PS Basics of a DC Drive
Transcript of PS Basics of a DC Drive
-
7/29/2019 PS Basics of a DC Drive
1/37
DC DRIVE BASICS
-
7/29/2019 PS Basics of a DC Drive
2/37
Purpose of a DC Drive
Alternating
Voltage
V
T
T
V
Direct Voltage
A DC drive converts AC power to DC voltage
in order to vary the speed and torque of the motor
-
7/29/2019 PS Basics of a DC Drive
3/37
DC Motor Review
Speed is primarily determined by Armature Voltage
Torque is determined by Armature Current
-
7/29/2019 PS Basics of a DC Drive
4/37
DC Motor Review
Rotation is the result of two independent electromagnetic
fields.
Armature windings
Field windings
Extended motor speeds above base speed are achieved
by reducing the field voltage (current)
Field Weakening
-
7/29/2019 PS Basics of a DC Drive
5/37
DC Drive
Shunt
Field
M
Field Supply
3 Phase AC
Power
SCR
Gate
DC Armature
T1 T3 T5
T2 T4 T6
L1L2
L3
+
-
Firing Circuit
Regulator
Operator
Control Station
Current
Feedback
Voltage
Feedback
-
7/29/2019 PS Basics of a DC Drive
6/37
DC Drive Components
Shunt
Field
M
Field Supply
3 Phase AC
Power
SCR
Gate
DC Armature
T1 T3 T5
T2 T4 T6
L1L2
L3
+
-
Firing Circuit
Regulator
Operator
Control Station
Current
Feedback
Voltage
Feedback
DC DRIVE
INPUT
Alternating
Voltage
V
T
-
7/29/2019 PS Basics of a DC Drive
7/37
Shunt
Field
M
Field Supply
3 Phase AC
Power
SCR
Gate
DC Armature
T1 T3 T5
T2 T4 T6
L1L2
L3
+
-
DC Drive Components
Firing Circuit
Regulator
Operator
Control Station
Current
Feedback
Voltage
Feedback
SiliconControl
Rectifiers
(SCR)
Permits current to flow in 1 direction
Gate signals when conduction occurs
T
V
Direct Voltage
-
7/29/2019 PS Basics of a DC Drive
8/37
Shunt
Field
M
Field Supply
3 Phase AC
Power
SCR
Gate
DC Armature
T1 T3 T5
T2 T4 T6
L1L2
L3
+
-
DC Drive Components
Firing Circuit
Regulator
Operator
Control Station
Current
Feedback
Voltage
Feedback
Field Supply
Used to Control
Field Voltage/Current
-
7/29/2019 PS Basics of a DC Drive
9/37
Shunt
Field
M
Field Supply
3 Phase AC
Power
SCR
Gate
DC Armature
T1 T3 T5
T2 T4 T6
L1L2
L3
+
-
DC Drive Components
Firing Circuit
Regulator
Operator
Control Station
Current
Feedback
Voltage
Feedback
Operator ControlStation
Sends Instructions
to Regulator
-
7/29/2019 PS Basics of a DC Drive
10/37
Shunt
Field
M
Field Supply
3 Phase AC
Power
SCR
Gate
DC Armature
T1 T3 T5
T2 T4 T6
L1L2
L3
+
-
DC Drive Components
Firing Circuit
Regulator
Operator
Control Station
Current
Feedback
Voltage
Feedback
Regulator
Compares instructions
feedback signals and
send appropriate signal to
firing circuit
Current (Torque)
Voltage (Speed)
-
7/29/2019 PS Basics of a DC Drive
11/37
Shunt
Field
M
Field Supply
3 Phase AC
Power
SCR
Gate
DC Armature
T1 T3 T5
T2 T4 T6
L1L2
L3
+
-
DC Drive Components
Firing Circuit
Regulator
Operator
Control Station
Current
Feedback
Voltage
Feedback
Firing Circuit
Supplies the gate pulses
that fire the SCRs
-
7/29/2019 PS Basics of a DC Drive
12/37
Speed Power Curve
Armature Voltage Control
Constant Field Current
Field Current Control
Constant Armature
Voltage
Constant Power
Con
stantT
orque
Speed (% of Base Speed)
Power(%o
fRated)
100
100
-
7/29/2019 PS Basics of a DC Drive
13/37
Speed Torque Curve
-
7/29/2019 PS Basics of a DC Drive
14/37
Forms of Stopping
Coast to Rest
Ramp Stop
Dynamic Braking
Regeneration
-
7/29/2019 PS Basics of a DC Drive
15/37
Dynamic Braking Dynamic Braking
- Dissipates rotating mechanical energy to heat
- Faster than coasting to rest
- Not Controllable (except by changing the resistor)
Firing Circuit
Regulator
Operator Control
Station
Current
Feedback
Voltage
Feedback
M
Foward
Current
DB
Resistor
Drive Powering Motor
M
Foward
Current
Dynamic
Braking
Resistor
Stop Signal
Sent
DynamicBraking
Current
-
7/29/2019 PS Basics of a DC Drive
16/37
Regeneration Regeneration
- Occurs when load overhaul motor
- Puts power back into drive through 2nd set of
SCRs
M
Forward Reverse Foward
Current
Reverse
Current
Firing Circuit
Regulator
Operator Control
Station
Current
Feedback
Voltage
Feedback
Benefits
- Stop High Inertia Loads Faster
- Return Energy to AC Power Line
-
7/29/2019 PS Basics of a DC Drive
17/37
Stopping Time
CoastStop
Ramp
Stop
Dynamic
Braking
RegenerativeBraking
-
7/29/2019 PS Basics of a DC Drive
18/37
Speed Regulation
How Much Will the Speed Change
Between No Load and Full Load?
Expressed as a Percentage
of Base Speed
-
7/29/2019 PS Basics of a DC Drive
19/37
-
7/29/2019 PS Basics of a DC Drive
20/37
Speed Regulation
-
7/29/2019 PS Basics of a DC Drive
21/37
Feedback Options
Speed Feedback Type Regulation
Voltage - 2 %
AC Tachometer RE O45 1 %
DC Tachometer 5PY 1 %
Encoder (pulse) RD-120-1 .01%
Encoder (pulse) RL - 1024 .01 %
Feedback device can determine speed regulation
-
7/29/2019 PS Basics of a DC Drive
22/37
Types of Regulation
Voltage
Current (Torque)
Speed Position
For discussion purpose, the regulation discussedwill be from 0 to base speed.
-
7/29/2019 PS Basics of a DC Drive
23/37
Types of Regulation
Voltage Regulator
Drive Regulates Armature Voltage
Feedback = Voltage & Current Speed Changes based on loading (5%)
IR Compensation
Improves regulation Measures current feedback
-
7/29/2019 PS Basics of a DC Drive
24/37
Types of Regulation
Current (Torque) Regulation
Adjusts armature voltage to change armature current
Feedback = Voltage & Current Drive will provide only the current (torque) it is told
-
7/29/2019 PS Basics of a DC Drive
25/37
Types of Regulation
Speed Regulation
Drive regulates speed of motor by changing armature
voltage Feedback = Speed &Current
-
7/29/2019 PS Basics of a DC Drive
26/37
Types of Regulation
Position Regulation
Drive regulates positioning device by changing the
armature voltage Feedback = Position & Current
-
7/29/2019 PS Basics of a DC Drive
27/37
Power Distribution Options
FlexPak 3000
Drive
M
Isolation Transform
Circuit Breaker
Line Reactor
Inverting Fault
Circuit BreakerContactor
-
7/29/2019 PS Basics of a DC Drive
28/37
Power Distribution Options
FlexPak 3000
Drive
M
Isolation Transform
Circuit Breaker Provides Impedance Reduce Electrical Noise
Isolation from ground
Protect from external
transients
Preferred for regenerative
applications
Provide power off switch
Overload capability
Thermal
Instantaneous
Current
-
7/29/2019 PS Basics of a DC Drive
29/37
Power Distribution Options
FlexPak 3000
Drive
M
Line Reactor
Inverting Fault
Circuit Breaker Contactor
Provides Impedance
Reduces Electrical
Noise
Mechanical disconnectto Motor
Provides power off switch
Overload
(Instantaneous Current)
-
7/29/2019 PS Basics of a DC Drive
30/37
Power Distribution Options
FlexPak 3000
Drive
M
Disconnect Switch
Provides power off
switch to drive
Less expensive
than circuit breaker
-
7/29/2019 PS Basics of a DC Drive
31/37
DC Drive Modifications
Blower Motor Starter
115 V Control Interface
Enhanced Field Supply
Electronic Field Trim (240 V Drives only)
Field Economy
Field Current Regulator
-
7/29/2019 PS Basics of a DC Drive
32/37
DC Drive Modifications
Blower Motor Starter
AC motor starter
Control of 3-phase blower motor
Fused with adjustable overload & interlocking
-
7/29/2019 PS Basics of a DC Drive
33/37
DC Drive Modifications
115 V Control Interface
Converts customer supplied 115 V to
24 VDC Inputs & Outputs
Run
Stop
Jog
Fwd/Rev
Auto/Man
Coast Stop
Customer Interlock
-
7/29/2019 PS Basics of a DC Drive
34/37
DC Drive Modifications
Enhanced Field Supply
Adjust field voltage to control field flux
Electronic Field Trim Changes Field Voltage/Current
Field Economy
Supply minimum voltage to keep motor warm
-
7/29/2019 PS Basics of a DC Drive
35/37
DC Drive Modifications
Field Current Regulator
Actually regulates field current
Improves regulation performance
-
7/29/2019 PS Basics of a DC Drive
36/37
DC Drive Terms
Constant Torque Variable Hp
Cogging
Full Wave / Half Wave Regulation (% of rated)
M Contactor
Contactor
Turn down Ratio
Enclosures (Page XIV)
-
7/29/2019 PS Basics of a DC Drive
37/37
Questions ???