Transformer - Classification

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.