What are the requirements for low-frequency heating equipment for 10 MVA transformer units?

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.