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吉田 陽一

吉田 陽一

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  • For a 10 MVA power transformer the low‑frequency heating (LFH) unit must be sized to deliver the heating current and control needed to raise winding temperatures to the drying range while avoiding core saturation and overstressing insulation. Practically this means an LFH with adjustable low frequency (typically 0.5–10 Hz), smooth output voltage control (0–400 V range), and sufficient AC output current to produce the required I²R heating in the windings. You also need accurate temperature and moisture monitoring (target winding/oil temperature ~+75°C to +120°C and moisture reduction to <10 g/ton), automatic control/interlocks and appropriate site ratings (ambient operation 0–40°C, weather/IP protection, no condensation). Safety grounding, overcurrent protection and operator interlocks are mandatory.

    Standard low‑frequency heater modules offer up to ~300 A output (sinusoidal output noted to about 200–300 A depending on spec) and can be customized or paralleled, but a 10 MVA transformer’s rated winding current depends on system voltage (for example ~525 A on an 11 kV side, ~289 A on a 20 kV side), so off‑the‑shelf 300 A units may be undersized for some 10 MVA cases. To size correctly, provide the transformer’s rated voltage(s) and measured winding DC resistance so the required heating current (P = I²R for desired heating power) can be calculated; options are a higher‑current/custom LFH, paralleled units or heating via a different winding/tap arrangement. If you want, give the transformer voltage and winding R and I’ll estimate the required LFH current and suggest a suitable configuration or customization.

    Thanks — that link is correct. For petrol, diesel and oil blended with additives the preferred solution is hydrodynamic cavitation flow‑blending (GlobeCore’s USB family) because it delivers intensive, repeatable homogenization in a flow, handles multi‑component formulations (typically 2–7 feeds), and can often replace separate stabilization/blending tanks. These units are available from lab/pilot scale (USBL‑1/USB‑1) up to industrial throughputs (models around 18–100 m3/h and higher), can be skid or container mounted, built for hazardous areas, and configured with heating/cooling, circulation and smooth interfaces to filtration, settling or adsorbent stages so you can control mixing intensity and residence time for coagulation or adsorption steps.

    When choosing a specific mixing vessel or USB configuration, size it to your required throughput and number of ingredients, confirm whether the process is continuous or batch, check viscosities and temperature control needs, specify required residence time (20–30 minutes is common for adsorption/coagulation), and declare hazardous‑area classification plus any footprint constraints. If you give your target flow (m3/h or batch size), number/type of additives, desired residence time and whether you need inline filtration or adsorbents, I’ll recommend a specific USB model and skid configuration.

    For transformer insulation drying, GlobeCore offers hot air drying systems such as Mojave Heat units. These systems generate controlled hot air flow that passes through transformer windings, removing moisture effectively. Compared to traditional drying methods, they provide faster and more uniform drying without excessive thermal stress. This makes them suitable for maintenance and refurbishment of power transformers.

    For turbine lubricants with viscosity from 10 to 2000 mm²/s and flow ?60 L/min, a reliable solution is vacuum dehydration and filtration using GlobeCore equipment. Units like the CMM series combine heating, vacuum degassing and fine filtration, allowing removal of free and dissolved water, gases and particles while stabilizing oil properties. This approach is far more effective than simple filtration for long-term oil conditioning in power plants.

    Ferromagnetic steels concentrate magnetic flux, reducing magnetizing current and enabling efficient voltage transformation. Modern cores use grain-oriented silicon steel or amorphous metal for minimal hysteresis and eddy losses.

    in reply to: How to calculate power factor in transformer? #332195

    Power factor is calculated as PF = kW / kVA. For transformers, PF reflects load characteristics rather than the transformer itself. Under no-load, PF is low due to magnetizing current and core losses; under load, PF depends on downstream inductive or capacitive equipment. Utilities use PF in loss calculations, billing, and reactive power compensation.

    in reply to: how does a power pole transformer work? #332171

    A power pole transformer is a small distribution transformer mounted on utility poles that steps medium voltage down to low voltage for homes and businesses. Medium voltage from overhead lines feeds its primary winding. The transformer’s core and windings convert this to lower voltage on the secondary, typically arranged in single phase or split phase for residential service. The tank is oil filled for insulation and cooling, and bushings connect primary and secondary conductors. Protective devices such as fuses and lightning arresters are installed nearby to protect against faults and surges.

    in reply to: What does a power pole transformer fuse protect against? #331791

    The fuse protects the transformer from overcurrent and fault conditions on the secondary or internal failures. It interrupts current before thermal damage, limiting fault energy and preventing pole equipment destruction.

    Technical specifications include kVA/MVA rating, primary and secondary voltages, vector group, frequency, cooling class (ONAN/ONAF/ODAF), impedance, losses, insulation level/BIL, tap-changer type, temperature rise, bushings, protection accessories, and applicable standards (IEC/IEEE). Specs define how the transformer integrates into a grid or industrial system and set procurement and testing requirements.

    It measures conductor integrity, joint quality, and OLTC contact condition. Variations indicate loose joints, carbonized contacts, or winding damage.

    It is described as a core component that transfers bulk power, controls voltage, isolates sections and supports stability through impedance and tap control.

    DC converter transformers benefit from proper tap settings to optimize voltage regulation and reduce conduction losses. Thermographic inspections reveal hotspots in windings, bushings, and OLTC contacts, allowing proactive corrective maintenance and extending insulation life.

    Common three-phase groups include Y-Y, ?-?, Y-?, ?-Y, and zig-zag variants, chosen for grounding, phase shift, and harmonics.

    in reply to: Who manufactures CG power transformers? #330416

    CG-branded power transformers originated from Crompton Greaves/CG Power, a company known for manufacturing distribution, medium power, and large power transformers for utilities and industry. Over time, ownership and branding structures have evolved, but CG-type transformers generally refer to products from a manufacturer specializing in MV/HV equipment, with factories and service centers focused on IEC/IEEE-compliant designs for international markets.

    Autotransformers share windings between primary and secondary with no full isolation; power transformers have separate windings for galvanic isolation and improved insulation.

    A Hammond wiring diagram shows primary and secondary winding configurations, tap leads, grounding points, and recommended connection schemes for different input and output voltages. It indicates terminal markings, phase relationships, and sometimes vector groups, enabling installers to configure series or parallel connections correctly. The diagram also highlights shielding, dual or multiple primaries/secondaries, and any connection precautions. This ensures safe installation, correct voltage outputs, and proper phasing in industrial panels or equipment.

    in reply to: Where is a 150 MVA power transformer used? #330234

    150 MVA class transformers are used in transmission and sub-transmission substations, large industrial complexes, HVDC converter terminals, and large renewable export substations. At this capacity level they support significant load blocks and provide grid interconnection between 110-400+ kV classes depending on regional standards.

    GlobeCore provides oil testing equipment including kinematic viscosity meters for transformer and turbine oils. The requested specifications match the automatic KV-5000 class. A quotation with warranty, calibration standards, and service details will be provided.

    The UVR and CMM-R series regeneration systems remove acids, sludge, and other degradation products from transformer oil, restoring its chemical and dielectric properties. The regenerated oil can be reused in various industrial applications.

    GlobeCore stationary vacuum drying units remove moisture from transformer cores and windings through controlled heating and deep vacuum. Installation requires standard electrical and oil-circulation connections. Operation includes heating, vacuum stage, and monitoring cycle. The unit can be customized for 60 Hz supply, but 120 V is insufficient for heating; a 3-phase 400-480 V source is required.

Viewing 20 posts - 1 through 20 (of 72 total)

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