Frequently asked questions
What is a Proportional Output Power Controller?
A proportional power controller is similar to a “standard on/off” power controller in that it switches power to/from an AC load. However, proportional controllers provide a percentage of AC power to the load in direct proportion to the analog input signal applied. This can either be a 0-5, 0-10, 4-20mA, or similar form of analog input. The output of the power controller will provide a percentage of AC power to the load equivalent to the percentage of the analog input signal applied. For example, if 5Vdc is applied to the input of a proportional power controller with a 0-10V input setting, then the output will provide 50% power to the load.
Proportional output power controllers are ideal for dimming applications or in heating systems where tight temperature control is required.
What is the difference between Phase-Angle and Burst Fire (time proportion) control?
Phase-angle controllers turn-on at different points of the AC sine wave, effectively applying a percentage of the AC power to the load. The point at which they turn on is in direct proportion to the analog input provided. If, for example, a 3V signal is applied to a controller with an analog input range set to 0-10, then the output of the controller will not turn on until 70% of the AC sine wave has passed. Since a 3V signal is 30% of the full 0-10V analog input range, the power controller will only switch 30% of the AC sine wave to the load.
Burst-fire controllers also apply proportional power but do so by providing a series of full AC cycles to the load. If we use the same example as above, applying a 3V input to a burst fire power controller with a 0-10V analog input will also result in 30% power being applied to the AC load. However, depending upon the controller, this would be accomplished by conducting load current for 3 full AC cycles and then turning off for the next 7 AC cycles.
Both are effective methods for proportionally controlling a load, but there are a few points to consider when deciding which mode is best for your application. When conducted emissions are a concern, burst fire controllers are typically used since they generate less electrical noise than phase-angle controllers. However, burst fire controllers are not recommended for lighting loads because the off duration may be significant enough to create a noticable flicker effect.
For reference, the
LPC series power controllers provide phase-angle control of loads, while the
TP series and
TPLP series power controllers provide burst fire control of loads. The
PC series power controllers have a selector switch on the solid state relay that can be set to either phase-angle or burst fire control.
What’s the difference between Burst Fire and Burst Fire Loop power controllers?
Both burst fire and burst-fire loop power controllers apply proportional power by providing a series of full AC cycles to the load. However, burst-fire loop (TPLP series burst fire power controllers) are only available with a 4-20mA analog input. The advantage with burst-fire loop power controllers is that an external 24Vac supply is not required. Therefore, if you’re using 4-20mA control and need a burst fire power controller, the burst-fire loop controllers are the best choice for your application.
Can proportional output power controllers be used to control a three-phase load?
Yes, although the wiring is slightly less straightforward than with a standard on/off AC multiphase power controller. Three LPC series phase-angle power controllers (or one three-phase LPC series power controller) can be used to control all three phases of a Wye with neutral or Delta configured three-phase load. For loads in Wye configuration with a neutral connection, each of the three LPC series power controllers are in series with one phase of the AC mains. For loads in Delta configuration, the LPC controllers must be inside the Delta in order for the controllers to function properly.
Two TP series burst fire power controllers can be used to control three-phase loads in Delta configuration or Wye without a neutral. Both two and three-phase TP series proportional controllers are available, but the preferred method is to control only two phases since it reduces overall power dissipation by 33%. This allows for slightly higher load-current ratings and also reduces overall costs.
In both cases, the input terminals of the solid-state relays are wired together to ensure simultaneous switching of all three phases. User manuals are available at
https://www.hbcontrols.com/technical-docs. You can also contact our technical support team at 800.879.7918 / firstname.lastname@example.org if you’d like to discuss in more detail the options for proportionally controlling three-phase loads.