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What are the operating modes of transformers

yinhe — Fri, 05 Apr 2024 05:56:41 +0000

1. Parallel operation: Important power stations have two or more synchronous generator sets as the main power source. Two or more generators simultaneously supplying power to the grid is the process of parallel operation of generator sets, and the units are put into parallel operation. Also known as parallel operation, or parallel or full step operation.

2. Cold standby operation: refers to the situation where there are no safety measures on each side of the connected equipment, and there are obvious or identifiable disconnection points on each side of the connected equipment. The equipment itself has no abnormalities, and all circuit breakers and isolation switches are in the open position waiting for the closing command. Once closed, the equipment can operate normally.

3. No load operation: refers to the working state in which the primary winding of a transformer is connected to the power supply and the secondary winding is open circuit. At this point, the current in the primary winding is called the no-load current of the transformer. The no-load current generates a no-load magnetic field. Under the action of the main magnetic field, electromotive force is induced in the primary and secondary windings.

In summary, there are currently three operating modes for transformers: parallel operation, cold standby operation, and no-load operation.

How to maintain transformers

yinhe — Fri, 05 Apr 2024 05:54:50 +0000

The abnormal operation of transformers will lead to serious safety accidents. If regular maintenance and testing work is carried out according to the maintenance methods of transformers, it will ensure the safe and smooth operation of transformers.

Transformers should be maintained once before operation, and transformers in operation or shutdown should be regularly maintained once a year.

Maintenance methods for transformers:

1. Connect the backup transformer, disconnect the high and low voltage circuit breakers of the transformer to be repaired, remove the operation fuse of the power supply, close the grounding switch, fully discharge the transformer, lock the high voltage cabinet, and place a “stop closing” sign at the switch.

2. Maintenance of dry-type transformers, cleaning of ceramic sleeves and casings to ensure cleanliness and tidiness, inspecting the casings, gaskets, and ceramic sleeves for cracks, discharge marks, or aging of rubber pads, and checking for deformation of cables and busbars. Any problems should be promptly resolved.

3. Check if the contact surface of the busbar is clean. If there is an oxide layer on the contact surface, it should be removed and coated with electric composite grease.

4. Check whether the transformer is well grounded, whether the ground wire is corroded, and solve any problems in a timely manner.

5. Check each lead terminal, pin, grounding screw, and connecting bus screw. If there is any looseness, tighten it in a timely manner.

6. Clean the dust around the transformer and accessories, and check if the fire protection facilities and ventilation system are in good condition.

The working principle of transformers

yinhe — Fri, 05 Apr 2024 05:51:41 +0000

A transformer consists of an iron core (or magnetic core) and a coil, which has two or more windings. The winding connected to the power source is called the primary coil, and the remaining windings are called the secondary coils. It can transform AC voltage, current, and impedance. A simple iron core transformer is composed of an iron core made of soft magnetic material and two coils with different turns placed on the iron core. The function of the iron core is to strengthen the magnetic coupling between the two coils. In order to reduce eddy currents and hysteresis losses inside the iron, the iron core is made of coated silicon steel sheets stacked together; There is no electrical connection between the two coils, and the coils are wound with insulated copper wire (or aluminum wire).

One coil connected to an AC power source is called a primary coil (or primary coil), while the other coil connected to an electrical appliance is called a secondary coil (or secondary coil). The actual transformer is very complex, and inevitably there are copper losses (coil resistance heating), iron losses (iron core heating), and magnetic leakage (magnetic induction lines closed by air). The ideal conditions for a transformer to be established are: ignoring the leakage flux, ignoring the resistance of the primary and secondary coils, ignoring the loss of the iron core, and ignoring the no-load current (the current in the original coil when the secondary coil opens). For example, when a power transformer is operating at full load (with the rated output power of the secondary coil), it is close to the ideal transformer situation.

How to classify transformers

yinhe — Fri, 05 Apr 2024 05:50:43 +0000

1. Classified by purpose: there are power transformers, special transformers (electric furnace transformers, rectifier transformers, power frequency test transformers, voltage regulators, mining transformers, audio transformers, intermediate frequency transformers, high-frequency transformers, impulse transformers, instrument transformers, electronic transformers, reactors, transformers, etc.).

2. Classified by structure: there are double winding transformers, three winding transformers, multi winding transformers, and autotransformers.

3. Classified by cooling method: there are oil immersed transformers and dry-type transformers.

4. Classified by cooling methods: there are natural cooling, air cooling, water cooling, forced oil circulation air (water) cooling, and water internal cooling.

5. Classified by iron core or coil structure: core type transformer (plug-in iron core, C-type iron core, ferrite iron core), shell type transformer (plug-in iron core, C-type iron core, ferrite iron core), ring type transformer, metal foil transformer, radiation type transformer, etc.

6. Classified by the number of power phases: single-phase transformer, three-phase transformer, multiphase transformer.

7. Classified by conductive materials: there are copper wire transformers, aluminum wire transformers, and semi copper and semi aluminum, superconducting transformers, etc.

8. Classified by voltage regulation method: it can be divided into non excitation voltage regulating transformers and on load voltage regulating transformers.

9. Classified by neutral insulation level: there are fully insulated transformers and semi insulated (graded insulation) transformers.