What types of solid-state relays are used in HBControls power controllers?

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AC output power controllers utilize SCR-based, AC output solid-state relays, while most DC output power controllers utilize Crydom MOSFET output solid-state relays. The load-current rating of the solid-state relay used in the assembly is dependent upon the overall load-current rating of the power controller itself. For example, a power controller rated for 50 amps @ 40°C will most likely use a 90 amp solid-state relay, and a power controller rated for more than 80 amps will likely use 125 amp solid-state relays. This is because the actual load-current rating of a solid-state relay is determined by the thermal impedance of the heat sink to which it is mounted.

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Will I need to mount the solid-state relay to the heat sink, or do they come pre-assembled as shown on the website?

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The solid-state relay is already assembled onto the heat sink. This is the primary advantage of an HBControls power controller, since it eliminates the need for thermal calculations, sourcing of multiple components and in-house assembly. They’re essentially “plug & play” as-is, capable of switching the specified load-current rating at a 40°C ambient temperature. Stand-alone solid-state relays are also available from HBControls, but some form of heat sink is typically required in order to dissipate the heat generated by the solid-state relay during normal operation.

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Why do power controllers need a heat sink for the solid-state relay?

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AC output solid state relays are not perfect switches, having a forward voltage drop (Vf) of approximately 1Vrms when in the on state. Therefore, they dissipate power in the form of heat at a rate of about 1W per ampere of load current. An SSR switching 50 amps of load current will dissipate approximately 50W of power. For the sake of simplicity, if we assume that the thermal conductivity of air is 20°C/W, then the base plate of a solid-state relay would reach roughly 1,000°C when carrying 50 amps while suspended in free air. It would, of course, actually melt long before then, but the calculation makes the point.

HBControls Power Controllers utilize highly efficient heat sinks to prevent the solid-state relay from overheating during normal use. Datasheets for each controller provide maximum allowable current ratings in a 40°C ambient temperature, eliminating the need for thermal calculations, heat sink selection and assembly.

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What are the benefits of using power controllers / solid-state relays instead of electromechanical relays, contactors or mercury displacement relays?

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1. Life expectancy – the typical MTBF (mean time between failures) for an HBControls power controller is >7 million hours. Essentially, when utilized within their specifications, a solid-state power controller will far outlive the life of the equipment in which it’s installed.
2. Silent operation – “clicking & clacking” is a common annoyance with electromechanical relays and contactors, especially in commercial and residential applications. Solid-state power controllers do not generate acoustical noise when switching power to/from the load.
3. Shock & vibration resistance – The lack of moving parts in a solid-state relays eliminates concern over mechanical contact bounce as a result of systemic shock and vibration.
4. Fast operation – zero-crossing solid-state relays and power controllers can switch power to a load in less-than one AC cycle (8.33ms or 10ms), while instantaneous turn-on (or “random”) solid-state power controllers can switch power to a load in less than 100 microseconds of receiving an input signal.
5. PLC compatibility – unlike electromechanical relays and contactors, the input of a solid-state power controllers only requires a few milliamps of current in order to switch power to an AC load. Most power controllers will “trigger” with less than 10mA of input current, although some power controllers utilize solid state relays that will switch power to the load with less-than 5mA of input current.
6. Environmentally friendly – unlike solid-state relays and power controllers, mercury displacement relay and contactors, by definition, contain mercury. Also, the brief life expectancy of electromechanical relays and contactors (often less-than 300k operations, which can translate to months or weeks in some applications) means that hundreds, if not thousands of mechanical relays are ultimately replaced and disposed-of before a single end-of-life power controller or solid-state relay failure.

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1. What is a “Proportional Control” power controller?

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Unlike standard “on/off” power controllers, a proportional power controller can provide a portion of AC power to the load. The amount of power provided ranges from 0% to 100%, dependent upon the input signal applied. Most HBControls power controllers have a selectable analog input, such as 0-10V, 0-5V, 4-20mA or potentiometer control. They are ideal for dimming applications or in heating systems where tight temperature control is required. Two types of proportional power controllers are available; phase-angle controllers and burst fire controllers.

Phase-angle controllers apply a portion of the AC power to the load by turning on at various point of the AC sine wave. While this effectively controls the amount of power going through the load at a given time, it can also generate a significant amount of conducted emissions since they often turn on closer to the peak of the AC sine wave. Therefore, additional filtering is required when installed in applications requiring some level of compliance with EMC standards.

Burst-fire controllers also apply proportional power but do so by providing a series of full AC cycles to the load. In other words, if the input is set to 0-10V and a 5V signal is applied, the controller may conduct for 10 full AC cycles and then turn off for the next 10 AC cycles. Burst fire controllers are commonly used as an alternative to phase-angle controllers in applications where conducted emissions are a concern. However, they are typically not suitable for lighting applications since the on-off period can potentially create a noticeable flicker.

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1. Can HBControls customize a product for a specific application?

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Yes. While there are always limitations, customized power control solutions are a significant part of our business. Please contact our support team at 800.879.7918 / support@hbcontrols.com if you’d like to discuss your specific application requirements.

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1. Where can I find additional information on solid state relays and power controllers from HBControls?

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Additional information on HBControls power controllers and solid-state relays is available on our website at https://www.hbcontrols.com/faq. You can also contact our support team at any time - 800.879.7918 / support@hbcontrols.com. We look forward to hearing from you.

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What are "stripwire" power controllers?

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Stripwire power controllers perform the same function as AC output single and multiphase power controllers. The only difference is the type of solid state relay used in the assembly. Most power controllers utilize solid state relays with "saddle clamp" terminals, which are ideal for termination with ring or fork terminals. Stripwire power controllers utilize solid state relays with box-clamp terminals, which are suitable for bare wire termination.

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