Baking Winding Varnish (OR 3xx)
Based on isophthalic alkyd resin; cured in an oven according to the recommended curing schedule. For series production and windings that demand maximum durability.
- High bond strength — holds the wires firmly
- Resistant to hot transformer oil
- High heat and moisture resistance, good flexibility
Technical information
| Series | OR 3xx |
|---|---|
| Resin | Isophthalic alkyd based |
| Curing | In an oven, following the recommended temperature–time schedule |
| Thinner | T-300 |
| General thinning ratio | 3 parts varnish : 1 part thinner |
| Application | Dipping (impregnation) |
| Key properties | High bond strength, resistance to hot transformer oil, high heat and moisture resistance |
Drying time, viscosity, solids content, packaging and shelf life are given in the product's technical data sheet (TDS). Request the TDS and safety data sheet (SDS) via WhatsApp.
When to use baking varnish
- You do series winding and want the same quality on every motor,
- The motor will run with vibration, at high speed or under heavy load,
- The winding will run in humid conditions, in a submersible pump or in hot oil,
- You have an oven and can plan the work.
Without an oven, use air-drying OR 1xx; baking varnish does not fully cure in air.
How to apply
- Clean the winding and dry it by preheating.
- Thin the varnish with T-300, generally 3 parts varnish to 1 part thinner.
- Impregnate by dipping; hold until bubbling stops.
- Let the excess drain.
- Place in the oven and follow the recommended temperature–time schedule. Start timing once the part reaches oven temperature.
- Do not remove early; let the motor cool completely before running it.
Points to watch
- Do not leave it to air-dry: The surface may look dry but the inside will not cure and stays tacky. See why winding varnish won't dry.
- Large parts take longer: Heavy stators and rotors reach oven temperature later; plan curing time accordingly.
- Keep the dip tank consistent: As solvent evaporates the varnish thickens; adjust with T-300.
- Do not mix with air-drying varnish: The two types are never combined in one tank.
Which varnish is right for you?
Tell us your motor type, operating temperature and application method, and we will send the suitable Orchem varnish and its TDS.
Frequently Asked Questions
Can I use baking varnish without an oven?
No. Baking varnish only cures fully when baked at the recommended temperature and time. If you have no oven, choose air-drying varnish.
What is the curing temperature and time?
The curing schedule depends on the product and is given in the TDS. Start timing once the part reaches oven temperature; this takes longer for large parts.
Can it be used in oil-filled transformers?
Yes. OR 3xx baking varnishes are resistant to hot transformer oil. Write to us for the right product for your transformer type.