In electrical heating purposes, resistive heaters are powered by way of section angle-controlled SCR/triac circuits to fluctuate the utilized voltage/energy to keep up the required temperature.
Part angle management produces quite a lot of harmonics resulting in energy line disturbances.
Wow the engineering world along with your distinctive design: Design Concepts Submission Information
Determine 1’s circuit offers a easy and cost-effective resolution with out introducing harmonics. This controller skips a sure variety of energy cycles in between, to fluctuate energy to the warmers.
Determine 1 Circuit schematic of mains cycle skipping controller, this controller skips a sure variety of energy cycles in between, to fluctuate energy to the warmers.
On this typical design, 10 full cycles are taken as base. Timer U3 (555) by way of R2, R4, and C1 decides this by giving output pulses with an interval of 200 ms, which is the width of 10 full AC cycles of a 50 Hz AC mains (for a 60 Hz mains, this will likely be 166.6 ms). These pulses set off U4 (555) monostable to supply pulses with an adjustable width inside 200 ms, by adjusting potentiometer RV1. This pulse practice controls an optotriac with zero cross detector U2 (MOC3033) to set off triac U1 (BTA25-600BW). The triac conducts at some point of “off pulse widths” produced by U4. Thus, these conduction durations enable the chosen variety of voltage cycles to cross by way of and impress on load. Throughout “on pulse widths”, the triac doesn’t conduct and skips the voltage cycles. Simulated waveforms may be seen in Determine 2 with two full cycles being skipped and Determine 3 with 5 full cycles being skipped.
Determine 2 Simulated waveforms with the U3 timer output (yellow), U4 timer output (blue), and heater voltage (pink). Eight full cycles are impressed on load, skipping two full cycles as determined by the RV1 potentiometer place.
Determine 3 Simulated waveforms with the U3 timer output (yellow), U4 timer output (blue), and heater voltage (pink). 5 full cycles are impressed on load, skipping 5 full cycles as determined by one other RV1 potentiometer place.
For example, if a 40 ms width is chosen by RV1, which corresponds to 2 full cycles of a 50 Hz mains, the triac is not going to conduct for two voltage cycles and can conduct for 8 full cycles and cross to the load. Thus, two cycles are skipped. This operation repeats. Thus, load energy is managed by skipping a specific variety of voltage cycles. As AC cycles handed to load are full cycles, undesirable harmonics are eradicated.
Usually such controllers are realized with an MCU and software program, the novelty of this circuit realizing the identical operate with out utilizing the MCU, thus making it easy with low value elements.
Jayapal Ramalingam has over three a long time of expertise in designing electronics techniques for energy & course of industries and is presently a contract automation marketing consultant.
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