Starting device. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Automobile. Batteries, chargers

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Many motorists know the difficulties of starting the engine in winter. To facilitate this task, the industry produces special combined chargers with an additional starting function. Such charging and starting devices, as a rule, are connected in parallel with the battery when starting the engine.

The author of this article considers this method of starting a cold engine to be suboptimal and suggests using a powerful starting device that does not require a battery connection.

As practice shows, it is often necessary to start a car engine in winter using a charger-starter in two stages: first, recharge the battery for 10 ... In this case, the acceptable speed of the starter rotor was usually maintained for 20 ... 3 s from the moment of switching on, after which it decreased to values ​​that did not promise a start.

If the engine fails to start on the first try, the whole process has to be repeated from the beginning, and maybe more than once. All this is not only tiring, but also associated with overheating of the starter windings and wear, with a decrease in battery life.

A powerful starting device that can independently - without the help of a battery - spin the engine crankshaft at the required speed will help to avoid many troubles. What load power should the starting device provide?

In [1], it is indicated that the operating current Ir.b of the battery in the starter mode is Ir.b = 3Cb, where Cb is its nominal capacity in ampere-hours at normal temperature. The operating voltage Up of a twelve-volt battery in this mode is 10,5 V (1,75 V "per can"). Hence, the power Rst supplied to the starter of a car with a 6ST-60 battery with a capacity of 60 Ah,

Rst \u10,5d 3-60-1890 \u6d 55 W. An exception to the above is the 255ST-2677,5 battery, in which the operating starter current is XNUMX A and the power reaches Pst = XNUMX W.

The table summarizes information on the types and power of starters and batteries of the most common domestic cars [2].

Comparing the calculated power Рst of the starter with the nominal Рst nom, it is easy to see that Рst for cars is 2...2,5 times more than Рctnom, and even more for trucks. As experience has shown, the overall power of the mains transformer of the starting device, designed to work with cars, should not be less than 3,5 kW.

As a magnetic circuit for the network transformer of such a starting device, I used a set of stator plates from a burnt-out 5 kW asynchronous electric motor. The cross section of this toroidal magnetic core is SM = 27 cm2. Number of turns per volt

Therefore, the network winding must contain

nI \u1,11d 220 -244 \u16d XNUMX turns, and the secondary for an output voltage of XNUMX V

nII \u1,11d 2-16-36 \u3,6d 6 turns with a tap from the middle. An insulated wire with a cross section of 2 ... 25 mm40 is suitable for the primary winding, and 2 ... XNUMX mmXNUMX for the secondary.

The diagram of the starting device is shown in the figure. Switch SA1 must be rated for a current of at least 15 A and have a thermal protective device (for example, AE-1031).

If necessary, calculate the network step-down transformer with other parameters, you can use the methods described in [1,3].

A few tips for making a transformer. The magnetic circuit of the electric motor is freed from the remnants of the winding and from the steel or aluminum shell (housing). With a hammer and a sharpened chisel, the teeth of the magnetic circuit protruding inward are cut down. This operation is not difficult, you should only be careful - work with goggles and gloves.

The magnetic circuit is covered with a layer of epoxy resin and wrapped with two layers of fiberglass impregnated with resin. After the resin has hardened, winding begins. For the primary winding, a wire with increased insulation strength should be used - PEV-2, PETVL-2, PELR-2, LDPE, etc. If there is no single wire of the required cross section, it is permissible to wind it in two, three or even four wires.

After the primary winding is wound, it is connected to the network, the no-load current of the future transformer is measured. The current should not be more than 3,5 A. If it exceeds the specified limit, it is necessary to wind several turns in order for this condition to be met. The connection of the wires must be mechanically strong and necessarily soldered, preferably with refractory solder.

The primary winding is covered with two or three layers of fiberglass impregnated with epoxy resin, and after it has hardened, the secondary winding is started to be wound. When laying the coils, a wooden hammer is used to level and compact them, distributing them evenly along the length of the magnetic circuit.

For the secondary winding, any copper wire in strong heat-resistant insulation is suitable, as long as it can be wound on a magnetic circuit. In extreme cases, it is permissible to use a wire in rubber insulation, for example, PVKV. Outside, the winding should be wrapped with a fixing tape made of varnished fabric.

It is advisable to install the finished transformer on a stand made of boards (or by welding from steel angle bars). A thick duralumin or steel plate with diodes mounted on it and a negative output terminal in the form of an M12 threaded stud is attached to the stand. The positive clamp of the same design is mounted on a solid insulating plate. The SA1 switch is also attached to the stand.

The stand can be equipped with handles for carrying the transformer by two or alone. It is necessary to think over the entire design and manufacturing process of the device in advance so that in no case any of its elements form closed turns around the magnetic circuit.

The wires connecting the starting device to the car starter should be taken no less seriously. They should be as short as possible (in any case, not longer than 1,5 m), flexible, have reliable insulation and a copper cross section of at least 100 mm2. All connections must be made "under the nut". Any negligence here can be very expensive - from burns to the face and hands to a fire. Detachable connection with the starter should be made with special powerful clamps that exclude spontaneous separation. The wires must be clearly marked in polarity so as not to confuse them even in low light.

The operating mode of the starting device is short-term, its stay on under load usually does not exceed 10 s. After that, the device must be disconnected from the network and make sure that there is no overheating of the magnetic circuit, windings, connections, diodes and other elements. This is especially important at the beginning of the operation of the device.

If a three-phase network is used to power the starting device, its power can be significantly increased, which will make it possible to start the engines of powerful trucks, as well as tractors T-16, T-25, T-30, T-40, MTZ-80, etc. For the manufacture of such a starting device, ready-made transformers of industrial production TSPC-20A, TMOB-63, etc., connected to a network with a voltage of 380/220 V and having a secondary voltage of 36 ... 50 V, should be used.

Acquaintance with this technique must begin with a study of the relevant literature.

In conclusion, a few general considerations.

The use of a toroidal magnetic circuit for a transformer is completely optional. It is dictated only by its best weight and size indicators and the fact that it is often not difficult to purchase a "burnt out" electric motor. The power of such a toroidal transformer can be considered equal to the power of the electric motor, usually indicated on its case.

You should strive to calculate the wire cross section of the windings in such a way that the magnetic circuit window is fully used. As practice shows, the share of the primary winding accounts for about 55% of the filled area of ​​the window, and the share of the secondary - 45%.

When starting the engine, the battery may not be disconnected from the starter. In this case, the starting device can be connected to the battery terminals. To avoid overcharging, the device must be turned off immediately after starting the engine.

The described device consumes a lot of power from the network, its operation is associated with increased danger. Therefore, when using it, follow the safety rules, do not trust inexperienced and random persons to work with the device.

Literature

1. Shelestov IP Radio amateurs: useful schemes. - M.: Solon, 1998.
2. Ilyin N. M., Timofeev Yu. L., Vanyaev V. Ya. Electric equipment of cars. - M.: Transport, 1982.
3. Nikiforov I. Simplified calculation of a network transformer. - Radio, 2000, No. 10, p. 39.
4. Mikhalchuk A. N. Companion of a rural electrician. - M.: Rosagropromizdat, 1989.

Author: S. Gurov, village of Ilyinka, Rostov region.

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