Power capacitors for induction furnace

Power capacitors for induction furnace

When you build medium frequency induction heating equipment or melting furnace, the capacitors optimal placement are necessary to consider. The capacitors play a role of power factor correction or improve loop characteristics.

The option is air-cooled capacitor or water-cooled capacitors in induction heating systems. Water-cooled capacitors are largely used in induction heating system because it capable of handling higher current than air-cooled capacitors.

Why choose water-cooled capacitors for induction furnace?

Compare with air-cooled capacitors, water-cooled capacitors offers: direct heat removal from dielectric losses; higher current density and continuous duty operation; reduced hot spots risk and dielectric aging.

From our past experience, a properly designed water-cooled capacitor banks can improve overall induction heating system efficiency by 2~5%, reduce temperature rise of IGBTs/thyristors; extend service life of coils, bus-bars, and other power electronics.

How to design power capacitors for induction furnaces?

Firstly, considering the optimal balance among current capability, thermal management, resonant stability, power device compatibility, and cost efficiency.Further consideration should focus on parallel configuration, cooling design, and system architecture.

For example, the operating range of 750~1000VAC for 5T,10T,15T medium frequency induction furnace, with continuous industrial melting demands.

Capacitor Configuration Recommendation ---5T,10T,15T induction furnace

●Option 1

750VAC water-cooled capacitor multiple parallel connection

Make the single capacitor unit 60~70% rated current

The best solution for 24 hours continuous melting demands

●Option 2

750VAC water cooled capacitor and modular capacitor units

Make 600~800microfarad capacitor as one capacitor modular

Independent cooling water tubes and independent monitor system

It will save maintenance cost and The failure of a single capacitor module does not affect the entire induction furnace.

●Option 3

1000VAC water cooled capacitor

Better applied for Frequency ≥ 800hz

Long bus-bar

Limited install space

●Other custom design options

Rated voltage ≥1500VAC

Dry type film capacitor for core-less induction furnace or other special working environment.

Successful Engineering Projects

A 15ton If induction melting furnace typically requires 3600μF~4200μF of 750VAC water cooled capacitors, with a loop current of 10~12KA. Parallel connection of multiple high-current water-cooled capacitors is the most proven and reliable solution for long-term continuous heating operating.

●15Tons intermediate frequency induction furnace

Power: 8MW

Frequency: 550~650Hz

Materials: Alloy Steel

Operation Condition: Continuous melting

Loop current: 10~12kA

working method: Series Resonance

●Capacitor Selection:

Water-cooled capacitor unit, 750VAC/150uf/ 1800A

Required quantity of capacitor: 26 nos

General capacity: 3900uf  

Deployment: Two rows of symmetrical parallel connections

Cooling method: independent cooling water tubes and independent flow rate monitor.

●Expected performance of induction furnace

Power factor: ≥0.98

Temperature rise of capacitors: <25K

Continuous operation: 24 hours

Designed life service: ≥8~10years