Classification
Electrical machines are generally understood to include not only rotating and linear electro-mechanical machines but transformers as well. Transformers can be further classified according to such key parameters as follow:
- Power capacity: from a fraction of a volt-ampere (VA) to over a thousand MVA;
- Duty of a transformer: continuous, short-time, intermittent, periodic, varying;
- Frequency range: power-, audio-, or radio frequency;
- Voltage class: from a few volts to hundreds of kilovolts;
- Cooling type: (dry and liquid-immersed) self-cooled, forced air-cooled; (liquid-immersed) forced oil-cooled, water-cooled;
- Application: such as power supply, impedance matching, output voltage and current stabilizer or circuit isolation;
- Purpose: distribution, rectifier, arc furnace, amplifier output, etc.;
- Basic magnetic form: core form, shell form;
- Constant-potential transformer descriptor: power, step-up, step-down, isolation, high-voltage, low voltage;
- Three phase winding configuration: autotransformer, delta, wye, zigzag;
- Rectifier input phase-shift configuration: (n-winding -> p-pulse) 2-wdg -> 6-p, 3-wdg -> 12-p, . . . n-wdg -> *6-p; polygon; etc.)
- System characteristics: ungrounded, solidly grounded, high or low resistance grounded, reactance grounded;
- Efficiency, losses and regulation: excitation, impedance & total losses, resistance, reactance & impedance drop, regulation.
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