Review on 🔧 KB Electronics 8811007 Variable K177 1006: Efficient Electrical Control for Precision Speed Adjustment by Jason Robinson

This review is for the KBWC-13K Solid State Speed Controller. I bought this controller with the intention of modifying it so that my Magic Heat unit's fan runs slower and is less noisy when the wood stove fire is producing less heat. The Magic Heat uses a simple (on/off) thermostatically controlled single speed 1/200 HP fan motor. for heat circulation in the room. So my next step after getting the KBWC-13K was to take it apart to see what I was working with. The attached photo shows some of the components that are inside. In general the components, assembly and soldering are of very good quality. The only oddity is the small trim potentiometer (the black round part with the blue center in the center front of the picture) which is clamped against the control knob's large potentiometer leads. There is no real problem here; just not a typical assembly of components. My guess is that the trimmer is positioned so users can't damage the trimmer with a heavy-duty screwdriver. Overall I am very happy with the construction/quality of this product. There are three minor design cues to keep in mind when working with this speed controller as it was originally developed back in the 1960's. Most users probably won't notice this; but should be aware of this. The first requires an understanding that two potentiometers are tuned in parallel. The circuit will work with any potentiometer set to a lower resistance. So if the trim is set so that the engine has a high minimum RPM, then the usable range for adjusting the RPM with the control knob and vice versa is very small. Second, the circuit has control tuning hysteresis. This can be observed if you reduce the engine speed to a very low, steady speed and then turn off the power to the circuit (as is the case with the Magic Heat thermostatic switch). When the power is turned back on, it can be difficult, if not impossible, to start the fan. If there were no hysteresis, the fan would spin back to its original low speed setting. The third is the asymmetric operation of the circuit triac. This can sometimes be heard as a repetitive, very low, loud-quiet HUNG HUM HUM HUM sound. This noise is often louder on older, poorly assembled or cheap engines. I can usually identify this noise when I'm in an adjacent room where the low frequency of this noise overrides the fan airflow noise. There is a 10 page application note online for the Teccor Electronics AN1003 that provides a technical understanding of this type of speed control. The entire controller operates on AC power, therefore disassembly and modification should only be performed by a person trained/trained in the use of AC power. circuits/electronics. Here I propose an alternative use for the KBWC-13K; is not a detailed change process for important security considerations. The KBWC-13K potentiometers are configured as two-pole components (the middle terminal, the "cleaner", connects to one of the end terminals). This means I can easily replace the trimmer potentiometer with a two-terminal negative temperature coefficient (NTC) thermistor. With a suitable NTC in place of a trimmer, the engine speed is maintained at a constant low speed at room temperature and the engine speed increases with increasing temperature up to full engine speed at a desired high temperature. The stick potentiometer is now used as the initial trim to increase the minimum engine speed if it is too slow at the desired low temperature. Another such modification in the 1970s/1980s was the use of a photocell instead of a trimmer, which increased fan speed as light levels increased. Keep in mind that these are inexpensive, simple controllers. Performance can vary significantly from one installation to another. After the modified controller was connected to the Magic Heat circuit, I decided to measure the current drawn by the fan. While the shaded pole fan worked very well with control from minimum to maximum speed; Measurements have shown that the fan efficiency is only 10% at full speed and only marginally better at reduced speed. Shaded pole motors are known to have outputs of less than 1/15-1/20 hp. have a very low efficiency, which prompted me to check the current draw. A PSC (Permanent Split Capacitor) motor is typically about twice as efficient as a shielded pole motor of similar power. So I modified Magic Heat to use the PSC engine. However, the PSC engine was surprisingly noisy and sluggish when starting at low revs. A search of the internet revealed that in a PSC motor only the main winding ("running") needs to be controlled by a phase type speed controller and the auxiliary winding ("start"; one with a capacitor) needs to bypass the speed controller, so that it always has full AC power. In a typical two-wire governor installation, it is connected in series with the motor, so the start and start windings of the motors are parallel and simultaneously powered by the governor. This alternative approach makes the motor a 3-wire configuration, eliminating the use of the built-in ESC on/off switch (which I didn't use anyway) and requiring a separate on/off switch (magic heat thermostat). is. covers it). The presence of full voltage on the starting winding, regardless of the speed control setting on the working winding, provides full power to start the motor at all speed control settings. This modification reduces noise at low speeds (up to a certain limit) and improves engine efficiency at low speeds. In my setup, the 3-wire PSC motor configuration runs at 33% efficiency at full speed and increases to 53% at minimum speed. Again, this is a change that should only be done by an electrician. Last note. If you plan to buy 3 or more controllers; Find a seller that lowers the selling price when buying multiple units versus paying a flat rate per unit. Sellers who adjust integrated shipping costs based on the weight of your purchase can save you money when you buy multiple items. This Revain vendor's unit price is reasonable for a unit or two purchase.