The device and repair of household hair dryers

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This electrical appliance - a hair dryer - is very popular and often indispensable in everyday life. Due to high consumer demand, the designs of most hair dryers have become very similar, and the workmanship and price have dropped. Today it is very difficult to buy a truly durable hair dryer. The practice of repairing hair dryers of various brands suggests that the breakdowns that occur are of the same type and, as a rule, are not fatal, but are easily removable without serious financial expenses.

Any electric hair dryer in its design contains two main, large elements: a fan and a heater. The fan drives air through the heater (heating element), sucking it in behind the hair dryer and ejecting it from the front when heated.

Hair dryer device for drying hair.
1 - propeller; 2 - electric motor; 3 - heater; 4 - thermal protection; 5 - mode switch; 6 - power cable.

For household hair dryers, the fan is built on the basis of low-voltage (12-18 V) collector DC motors. Such a motor cannot be powered directly from the 220 V AC mains. To achieve the required voltage drop, a separate coil (let's call it a step-down coil) is used inside the heating element. To rectify the voltage, a full-wave rectifier (diode bridge) is used, mounted by a hinged mounting on the contacts of an electric motor. A plastic propeller, consisting of three or more blades, is mounted on the metal shaft of the engine.

The heating element of the hair dryer is a frame made of fireproof material with several windings of nichrome wire (spiral). Depending on the number of operating modes of the hair dryer, there can be two or three windings, one of which is lowering.

Heating element with two windings.

Hot coils of the heating element must be constantly blown with cold air, especially when operating at maximum power. If, for any reason, the air supply has become insufficient or has completely stopped (for example, the engine has failed), then, for reasons of fire safety and in order to avoid burnout of the heating element, the hair dryer should automatically turn off. Such an emergency shutdown occurs due to the presence of two temperature-sensitive elements in the hair dryer device at once - two "protection lines" inside the heater.

The first "frontier" is the thermostat. It is a pair of closed contacts attached to. Being close to the outlet of heated air, the contacts are intensively blown by it. When the outgoing air reaches a critical temperature, the contacts move away from each other, the power supply circuit of the hair dryer is opened. After a few minutes, when the bimetallic plate cools down, the contacts close again and the hair dryer turns on.

Bimetallic thermostats.

If the above protection did not work for any reason at the right time, then a few seconds later the "second line" of protection - a thermal fuse - is activated. This fuse is disposable and needs to be replaced after blown.

Fusible thermal fuse.

Hair dryer Rowenta CV 4030.

To see the internal structure of a household hair dryer, let's take a look at its typical representative - Rowenta CV 4030. This model is equipped with a fan based on a low-voltage motor, the heating element consists of one downward spiral and two heating ones. The hair dryer has three operating modes, in the first mode the fan speed is lower than in the other two. A schematic diagram of this hair dryer is presented below.

In the first position of the switch SW1 mains supply passed through the plug XP1, filter C1R1, protective elements F1, F2, diode VD5(necessary to cut off one half-wave of the alternating voltage) goes to the downward spiral H1, through it the electric motor is powered M1... Diodes VD1-VD4 necessary for straightening a lowered spiral H1 alternating voltage. Inductors L1, L2 and capacitors C2, C3 serve to reduce interference arising from the operation of the brush motor. Through diode VD5 power is also supplied to the heating coil H2.

When flipping the switch SW2 to position "2", diode VD5 short-circuits and goes out of the game. The engine starts to run at maximum speed, the spiral H2 heats up more. Third position of the switch slider SW2 corresponds to the mode of maximum power consumption when parallel to the spiral H2 spiral connects H3... In this position, the outlet air temperature is at its highest. The "cool" button is included in the break of both heating coils, when it is pressed, only the electric motor remains on through the coil H1, helix H2 and H3 are de-energized.

The process of opening the hair dryer Rowenta cv4030.

Hair dryer in semi-disassembled form.