The Many Benefits of SCR Power Control

Industrial manufacturers and plant engineers need a reliable, flexible and cost effective way to control power to electric heaters used in their plant's manufacturing processes. Of all the controls available, silicon controlled rectifiers (SCRs) best meet those needs. The precise control offered by SCRs extends heater life, reduces maintenance costs and improves product quality even at today's faster production speeds.

What is an SCR?

Silicon controlled rectifiers are special four-layer semiconductor devices that are primarily used in high-power applications. They are used to control such devices as relay controls, electric motors and induction heating elements. Depending on how they are biased, they can be operated in one of three modes: forward blocking mode off state, forward conducting mode on state or reverse blocking mode off state.

What is an "SCR Power Controller?"

An "SCR power controller" is a solid state, microprocessor-based switching device that provides proportional control of electric power on an infinitely variable time basis. Because SCRs are solid state, they can rapidly cycle on and off more than a billion times. This feature allows maximum control over heating processes and extends the heater life.

What Are the Benefits of SCR Power Controllers?

Longer Heater Life

Most heating elements are constructed of wire, which becomes brittle with extensive use, especially if the wire is exposed to extreme temperatures due to thermal overshoot and undershoot. When heating elements are exposed to long cycle times, they expand and contract more, leading to thermal shock. However, the shorter cycle times of SCR power controllers reduce that effect, which leads to much more precise temperature control.

Longer Controller Lifespan

Additionally, mechanical relays tend to spark, arc and burn out much faster than SCR power controllers. Although mercury displacement relays do a better job than mechanical relays, their cycle time is also relatively long, ranging in time from three to 15 seconds. They can also overheat and explode if cycled too fast. Again, this is not a problem with SCRs. Other benefits of SCR power controllers include the following:

• Operate in both digital and analog environments

• Multiple types of feedback: voltage, current and power.

• Able to retransmit load voltage, load current and load power.

• Reduced maintenance costs
• Improved response time
• Silent operation
• Closer process control
• Reduced peak power consumption
• No arcing and sparking

• Allows setting of limits, setpoints and alarms

• 6 different digital communication protocols

What Options Are Available in SCR Power Controllers?

As can be seen on the website of Control Concepts, SCR controllers are available in a number of configurations, including single-phase and three-phase. Both AC and DC outputs are available in voltages that range from 24 to 690 volts with current ratings of eight to 2000 amps. Four firing modes are available as shown below:

1. Phase Angle
2. Zero Cross
3. Zero Cross Transformer Mode
4. Burst

Control Concepts

Control Concepts is a leader in the design, manufacture and application of SCR power controllers. They deal only in high-reliability products that are able to survive in the most punishing environments. They can also provide specialty products, such as optically coupled SCR gate drives that virtually eliminate false operations caused by transients. If you need help in finding a reliable solution for your application, give us a call today at 952-474-6200.