can be arranged to provide feedback about motor operating conditions.

Back 4

No Answer

Front 5

A DC motor can be driven to speeds over its rated base speed by

Back 5

maintaining full voltage to the armature, and reducing current flow through the shunt field.

Front 6

A shunt field rheostat is connected in series with the shunt field winding to

Back 6

limit current flow.

Front 7

With less CEMF in the armature,current flow _______. As current flow _____, a net gain in torque occurs, ________ speed.

Back 7

increases, increases, increases

Front 8

Horse Power Equation

Back 8

HP = (1.59 x T x RPM) / 100,000 T = Torque RPM = Speed 1.59 & 100,000 = Constants

Front 9

1 HP = ___ W

Back 9

746w

Front 10

The armature is constructed using permanent magnets, and therefor, does not have a

Back 10

commutator, armature windings, or brushes.

Hint 10

Brushless motors

Front 11

A _________ is required to change the applied DC into three- phase AC.

Back 11

converter (inverter)

Front 12

Typical converters for brushless motor produce an AC waveform referred as a

Back 12

trapazoidal wave.

Front 13

This waveform can produce about __% more torque than a regular sine wave, but is not as smooth and results in ________ at low speeds.

Back 13

10%, torque ripple

Front 14

RPM Equation

Back 14

RPM = (120 x f) / #Poles

Front 15

Inside-Out motors, are constructed in a way that the moving component surrounds the stationary component. This design is capable of excellent _______ regulation due to the high inertia of the flywheel-like design. Commonly used for fans and blowers in high-speed HAVC equipment.

Back 15

speed

Front 16

Brushless motor Advantages

Back 16

Motor components are less expensive due to armature design. -Require less maintenance and downtime than brush-type motors. -Better heat dissipation characteristics than wound armature type DC motors.

Front 17

Disadvantage of Brushless Motor

Back 17

Cost of converter/electronics mitigates less expensive motor components (brushless $ ≈ brush-type $)

Front 18

A ________ differs from conventional DC motors by using permanent magnet pole pieces in place of wound electromagnets. Due to improvements in the magnetic materials used for the pole pieces, the HP rating of these motors have increased (~15HP). Despite the small horsepower ratings of these motors, they are generally more efficient than their conventional DC motor counterparts. Additionally, their weight-to-torque ratios and power-to-weight ratios can be up to (respectively) greater than conventional DC motors.

Back 18

permanent magnet, 90% and 200%

Front 19

Brushless motor that has very low inertia, can be operated at high speeds, and can be stopped and reversed quickly.

Back 19

Servomotor

Front 20

A kind of servomotor where the armature is constructed from several layers of copper conductors on a fiberglass disc.

Back 20

Servodisc motor

Front 21

What motor uses Permanent magnets arranged on both sides of the armature to create an alternating magnetic field.

Back 21

Permanent magnet motor

Front 22

Permanent Magnet Motors generally have good ________ to weight ratio.

Back 22

Torque

Front 23

-Avoid the problem of cogging at low speeds. -Feature extremely high acceleration (0-3000 RPM in 1/6 rotation.) -High operating speeds (up to 4000 RPM). -Very small design profile.

Back 23

Servodisc motors