沧灿潘5GN30RAA东方马达
Pearson pulse transformers feature a minimum of solid insulation in regions of high electric field. This type of construction prevents damage to the transformer by accidental flashovers due either to poor oil or to overvoltages beyond the typical 50 to 100% safety factor built into the transformer. The intentional weakest region is between the high voltage corona ring and the core. These are metal surfaces and flashovers between them have negligible effect on the surfaces for the energies involved in even the highest power line-type pulsers.

In spite of the voltage stand-off safety factor built into the transformer, and the feature of being able to withstand reasonable flashovers without damage, there are still occasional cases of damaged transformers. On inspection these units invariably show that they have been operated in oil that was dirty or there have been enormous over-voltages, sometimes approaching a million volts for a unit rated at a small fraction of this value. It is hoped that the following notes will help the user avoid these difficulties.

The necessity for good oil is generally accepted, but often the specific precautions necessary are not understood. Pulse modulator malfunction is not so generally appreciated as an important? and frequent cause of accidental overvoltages. In fact, it is often a major source of trouble. Over-voltages can be difficult to detect and the causes difficult to diagnose.

INSULATING OIL

Ordinary transformer insulating oil supplied by the major oil and electrical companies is basically satisfactory for high voltage pulse use. The problems that arise are most frequently due to
contamination by dirt, air and water. The condition of the oil as initially installed must be good. Once installed satisfactorily, one must assure that it stays good.

Dirt During Installation?

Reasonable effort should be made to be sure the transformer itself, the tank, and the other parts in the oil are free from dust, lint, chips, etc. before filling. It is difficult to get all the parts absolutely clean. The slightest amount of dirt in the oil can be a potential source of flashover when it drifts through a region of high electric field.

Filtering the oil is normally indicated at this point.

Filtering After Installation

The oil filter element should be of a type that filters very small particles. "Fuller's Earth" filters, or equivalent, capable of filtering fine particles are necessary. If a filter unit is? part of the transformer tank assembly, running the filter unit for a period of a few hours before operation will clean up most of the dirt particles. If there is no continuous filtering unit, placing the inlet and outlet hoses of the pump and filter in diagonally opposite corners of the tank will give most rapid filtering of the oil volume.

Keeping Dirt Out of the Oil

Once the oil is clean, several precautions should be taken:
Put a lid on the tank and keep it there. Remove only for short periods of time for initial inspection if necessary. Once operation of the unit is going smoothly, the cover and gasket should be bolted in place.
Do not put hands in oil without filtering the oil afterwards. Even clean hands and arms seem to deteriorate the oil.
If an accidental over-voltage results in a flashover, the oil will have a small amount of carbon in it, weakening the oil. Filtering is a wise thing to do if any spark-overs occur.
If the oil should inadvertently become so carbonized that it becomes perceptibly darkened, then the oil is weakened to the point where corona tracks can be established on the solid insulation on which the transformer windings are wound. Once corona tracks are established, which can happen at less than rated voltage once oil is badly weakened, the tracks will grow until complete breakdown occurs.

Occasional Sparkover in First Few Hours of Operation Sometimes it is found that, although performance of the modulator is perfect and the oil very clean, a sparkover may occur after several hours of running time. This can be explained by the presence of a lone piece of dirt, perhaps a nearly invisible piece of lint, which is drifting slowly about in the transformer tank. It can take hours of drifting before it enters a region of high electric field. The sparkover demolishes the particle, and the resultant flashover contaminants may become so disbursed as to cause
no further trouble.

Continuous Filtering

In a stably operating system, with no over-voltages, thoroughly clean oil, sealed tank, and no undetected corona from some sharp high voltages points in the tank, there should be no need for continuous filtering. But if all these conditions are not certain to prevail at all times, the expense of downtime and its attendant mess can be largely avoided by continuous filtering.

Oil Testing

A standard 60 Hz oil tester can be used to check pulse transformer oil. The breakdown point of the oil should be at least 30 kV rms for a standard oil cup with electrode spacing of 0.1 inch.

The oil test cup (and also any other vessel used for dipping up the oil) should be rinsed in clean oil, other than the oil to be tested, so as to avoid possible contamination of the oil to be tested. Oil should be taken from the transformer tank as used in operation. Repeated tests should be made. The lowest reading is the significant one since the density of contaminants can be low.