Analog thyristor power supply challenges:

• At control outputs below 100%, analog SCRs (silicon controlled rectifiers) cause high harmonic distortion on the power supply and a poor power factor, as well as a significant decline in energy efficiency

• Due to poor power factor, energy is wasted in the system, leading to unnecessary extra costs for filters and capacitor banks

• Analog thyristors cause difficulties in the control of the furnace heaters. Temperature stability and accuracy cannot be achieved causing process repeatability issues

Download the heat treatment vacuum furnace SCR power supply replacement success story

Variable reactance transformer challenges:

• Deadband regions make the control loop more difficult to set up and adjust, resulting in unstable heater control
• Harmonics are inherent in VRT systems, therefore a water cooling system is needed to compensate for the heat losses
• Clogged water pipes need regular maintenance that can damage the dielectric insulation resulting in safety issues

The challenges of analog thyristor power supplies also apply.

Download the heat treatment vacuum furnace VRT power supply replacement success story

Lower energy costs

Typical energy savings ≈10% with a return on investment in ≈ 2 years or less. ^[1]

• Typical power factor better than 0.9 helps to meet the limits set by utility suppliers, reducing the risk of penalty charges
• Predictive load management can stabilize power demand, helping to reduce peak demand charge penalties

^[1] Return on investment is dependent upon local energy rates

Improve furnace performance

High accuracy temperature measurement and precision power control help to improve workpiece throughput and quality:

• Repeatable performance throughout the furnace temperature range
• Achieve higher Nadcap furnace class temperature uniformity

Reduced unplanned downtime

Improved power efficiency combined with diagnostics help to improve overall system robustness.

• Less equipment to maintain
• Monitoring of key parameters provides diagnostics for faster maintenance
• Advanced notification of heater deterioration enables pre-ordering and scheduling of replacement parts
• Predictive load management can keep the power demand within the capability of the power line, helping to reduce the risk of power outages

CapEx savings

Investment is often lower than an analog controller (SCR) or VRT solution

• No need for additional power factor correction systems
• Transformers and power controllers can be air cooled, or water cooled using the furnace cooling system
• The footprint of a digital solution is generally smaller
• Ethernet connectivity reduces the cost of cabling
• Greenfield power distribution systems can be smaller due to load sharing and shedding, which balances and controls the energy demand on the general site supply