Post on 20-Dec-2015
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
Solenoids, DC Motors
And the fine art of Snubbing
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
Solenoids
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
Most Common Solenoid Types
Pull Push Open-Frame Rotary
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Solenoid Characteristics
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Design Affects Stroke vs. Force Characteristic
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Typical Solenoid Specifications
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DC Motors provide Rotary Motion
Where do you find them?
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CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
The Permanent Magnet DC Motor
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Commutation
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Electrical Model of a DC Motor
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Deriving some useful relationships
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More Room for Derivations
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Torque vs. Speed Power vs. Torque
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How Does P change with V at Constant T?
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Where is PMAX and What is its Value?
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Torque vs. Everything
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DC Motor Specifications
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Operating Ranges
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Defining ‘Short Term Operation’
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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]
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
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]
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Directional ControlWith a Single Power Supply
The H-Bridge
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Pulse Width Modulation
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DC Motor Drive Simulation + V12V
E xt F ile
0 /0V2N 3055
1.2m H
50
11 .4
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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
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
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
R e f = G r o u n d X = 1 6 7 u S / D i v
Cur
rent
(A
)
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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
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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
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Diode Snubber+V
12V
E xt F ile
0 /0V 2N 3055
1.2m H DIO D E
50
11 .4
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
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
R e f = G r o u n d X = 1 6 7 u S / D i v
Vol
ts
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
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
R e f = G r o u n d X = 1 6 7 u S / D i v
Cur
rent
(A)
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How would we add diodesto protect the H-Bridge?
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+V12V
E xt F ile
0 /0V 2N 3055
1.2m HDIO D E
ZE NE R
50
11 .4
Diode + Zener Diode Snubber
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
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
R e f = G r o u n d X = 1 6 7 u S / D i v
Vo l
tag e
Collector Voltage with Diode + Zener Snubber
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
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
R e f = G r o u n d X = 1 6 7 u S / D i v
Cur
r ent
Inductor Current with Diode + Zener Snubber
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
+V
Ext F ile
0/0V 2N3055
1.2m H
1N474950
11.4
Zener Only Snubber
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
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
R e f = G r o u n d X = 1 6 7 u S / D i v
Vo l
tag e
Collector Voltage with Zener Only Snubber
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
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
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
How would we add Zener diodesto protect the H-Bridge?
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The Brushless DC Motor
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Commutating a Brushless DC Motor
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Hall Sensor Based Commutation
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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
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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
R e f = G r o u n d X = 1 6 7 u S / D i v
Cur
r ent
Inductor Current with Zener Only Snubber