DC Machine Types, Diagrams, and Control Systems
Classified in Technology
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DC Machine Types
Field or Parallel Shunt
- Field winding with many turns
- Small wire cross-section
- High resistance
- High inductance
- Field current is 1 to 4% of Inom
Field Series
- Low resistance
- Large cross-section
- Few turns
- Low inductance
Compound or Series and Parallel
- Part of the field is in series
- Low resistance
- Large cross-section
- Coils with few turns
- Low inductance
Independent Excitation
- Used for servo applications
- Auxiliary fields for weak-field switching
- Interpolate and is connected in series with armature
- Instability at high speeds
- Field-stabilizer used in shunting engines, connected in series with the armature
Control System
A control system is a device or group of devices used to control the operation of one or more electric machines.
Types of Diagrams
Connection (Wiring) Diagrams
- Devices are shown in their original positions (as installed).
- Shows all wires interconnecting devices.
- Wires are identified at their ends by numbers or letters, and may indicate insulation color.
Where are they used?
- During initial control system installation.
- For fault detection.
Block Diagrams
Characteristics:
- Each device is represented by a rectangle (double).
- Blocks are joined by lines with arrows indicating current direction.
Schematic Diagrams
- Control system devices are shown without physical arrangement.
- Shows connection cables (not identified at ends).
- Outlines arrangements with each component.
Use:
- For initial installation.
- For fault detection.
- To determine control system operation.
Line Diagrams
- Connections between control system devices are represented by a single line.
- Devices are placed in order of operation on each line.
- Usually separates control circuits from power circuits.