Types and design of speed controllers for commutator motors. Self-production of an electric motor speed controller Connecting an electric motor speed controller

An acquaintance once asked me to look at and repair a homemade speed controller for an electric stove motor from his “penny.” He praised the regulator because it was possible to smoothly change the engine speed, but something broke in it.

The dimensions of the regulator body immediately alerted me, it was too bulky, when I took it apart I saw inside a massive radiator with a couple of KT819 transistors, still in a metal case, and some kind of circuit assembled by soldering leg to leg from which wires went to a variable resistor and to power transistors. The power transistors turned out to be broken. Since the engine consumed quite a bit of current, the power transistors, especially at low speeds, got quite hot. Considering such an adjustment scheme to be outdated, I decided to assemble a PWM (pulse width modulation) regulator with a powerful field-effect transistor as a key element. As the actual PWM modulator, it was decided to use the well-known 555 timer. It would seem that what can be done on a microcircuit that was developed more than 30 years ago. However, the range of applications for the 555 timer (our analogue of the KR1006VI1) is almost limitless. The use of basic operating modes and their modified variants allows the timer to be used in a variety of devices. It is known that the following basic functional devices can be assembled on chips of the 555 and 556 families:

• - monostable generator (one-shot);
• - generator - multivibrator;
• - time delay generator;
• - pulse width modulator;
• - pulse detector;
• - frequency divider.

The circuit of the electric motor speed controller turned out to be simple, with a minimum of external wiring:

I didn’t etch the printed circuit board for the electric motor speed controller, I just cut through the contact areas for the timer with a cutter:

I soldered the timer and assembled the kit.A powerful n-channel field-effect transistor with an insulated gate, the so-called Power MOSFET IRF540, is used as a key element.

I attached it to a small radiator - we select the dimensions based on the operating current of the electric motor. If it is small, then the transistor may not need cooling at all.

The regulator circuit, which is used to change the speed of rotation of the engine or fan, is designed to operate from an alternating current network at a voltage of 220 volts.

The motor, together with the power thyristor VS2, is connected to the diagonal of the diode bridge VD3, while the other receives an AC mains voltage of 220 volts. In addition, this thyristor carries out control with sufficiently wide pulses, due to which short circuit breaks, with which all commutator motors operate, do not affect the stable operation of the circuit.

The first thyristor is controlled by transistor VT1, connected according to a pulse generator circuit. As soon as the voltage on the capacitor becomes sufficient to open the first transistor, a positive pulse will be sent to the control terminal of the thyristor. The thyristor will open and now a long control pulse will appear on the second thyristor. And from it the voltage, which actually affects the speed, goes to the engine.

The rotational speed of the electric motor is adjusted by variable resistance R1. Since an inductive load is connected to the circuit of the second thyristor, spontaneous opening of the thyristor is possible, even in the absence of a control signal. Therefore, to block this, a diode VD2 is included in the circuit, which is connected in parallel to the L1 winding of the motor.

When setting up the engine speed controller circuit, it is advisable to use one, which can be used to measure the rotational speed of the electric motor, or a regular pointer voltmeter for alternating current, which is connected in parallel with the engine.

By selecting resistance R3, the voltage range is set from 90 to 220 volts. If the engine does not operate correctly at minimum speed, then it is necessary to reduce the value of resistor R2.

This circuit is well suited for adjusting fan speed depending on temperature.

It is used as a sensitive element. As a result of its heating, its resistance decreases, and therefore, at the output of the operational amplifier, on the contrary, the voltage increases and controls the fan speed through a field-effect transistor.

With variable resistance P1, you can set the lowest fan rotation speed at the lowest temperature, and with variable resistance P2, you can control the highest rotation speed at maximum temperature.

Under normal conditions, we set resistor P1 to the minimum engine speed. Then the sensor is heated and the desired fan speed is set with resistance P2.

The circuit controls the fan speed depending on the temperature readings, using a conventional negative temperature coefficient.

The circuit is so simple that it contains only three radio components: an adjustable voltage regulator LM317T and two resistances forming a voltage divider. One of the resistances is a negative TCR thermistor, and the other is a regular resistor. To simplify assembly, I provide a drawing of the printed circuit board below.

In order to save money, you can equip a standard angle grinder with a speed controller. Such a regulator for grinding housings of various electronic equipment is an indispensable tool in the arsenal of a radio amateur.

The U2008B microcircuit is a PWM speed controller for AC commutator motors. Manufactured by TELEFUNKEN, it can most often be seen in the control circuit of an electric drill, step saw, jigsaw, etc., and also works with motors from vacuum cleaners, allowing you to adjust the traction. The built-in soft start circuit significantly extends the life of the engines. Control circuits based on this chip can also be used to regulate power, for example, heaters.

All modern drills are produced with engine speed regulators built into them, but for sure, in the arsenal of every radio amateur there is an old Soviet drill, in which the change in speed was not intended, which sharply reduces the performance characteristics.

You can regulate the rotation speed of an asynchronous brushless motor by adjusting the frequency of the AC supply voltage. This scheme allows you to adjust the rotation speed in a fairly wide range - from 1000 to 4000 rpm.

The 220V electric motor speed controller allows you to change the frequency of either an electric motor designed to operate from a 220 volt network.

A fairly popular speed controller for 220 volt AC electric motors is a thyristor circuit. A typical circuit is to connect an electric motor or fan to the open circuit of the thyristor anode circuit.

One important condition when using such regulators is reliable contact throughout the entire circuit. The same cannot be said about commutator electric motors, since their brush mechanism creates short-term breaks in the electrical circuit. This significantly affects the quality of the regulator.

Description of the operation of the speed controller circuit

Below scheme thyristor speed controller, specifically designed to change the rotation speed of the collector electric motors(electric drill, milling cutter, fan). The first thing to note is that the motor, together with the power thyristor VS2, is connected to one of the diagonals of the diode bridge VD3, while the other is supplied with mains voltage 220 volt.

In addition, this thyristor is controlled by fairly wide pulses, thanks to which short-term shutdowns of the active load, which characterize the operation of the commutator motor, do not affect the stable operation of this circuit.

To control the thyristor VS1 on the transistor VT1, a pulse generator is assembled. This generator is powered by a trapezoidal voltage created as a result of limiting the positive half-waves by a zener diode VD1 having a frequency of 100 Hz. Capacitor C1 is discharged through resistances R1, R2, R3. Resistor R1 controls the discharge rate of this capacitor.

When the capacitor reaches a voltage sufficient to open transistor VT1, a positive pulse is sent to the control terminal VS1. The thyristor opens and now a long control pulse appears at the control pin VS2. And already from this thyristor, the voltage, which actually affects the speed, is supplied to the engine.

The rotational speed of the electric motor is controlled by resistor R1. Since an inductive load is connected to circuit VS2, spontaneous unlocking of the thyristor is possible, even in the absence of a control signal. Therefore, to prevent this undesirable effect, a diode VD2 is added to the circuit, which is connected in parallel to the excitation winding L1 of the electric motor.

Parts of the fan and electric motor speed controller

Zener diode - can be replaced with another one with a stabilization voltage in the region of 27 - 36V. Thyristors VS1 - any low-power with a direct voltage of more than 100 volts, VS2 - it is possible to supply KU201K, KU201L, KU202M. Diode VD2 - with a reverse voltage of at least 400 volts and a forward current of more than 0.3A. Capacitor C1 – KM-6.

Setting the speed controller

When setting up the regulator circuit, it is advisable to use a strobe, which allows either a pointer voltmeter for alternating current, which is connected in parallel with the engine.

By rotating the knob of resistor R1, the voltage range is determined. By selecting resistance R3, this range is set in the region from 90 to 220 volts. If the fan motor is unstable at minimum speed, then it is necessary to slightly reduce the resistance R2.

Smooth engine operation, without jerks or power surges, is the key to its durability. To control these indicators, an electric motor speed controller is used for 220V, 12V and 24V; all of these frequencies can be made with your own hands or you can buy a ready-made unit.

Why do you need a speed controller?

An engine speed controller, a frequency converter, is a device with a powerful transistor, which is necessary to invert the voltage, as well as to ensure smooth stopping and starting of an asynchronous motor using PWM. PWM – wide-pulse control of electrical devices. It is used to create a specific sinusoid of alternating and direct current.

The simplest example of a converter is a conventional voltage stabilizer. But the device under discussion has a much wider range of operation and power.

Frequency converters are used in any device that is powered by electrical energy. Governors provide extremely precise electrical motor control so that engine speed can be adjusted up or down, maintaining revs at the desired level, and protecting instruments from sudden revving. In this case, the electric motor uses only the energy needed to operate, instead of running it at full power.

Why do you need a speed controller for an asynchronous electric motor:

1. To save energy. By controlling the speed of the motor, the smoothness of its start and stop, strength and speed, you can achieve significant savings in personal funds. As an example, reducing speed by 20% can result in energy savings of 50%.
2. The frequency converter can be used to control process temperature, pressure or without the use of a separate controller;
3. No additional controller required for soft start;
4. Maintenance costs are significantly reduced.

The device is often used for a welding machine (mainly for semi-automatic machines), an electric stove, a number of household appliances (vacuum cleaner, sewing machine, radio, washing machine), home heater, various ship models, etc.

Operating principle of the speed controller

The speed controller is a device consisting of the following three main subsystems:

1. AC motor;
2. Main drive controller;
3. Drive and additional parts.

When the AC motor is started at full power, current is transferred with the full power of the load, this is repeated 7-8 times. This current bends the motor windings and generates heat that will be generated for a long time. This can significantly reduce engine longevity. In other words, the converter is a kind of step inverter that provides double energy conversion.

Depending on the incoming voltage, the frequency regulator of the speed of a three-phase or single-phase electric motor rectifies the current of 220 or 380 volts. This action is carried out using a rectifying diode, which is located at the energy input. Next, the current is filtered using capacitors. Next, PWM is generated, the electrical circuit is responsible for this. Now the windings of the induction motor are ready to transmit the pulse signal and integrate them into the desired sine wave. Even with a microelectric motor, these signals are issued, literally, in batches.

How to choose a regulator

There are several characteristics by which you need to choose a speed controller for a car, machine electric motor, or household needs:

1. Control type. For commutator motors, there are regulators with a vector or scalar control system. The former are more often used, but the latter are considered more reliable;
2. Power. This is one of the most important factors for choosing an electrical frequency converter. It is necessary to select a frequency generator with a power that corresponds to the maximum permissible on the protected device. But for a low-voltage motor it is better to choose a regulator more powerful than the permissible watt value;
3. Voltage. Naturally, everything here is individual, but if possible, you need to buy a speed controller for an electric motor, the circuit diagram of which has a wide range of permissible voltages;
4. Frequency range. Frequency conversion is the main task of this device, so try to choose a model that will best suit your needs. Let's say, for a manual router, 1000 Hertz will be enough;
5. According to other characteristics. This is the warranty period, the number of inputs, the size (there is a special attachment for desktop machines and hand tools).

At the same time, you also need to understand that there is a so-called universal rotation regulator. This is a frequency converter for brushless motors.

There are two parts in this circuit - one is logical, where the microcontroller is located on the chip, and the second is power. Basically, such an electrical circuit is used for a powerful electric motor.

Video: electric motor speed controller with SHIRO V2

How to make a homemade engine speed controller

You can make a simple triac motor speed controller, its diagram is presented below, and the price consists only of parts sold in any electrical store.

To work, we need a powerful triac of the BT138-600 type, it is recommended by a radio engineering magazine.

In the described circuit, the speed will be adjusted using potentiometer P1. Parameter P1 determines the phase of the incoming pulse signal, which in turn opens the triac. This scheme can be used both in field farming and at home. You can use this regulator for sewing machines, fans, tabletop drilling machines.

The principle of operation is simple: at the moment when the motor slows down a little, its inductance drops, and this increases the voltage in R2-P1 and C3, which in turn leads to a longer opening of the triac.

A thyristor feedback regulator works a little differently. It allows energy to flow back into the energy system, which is very economical and beneficial. This electronic device involves the inclusion of a powerful thyristor in the electrical circuit. His diagram looks like this:

Here, to supply direct current and rectify, a control signal generator, an amplifier, a thyristor, and a speed stabilization circuit are required.

Not every modern drill or grinder is equipped with a factory speed regulator, and most often speed control is not provided at all. However, both angle grinders and drills are built on the basis of commutator motors, which allows each of their owners, even if they know how to handle a soldering iron, to make their own speed controller from available electronic components, either domestic or imported.

In this article we will look at the diagram and principle of operation of the simplest engine speed controller for a power tool, and the only condition is that the engine must be a commutator type - with characteristic lamellas on the rotor and brushes (which sometimes spark).

The above diagram contains a minimum of parts and is suitable for power tools up to 1.8 kW and above, for a drill or grinder. A similar circuit is used to regulate speed in automatic washing machines that have commutator high-speed motors, as well as in dimmers for incandescent lamps. Such circuits, in principle, will allow you to regulate the heating temperature of a soldering iron tip, an electric heater based on heating elements, etc.

The following electronic components will be required:

Constant resistor R1 - 6.8 kOhm, 5 W.

Variable resistor R2 - 2.2 kOhm, 2 W.

Constant resistor R3 - 51 Ohm, 0.125 W.

Film capacitor C1 - 2 µF 400 V.

Film capacitor C2 - 0.047 uF 400 volts.

Diodes VD1 and VD2 - for voltage up to 400 V, for current up to 1 A.

Thyristor VT1 - for the required current, for a reverse voltage of at least 400 volts.

The circuit is based on a thyristor. A thyristor is a semiconductor element with three terminals: anode, cathode, and control electrode. After a short pulse of positive polarity is applied to the control electrode of the thyristor, the thyristor turns into a diode and begins to conduct current until this current in its circuit is interrupted or changes direction.

After the current stops or when its direction changes, the thyristor will close and stop conducting current until the next short pulse is applied to the control electrode. Well, since the voltage in the household network is alternating sinusoidal, then each period of the network sinusoid the thyristor (as part of this circuit) will work strictly starting from the set moment (in the set phase), and the less the thyristor is open during each period, the lower the speed will be power tool, and the longer the thyristor is open, the higher the speed will be.

As you can see, the principle is simple. But when applied to a power tool with a commutator motor, the circuit works more cleverly, and we will talk about this later.

So, the network here includes in parallel: a measuring control circuit and a power circuit. The measuring circuit consists of constant and variable resistors R1 and R2, capacitor C1, and diode VD1. What is this chain for? This is a voltage divider. The voltage from the divider, and what is important, the back-EMF from the motor rotor, add up in antiphase, and form a pulse to open the thyristor. When the load is constant, then the open time of the thyristor is constant, therefore the speed is stabilized and constant.

As soon as the load on the tool, and therefore on the engine, increases, the value of the back-EMF decreases, since the speed decreases, which means the signal to the control electrode of the thyristor increases, and opening occurs with less delay, that is, the power supplied to the engine increases, increasing the dropped speed . This way the speed remains constant even under load.

As a result of the combined action of signals from the back-EMF and from the resistive divider, the load does not greatly affect the speed, but without a regulator this influence would be significant. Thus, using this circuit, stable speed control is achievable in each positive half-cycle of the network sinusoid. At medium and low rotation speeds this effect is more pronounced.

However, with increasing speed, that is, with increasing voltage removed from the variable resistor R2, the stability of maintaining a constant speed decreases.

In this case, it is better to provide a shunt button SA1 parallel to the thyristor. The function of diodes VD1 and VD2 is to ensure half-wave operation of the regulator, since the voltages from the divider and the rotor are compared only in the absence of current through the motor.

Capacitor C1 expands the control zone at low speeds, and capacitor C2 reduces sensitivity to interference from brush sparking. The thyristor needs to be highly sensitive so that a current of less than 100 μA can open it.