An HBControls Power Controller is a solid-state relay pre-assembled onto either a DIN or panel-mount heat sink. Each Power Controller is ready-to-use, eliminating the need for thermal calculations or heat sink selection. The maximum allowable load current for the assembled solid-state relay in a 40°C ambient temperature is provided in the datasheet for each controller. Solid-state relays are electronic relays that, unlike electromechanical relays and contactors, have no moving parts. As a result, their lifespan is significantly longer than comparable electromechanical relays. The typical MTBF (mean time between failures) for a solid-state relay is >7 million hours. Solid-state relays can also operate significantly faster, with on/off times measured in cycles rather than seconds. An instantaneous (also called a "random turn-on) solid-state relay can switch power to a load is less than 100µS. Solid state relay power controllers are similar to electromechanical relays and mercury contactors in terms of functionality. All of these devices switch power to or from an electrical load upon the application of an input or control signal. As previously mentioned, solid-state relays contain no moving parts, making them faster, quiet and highly reliable. Some of the benefits of using a solid-state relay power controller are: * Longer life expectancy and number of operations * Resistant to shock and vibration * Silent operation - no acoustical noise * Fast response time * No mechanical or moving parts

In terms of function, all three switching technologies are very similar to each other. That is, each switches power to/from an electrical load when voltage is applied to their input. However, electromechanical relays and mercury contactors utilize mechanical contacts to perform the switching function. HBC Power Controllers utilize solid state relays, which have no moving parts and perform the switching function exceptionally fast without any acoustical noise. The lack of moving parts also means that the life expectancy of a Power Controller is significantly longer than a comparable mechanical relay.

The most common AC output Power Controllers utilize solid state relays with two back-to-back (inverse-parallel) SCRs in the output. These SCRs conduct load current when the AC sine wave is positive with respect to its anode. In other words, during a normal conduction cycle, one SCR will carry the full load current during ½ of the AC sine wave and the other will carry the load current once the polarity of the sine wave reverses. Most DC output Power Controllers utilize MOSFET solid state relays, which typically have a very low on-state impedance (Rds) and dissipate a minimal amount of power compared to AC output SSRs in applications below 100A of load current. Unlike AC output SSRs, DC controllers utilizing MOSFET SSRs can be wired in parallel to reduce power dissipation and effectively increase the maximum load-current rating. AC output controllers cannot be used to switch DC loads since the holding current of the SCRs will prevent them from turning off when the input signal is removed. The only exception is in applications where the load current is interrupted by other means. MOS