PC Series Proportional Output
Solid State Power Controllers
Frequently asked questions
What is a proportional solid state relay power controller?
Proportional output solid-state relays and power controllers are used to provide only a percentage of power to an AC load, ranging from 0-100%. The amount of power applied to the load is determined by the analog input signal. They are ideal for applications where precise control over the amount of power switched to an AC load is required. Proportional solid state relays and power controllers are primarily used in resistive heating applications, although phase-angle solid state relays are commonly used in light-dimming applications.
What’s the difference between burst fire and phase-angle control modes?
A PC series solid state relay or power controller can provide proportional power to an AC load in two different manners; phase-angle or burst fire switching, depending upon which mode is selected on the relay. If the solid state relay is set to phase-angle mode, then the output will only conduct at certain points of the AC sine wave. The point at which it begins to conduct is dependent upon the analog input provided. For example, if the selector switch on the solid state relay is set to Mode B (phase-angle mode, 0-10V analog input), then the percentage of power applied to the load will be directly proportional to the 0-10V analog input. If the signal is at 5V, then the output will turn on at the peak of each AC sine wave, effectively applying 50% power. If you’re controlling a heating element and the temperature starts to go beyond the set-point with 50% power being applied, then your controller may reduce its output to 4V. If so, then the solid state relay would reduce the power to 40% by only conducting load current once 60% of the AC sine wave had passed.
Burst fire mode performs the same function. However, unlike phase-angle mode, the solid state relay will provide a series a full AC cycles to the load when set to burst fire mode. We can use the same example as above, except with the selector switch on the solid state relay set to Mode E (burst fire mode, 0-10V analog input). Instead of turning on at the peak of each AC sine wave when the analog input is at 5V, the solid state relay will provide a series of full AC cycles to the load and then turn off for the same number of cycles. If the analog input is reduced to 4V, then the solid state relay will still provide a series of full AC cycles, but the on-off ratio of the relay output will drop to 40%.
What control modes are available on the PC series solid state relay power controllers?
The PC series solid state relays have 6 possible combinations of output control mode and analog input mode. The mode desired is selected via a selector switch on the face of the solid state relay.
Mode A – phase-angle switching, 0-5V analog input
Mode B – phase-angle switching, 0-10V analog input
Mode C – phase-angle switching, 4-20mA analog input
Mode D – burst fire switching, 0-5V analog input
Mode E – burst fire switching, 0-10V analog input
Mode F – burst fire switching, 4-20mA analog input
Is an auxiliary power supply required for the PC series solid state relays?
If the solid state relay is set to 0-5V or 0-10V analog input mode (modes A, B, D and E), then an external supply capable of providing between 8Vdc and 30Vdc is required to power the internal microprocessor. If the solid state relay is set to 4-20mA analog input mode (modes C and F), then an auxiliary power supply is not required.
How does the internal over temperature protection feature work on the PC series solid state relays?
When utilized within specifications (rated load current, ambient temperature, etc..), the over temperature function will likely never trigger. However, in cases where load current or ambient temperature becomes excessive, the solid state relay will turn itself off if the internal temperature begins to reach levels that could damage internal components. The solid state relay will begin to function normally once the internal temperature drops below minimum safe levels.
What is meant by “contactor configuration”?
While there are a variety of different solid state relay and power controller configurations, two of the most common are “relay configuration” and “contactor configuration”. Both terms are simply based on the historical designs of solid state relays and electromechanical contactors. “Relay configuration” implies that the output terminals are located on one side of the solid state relay, while the input terminals are located on the opposite side of the solid state relay. This is how most industry standard “hockey puck” solid state relays are configured.
“Contactor configuration” has become increasingly popular over the past two decades as newer, more narrow-in-width solid state relays are introduced into the market. With these relays, the output terminals are located on opposite ends of the solid state relay. This allows for the narrower designs since load current conducts through the semiconductors and lead frames throughout the length of the solid state relay, as opposed to restricting the entire ‘system’ to one side of the solid state relay. The input connector for contactor configured solid state relays is usually located on the middle of the relay, although some products may locate them at different locations.