CMPE 118 MECHATRONICS Solenoids, DC Motors And the fine art of Snubbing

CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS

Solenoids, DC Motors

And the fine art of Snubbing


Solenoids


Most Common Solenoid Types

Pull Push Open-Frame Rotary


Solenoid Characteristics


Design Affects Stroke vs. Force Characteristic


Typical Solenoid Specifications


DC Motors provide Rotary Motion

Where do you find them?



The Permanent Magnet DC Motor


Commutation


Electrical Model of a DC Motor


Deriving some useful relationships


More Room for Derivations


Torque vs. Speed Power vs. Torque


How Does P change with V at Constant T?


Where is PMAX and What is its Value?


Torque vs. Everything


DC Motor Specifications


Operating Ranges


Defining ‘Short Term Operation’


CMPE-118 DC Motor Lecture ProblemYou have been assigned to follow up on the design of a former employee who had not taken CMPE-118. Your supervisor suspects that they didn't know what they were doing. The only documentation that you can find shows that the motor chosen has Kt = 9.33 in.-oz./A and produces 2.8 in.-oz. at stall when driven at 12V. The design requires that the motor deliver 0.4 in.-oz. at 1500 rpm. The motor was supposed to be driven from a 12V supply and switched by a ULN2003. Your boss has asked you:

a) How can I find out how much current the motor will draw at stall ?

b) Can the ULN2003 safely switch the required current?

c) How can I find the NL Speed ?

d) How can I find the coil resistance ?

e) How can I find the torque at a given speed ?

f) Will the design meet the requirements for torque & speed? If not, what changes could you suggest?

g) To estimate the current required when running at the design point.

You may assume that there are no internal losses within the motor.KT = 1.3524KE [oz-in/A ; V/krpm]


Motor Design SolutionKt = 9.33 in.-oz./A Tstall = 2.8 in.-oz.Vstall = 12V. Treq = 0.4 in.-oz. req =1500 rpm. KT = 1.3524KE [oz-in/A ; V/krpm]


Directional ControlWith a Single Power Supply

The H-Bridge


Pulse Width Modulation


DC Motor Drive Simulation + V12V

E xt F ile

0 /0V2N 3055

1.2m H

50

11 .4


Drive Waveform

0 1 6 7 u 3 3 3 u 5 0 0 u 6 6 7 u 8 3 3 u 1 m- 2 0 0 m

7 0 0 m

1 . 6

2 . 5

3 . 4

4 . 3

5 . 2

R e f = G r o u n d X = 1 6 7 u S / D i v

Vol

ts


Transistor Current

0 1 6 7 u 3 3 3 u 5 0 0 u 6 6 7 u 8 3 3 u 1 m- 4 0 m

1 4 3 m

3 2 6 m

5 1 0 m

6 9 4 m

8 7 7 m

1 . 0 6


Cur

rent

(A

)


Inductor Current

0 167u 333u 500u 667u 833u 1m-1.06

-87 6m

-69 2m

-50 7m

-32 2m

-13 7m

47.2m

R ef=G ro und X= 16 7uS /D iv


Collector Voltage

0 16 7u 33 3u 50 0u 66 7u 83 3u 1 m

29 .4

68 .1

10 7

14 6

18 4

22 3

R e f= G ro un d X = 1 67 uS /D iv

0

Vol

ts


Diode Snubber+V

12V

E xt F ile

0 /0V 2N 3055

1.2m H DIO D E

50

11 .4


Collector Voltage w/ Diode Snubber

0 1 6 7 u 3 3 3 u 5 0 0 u 6 6 7 u 8 3 3 u 1 m- 4 7 9 m

1 . 8 2

4 . 1 3

6 . 4 3

8 . 7 4

1 1

1 3 . 3


Vol

ts


Inductor Current w/ Diode Snubber

0 1 6 7 u 3 3 3 u 5 0 0 u 6 6 7 u 8 3 3 u 1 m- 1 . 0 6

- 8 7 7 m

- 6 9 4 m

- 5 1 0 m

- 3 2 6 m

- 1 4 3 m

4 0 . 8 m


Cur

rent

(A)


How would we add diodesto protect the H-Bridge?


+V12V

E xt F ile

0 /0V 2N 3055

1.2m HDIO D E

ZE NE R

50

11 .4

Diode + Zener Diode Snubber


0 1 6 7 u 3 3 3 u 5 0 0 u 6 6 7 u 8 3 3 u 1 m- 1 . 5

5 . 4

1 2 . 3

1 9 . 2

2 6 . 1

3 3

3 9 . 9


Vo l

tag e

Collector Voltage with Diode + Zener Snubber


0 1 6 7 u 3 3 3 u 5 0 0 u 6 6 7 u 8 3 3 u 1 m- 1 . 0 6

- 8 7 7 m

- 6 9 3 m

- 5 0 9 m

- 3 2 5 m

- 1 4 1 m

4 2 . 5 m


Cur

r ent

Inductor Current with Diode + Zener Snubber


+V

Ext F ile

0/0V 2N3055

1.2m H

1N474950

11.4

Zener Only Snubber


0 1 6 7 u 3 3 3 u 5 0 0 u 6 6 7 u 8 3 3 u 1 m- 1 . 3 5

4 . 8 7

1 1 . 1

1 7 . 3

2 3 . 5

2 9 . 7

3 6


Vo l

tag e

Collector Voltage with Zener Only Snubber


3 0 3 u3 7 2 u 4 4 2 u 5 1 1 u 5 8 0 u 6 4 9 u 7 1 8 u- 1 . 0 6

- 8 7 5 m

- 6 9 0 m

- 5 0 6 m

- 3 2 1 m

- 1 3 7 m

4 7 . 6 m

R e f = G r o u n d X = 6 9 . 2 u S / D i v 2 4 1 %

Cur

r ent

Inductor Current Decay Comparison

Diode Only

Resistor + Diode

Diode + Zener

Zener Only

No Snubber


How would we add Zener diodesto protect the H-Bridge?


The Brushless DC Motor


Commutating a Brushless DC Motor


Hall Sensor Based Commutation


Brushed vs. Brushless DC Motors

Brushed Motor Brushless Motor

Mechanical Structure Field Magnets on statorWindings on Rotor

Field Magnets on RotorWindings on stator

Commutation MethodMechanical contact betweenbrushes and commutatoradded friction, brush debris,RFI

Electronic switching using transistorslow frequency harmonics due to ripple

Rotor Position Detection Automatically detected bybrushes

Hall Element, optical encoder, BackEMF

Reversing Method Reverse terminal voltage Rearrange logic sequencer

Distinctive FeaturesQuick responseExcellent controllabilityCurrent limited bybrush/commutator interfaceSpeed limited by brush bounce

Long LastingEasy or no maintenanceCurrent limited by winding resistanceonlyNo fundamental high frequency(speed) limitUsually more efficient than brushed


0 1 6 7 u 3 3 3 u 5 0 0 u 6 6 7 u 8 3 3 u 1 m- 1 . 0 6

- 8 7 7 m

- 6 9 4 m

- 5 1 0 m

- 3 2 6 m

- 1 4 3 m

4 1 m


Cur

r ent

Inductor Current with Zener Only Snubber

Documents

CMPE 118 MECHATRONICS Solenoids, DC Motors And the fine art of Snubbing