Power supply b5 21 characteristics. Typical malfunctions and methods of their elimination

The technical description and operating instructions are intended to familiarize with the basic technical data, composition, device, operation of the DC power supply "B5-21", as well as with the procedure for operation and maintenance.

The direct current source "B5-21" is a device assembled on semiconductor devices and provides a stabilized voltage at the output terminals, adjustable from 0 to 30 V at a load current of 0 to 5A and from 0 to 10V at a load current of 0 up to 10 A. The source is a portable laboratory device and is intended to power filament circuits and circuits on semiconductor devices.

The operating conditions of the source are:

• ambient temperature from 283 to 308 K (from + 10 to + 35 ° C);
• atmospheric pressure 86 -g106 kPa (650 h-800 mm Hg);
• relative air humidity up to 80% at a temperature of 298 K (+ 25 ° C);
• supply voltage 220 ± 22 V at a frequency of 50 ± 0.5 Hz and harmonic content up to 5%.

Design

Structurally, the source is designed as a portable device.

All the main controls and controls are installed on the front panel:

1. power on indicator;
2. toggle switch for turning on the network;
3. voltmeter;
4. ammeter;
5. OVERLOAD indicator;
6. switch for coarse setting of the output voltage;
7. potentiometer for smooth adjustment of the output voltage;
8. output terminals;
9. housing terminal.

On the back wall there are:

• fuse;
• output voltage calibration potentiometer;
• overload current setting potentiometers;
• source ground terminal.

Rice. 1. External view of the direct current source "B5-21".

Technical details

The range of regulation of the output voltage is from 3 to 30 V in steps of 2 volts with smooth regulation within the step. The error in setting the output voltage is no more than 100 mV.

The source allows load currents from 0 to 10 A with an output voltage of up to 10 V and from 0 to 5 A above 10 V. The nominal value of load currents is 10 and 5 A, respectively.

The error of indicator devices reduced to the end of the scale is not more than 2%.

Instability of the output voltage at the output terminals when the supply voltage changes by ± 10% of the nominal value should not exceed 0.05% at Uout> 5 V and 0.1% at 3 V< Uвых < 5В.

The instability of the output voltage when the load current changes from nominal to zero should not exceed 0.5% at an output voltage of 3 to 10 V and 0.1% at an output voltage over 10 V.

The drift of the output voltage for 8 hours of continuous operation does not exceed 0.2% at an output voltage of 5 to 30 V and 0.5% at an output voltage of 3 to 5 V.

The voltage change when the ambient temperature changes by 1 ° C (temperature coefficient of voltage) does not exceed 0.1% in the range of the ambient temperature from 283 to 308 K (from +10 to + 35 ° C) at an output voltage of 3 to 30 V ...

The effective value of the ripple voltage does not exceed 0.05% of the output voltage, with an output voltage of 3 to 5 V and 0.02% over 5 V.

The regulating bodies of the protection circuit must ensure its operation at load currents of 8-12A at an output voltage of up to 10V and З-7A at an output voltage of over 10 V.

The output impedance of the source in the frequency range from 20 Hz to 200 kHz does not exceed 0.5 Ohm.

The permissible modulation factor must be at least 0.05 and 0.1 of the rated load currents of 10 and 5 A, respectively.

The maximum overshoot must be no more than 0.6 V, the settling time must be no more than 500 ms, the number of overshoots must be no more than two.

The characteristics of the source are verified when the device is operating under normal conditions:

• ambient temperature 293 ± 5 K (+ 20 ± 5 ° C);
• relative humidity 65 ± 15%;
• atmospheric pressure 100 ± 4 kPa (750 ± 30 mm Hg);
• supply voltage 220 ± 4.4 V, 50 Hz.

The source is powered from an alternating current with a voltage of 220 ± 22 V, a frequency of 50 ± 0.5 Hz.

The source allows continuous operation for 8 hours, keeping the parameters within the specifications.

Warm-up time is 5 minutes, the time for establishing a mode under rated load to obtain guaranteed instability from changes in input voltage at rated load is 1 hour.

The average uptime of the source is 3000 hours.

The power consumed by the source does not exceed 480 VA.

The mass of the device is no more than 28 kg.

Source dimensions do not exceed 488x270x433 mm.

The device and operation of a constant current source

Description of the wiring diagram

The source operates according to the usual sequential regulation scheme. The electrical structural diagram is shown in Fig. 2.

Rice. 2. Electrical structural diagram.

The power supply or the actual rectified voltage source consists of a power transformer T1, a rectifier bridge VD1 - VD4 on silicon diodes of type D242A and an L-shaped filter consisting of a choke L1 of type DT-6A and a capacity of 4000 μF, which is formed by 8 capacitors C8, C9.

The primary winding of the power transformer has taps used for coarse adjustment of the output voltage.

The regulating element consists of two stages connected in series - a buffer and a regulating one, each of which is a composite transistor.

The buffer stage is designed to reduce the power dissipated on the pass-through transistors VT8, VT7 (P210A) of the control stage, and is the first composite transistor. It consists of two parallel-connected transistors VT4, VT5 (P210A), shunted by a resistor R17, and transistors VT3 (P213B) and VT2 (MP26A). Between the base and the emitter of the first composite transistor, a counter-bias voltage taken from the resistor R13 is connected, and the source of E.D. C, presented in the form of a voltage drop across the transistors VT8, VT7 (P210A).

At the maximum mains voltage and maximum load current, the emitter-collector voltage of transistors VT8, VT7 (P210A) increases and transistors VT4, VT5 (P210A) from saturation mode go into amplification mode; there is a redistribution of power between transistors VT4, VT5, VT8, VT7 (P210A) and resistor R17.

The regulating stage is designed to stabilize the output voltage of the rectifier. It is a second composite transistor assembled from two transistors VT8, VT7 (P210A) connected in parallel and transistors VT7 (P216) and VT6 (P214A).

An error signal of the comparison circuit is fed to the base of this composite transistor from the DC amplifier, which changes the internal resistance of the through-flow transistors VT8, VT7 (P210A), which ensures the stabilization of the output voltage.

The DC amplifier is assembled on a VT11 transistor (1T403I), the load of which is a resistor R21.

Rice. 3. Schematic diagram of the direct current source "B5-21".

Attention! When using the switch for the coarse setting of the output voltage, it is necessary to pay attention to the clarity of fixing the positions to prevent the failure of the power transformer.

If the “OVERLOAD” signal turns on, turn off the source, remove the load, turn on the source again, smoothly increase the load to the rated one.

Note. Potentiometers "UST. OVERLOAD CURRENT "when the device is released, they are set to trigger the protection circuit at a load current of 5.5 - 7 A, with an output voltage over 10V and 10.5-12 A with an output voltage of up to 10 V.

Setting the operation of the protection circuit for a load current within 3 - 7 A is done using potentiometer R6, and for a load current within 3 - 12 A - using potentiometers R6 and R7.

Typical malfunctions and methods of their elimination

When repairing the source, it is necessary to comply with all safety rules when working with voltages up to 1000V.

To access the inside of the source, it is necessary to unscrew 4 screws on the side walls and remove the upper and lower casing of the device.

Tab. 1. A list of the most common or possible malfunctions.

If transistors, zener diodes or diodes fail, they are replaced with the same type. In this case, it is necessary to clarify the upper limit of the output voltage. The upper limit of the output voltage is set by potentiometer R42, located on the back of the device.

When replacing transistors VT8, VT9 (P210A), it is necessary to establish the equality of the emitter currents using the potentiometer R24.

Choke DT-6A

Toroidal magnetic core MT-160, inner diameter 60, outer diameter 92 mm. Steel grade E330, tape 0.35x60 mm. Assembly method: 2 mm gap ± 10%.

The no-load current of the inductor at a voltage of 15 V on the primary winding is not more than 2.3A.

Rice. 4. Choke DT-6A.

Tab. 2. Choke winding data.

Tab. 3. The mode of its own rectifier (at a mains voltage of 220 V - 2% and a load current of 5A).

Power transformer

Toroidal magnetic core MT-300, inner diameter 74 mm, outer diameter 118 mm.

Steel grade E330, tape 0.35x60 mm. Power of the transformer is 400 VA.

No-load current of the primary winding at taps 6-3 at a voltage of 220 V not more than 280 mA.

Tab. 4. Winding data of the power transformer.

Ferroresonant transformer

Toroidal magnetic core MT-30, inner diameter 42 mm, outer diameter 70 mm.

Steel grade E330, tape 0.35x30 mm.

Assembly method: 0.3 mm gap ± 10%.

No-load current of the primary winding at taps 5-6 at a voltage of 220 V no more than 100 mA.

Tab. 5. Winding data of a ferroresonant transformer.

Tab. 8. List of elements to the schematic diagram of the B5-21 device.

Rice. 5. Template for restoring the scale of the voltmeter of the direct current source "B5-21".

Rice. 6. Template for restoring the scale of the ammeter of the direct current source "B5-21".

During the repair of equipment, as well as in the design and various experiments in radio electronics, there is often a need to use a laboratory power source. A power supply that provided the required supply voltages for the various circuits. There is no universal power supply that would provide a wide range of voltages and currents at once. Therefore, depending on the tasks, several power sources for low, high voltages and currents are used.

Someone assembles a power source on their own, under the voltages and currents he needs. And someone buys ready-made factory laboratory power supplies. How to choose a power supply for laboratory purposes?

We will consider a number of power supplies, their features and selection criteria. If you are an active radio amateur and do a lot of testing, then you need a very reliable power source.

First, you need to determine for yourself that a laboratory power supply should be simple schematically, inexpensive, reliable and had a large power reserve and a margin for careless handling - this important point includes protection in case of short circuit, protection failure and, at the same time, with the power supply everything normally, the overcurrent is many times higher than the declared one, maintainable, have good stabilization parameters, convenient and reliable voltage regulation methods, as well as simple and convenient monitoring of voltage and current.

Homemade power supplies- they are usually designed for narrowly targeted purposes, when, for example, a certain voltage and current are needed. In this case, its assembly is justified. I have designed power supplies based on transformers of different power, according to the usual stabilization schemes, their main drawback is the voltage drop at high current. And also the lack of convenient controls and a suitable body. Voltage sag could be eliminated by adding a voltage reference, but this required additional assembly costs. Therefore, if you need one kind of voltage and a certain current, then you can make a power source yourself.

Switching power supply -

Extremely robust design. But it is more necessary for certain voltages and currents. It cannot be called universal. Very good voltage stabilization, it works out the declared power, if it is correctly calculated. And also more than the declared power can work up to a certain limit. Usually they are used when small dimensions and high current are needed. I have tested 12V switching power supplies for LED modules, 100W and 400W. These power supplies hold current very well and shed voltages to a minimum. The main disadvantage is the interference they throw into the 220V network. and interfering with the work of the equipment, especially the reception. Surge protectors help to fight interference, but the spectrum of interference is quite wide and it is not possible to extinguish everything. There are regulated power supplies, but they are rather crude and give off a lot of noise. There are expensive sources, but this is a different category that we are not considering.

Linear laboratory power supplies- Most suitable for universal purposes. These are power supplies made on power transformers. They are inexpensive, affordable and reliable. However, they do not emit interference into the network.

For repairing car amplifiers and subwoofers, amplifiers, testing various radio electronics, powering micromotors, lamps, etc. need a power supply from 0 to 30V. with current up to 10-20A.

What power supplies can you consider? My recommendation is to use Soviet military acceptance devices - B5-21.

DC power supply B5-21 manufactured by the Velikie Luki Instrument Plant.

Characteristics of the power supply B5-21:

Output voltage range - 0V-30V;

Relative instability of the output voltage - less than 10-2 when the mains voltage changes by ± 10%; less than 10-1 when the load changes by 100% for a current equal to 10A, and 5 ∙ 10-2% for a current equal to 5A;

Relative temperature coefficient of voltage B5-21 - ± 0.1% / ºС;

Relative ripple voltage - no more than 0.03%;

Power consumption B5-21 - 480V ∙ A;

Overall dimensions - 490x270x410mm;

Weight B5-21 - 28kg.

This is how the B5-21 springs were collected by women at the Velikie Luki Instrument Plant.

The direct current source B5-21 is of a linear type, has a toroidal-type power transformer, a power reserve of approximately 400W. The choke is also made on an impressive toroidal core. It has a reference voltage source made on a separate toroidal transformer with ferroresonant stabilization of the mains voltage.

Features a solid metal body, die-cast chassis, thick stamped base metal, aluminum reinforced top cover, and thick aluminum sheet front bezel. The source is practically indestructible, it works under load for a long time, you can power any electronics, the current can give more if you adjust the protection operation threshold. The protection is performed on the REN-48 relay, it is simple, even if it does not work, nothing critical will happen. The source is working.

What's inside B5-21?

Transformers

There are three of them. Power - the largest, support and choke.

All transformers are toroidal, which cannot be said about the power source, for example, the Bulgarian-made TPP 5010. There is one W-shaped transformer. Torus have higher efficiency and higher power with small overall dimensions. Power transformer - about 400W. The primary winding is connected to a rotary switch, thus regulating the voltage at the output of the source. For many power supplies, the voltage is controlled by a switch on the secondary side of the power transformer. In B5-21 it is done differently. This solution is more optimal, because there is a higher current on the secondary winding and when switching under load, sparks are possible on the switch contacts. The current here according to the passport is 10 Amperes, so this decision is correct. But the power source B5-7 has a current of up to 3 Amperes and the secondary winding switches.

Rectifier diodes - D242A - Stand on radiators, thick aluminum plates.

Powerful pass-through transistors - 4pcs P210A - are installed on large radiators, at the bottom of the radiator there is a fan operating from a 220V network. Thus, the radiator is blown through by the air flow.

Capacitors - 8 pcs, 2000 uf each. It is not worth changing, they turned out to be alive.

Above, there is a hinged mounting, below in the "basement" there is one board with a reference voltage stabilizer.

There is a fine adjustment of the voltage within 3 volts. Basic voltage regulation with a biscuit switch.

The power wiring is soundly made, where significant current flows, a thick wire was used, the rest of the wiring is neatly laid in a bundle and tied with threads.

Surprised in this power source is the choke - it is on a toroidal split core, quite impressive in size. Now such chokes are very rarely found in modern technology. The power transformer itself is also on a toroidal core, of impressive dimensions. All transformers are wrapped in fabric, impregnated.

What modifications and what repairs can be done when using B5-21?

I got this power supply in its entirety, working, I bought it for 1500 rubles. However, when turned on, it hummed strongly. It turned out that the fan for blowing the radiators of the transistors operates from a 220V network. And it is quite noisy, it has only four blades at right angles, which are inherently noisy by design. In addition, when I disassembled the fan motor, I discovered that the bearings were worn out - they were backlash. I did not order a new fan motor. it would still make a significant noise, since worked at high revs, and I needed a silent power supply. Therefore, instead of the standard fan, I installed a 120 mm fan from the computer, fixing it with screws from the bottom. Computer fan power supply - 12V. I decided to feed it from my own source. Therefore, I purchased an additional transformer and assembled a simple rectifier and smoothing capacitor circuit. The transformer is connected in parallel to the main transformer B5-21 to the 220V network. The fan speed was regulated by a resistor connected in series. Now the noise from the fan is the same as from the computer.

However, the buzz did not disappear at all. It turned out that the reference voltage transformer was humming, it is the smallest in size there. Why he was buzzing, I had to find out. Having removed it, I measured the idle current. He turned out to be normal. So there were no wire closures inside. After reading the passport and instructions for B5-21, I found out that it was made on a split core. It is possible that over time, the impregnating varnish in the cut dried out and an air gap formed, which led to the hum of the transformer. I impregnated the transformer with yacht varnish, but the buzz still remained, although it diminished. Then I decided to exclude from the circuit the capacitor, which is connected in series to the primary winding of the transformer. Such a switching circuit is provided for stabilization against surges in the 220V mains voltage. It is essentially a ferroresonant stabilizer. It stabilizes the mains voltage from surges, but its disadvantage is that when the mains voltage frequency changes to 50Hz, it no longer works as it should.

Why is the core of the reference voltage transformer split? Because this is done to saturate the core more. A voltage of about 400V is generated on the primary winding connected through a 0.5μF capacitor, so the transformer hums like this, and over time it hums louder from vibration, because the impregnation dries up. I disconnected the capacitor from the primary winding and powered it directly from the 220V network. The humming stopped immediately. There is a small sound that is no longer so annoying. This had no effect on the operation of the power supply as a whole. It worked stably, which was fine for me. You can order such a transformer new, or give the old transformer for vacuum impregnation, and then leave the capacitor as it was.

In general, I achieved that the B5-21 worked almost silently, like a computer.

The power transformer works silently, you can't hear it at all. When working with B5-21, I can note that the source, despite its weight and size, is very reliable and convenient. It is convenient to regulate the voltage with a step switch, adjust with a resistor. By the way, for prevention, the biscuit switch must be cleaned of dust with alcohol, lubricated with mechanical parts. Replace the resistor if it regulates the voltage abruptly.

Now about the protection of the source from short circuits. The REN-48 relay is responsible for protection. In my case, the protection stopped working when I cleaned the relay contacts from dust with alcohol. You need to carefully straighten the contact plates so that they are triggered when the output of the power supply is closed. Then everything will work. The response threshold is regulated by trimming resistors on the reverse side.

After preventive maintenance, the power supply will serve you for a long time. You can charge all kinds of batteries, power screwdrivers, various motors, radio circuits. The built-in voltmeter and ammeter are very convenient, they allow you to observe what current and how different circuits are consumed. Very well suited for the repair of car amplifiers, car radios, subwoofers, and other equipment operating up to 30 Volts. The source is well made, like all military things of the USSR. There is a power reserve, the current holds even more than the calculated one. You can convert it to a higher current. Now power supplies of this class are expensive, but this one cost me 1,500 rubles. plus, having made him preventive maintenance, he received a sufficiently powerful power supply in the ability to adjust the voltage and monitor.

Advantages:

1. Huge supply of power transformer in terms of power with the ability to increase it by using a more powerful stabilizer.

2. Reliability, the ability to work for a long time under load without overheating.

3. Simplicity of design, maintainability, survivability margin of the USSR - the military defense industry,

4. Stability of parameters of voltage, current, convenient functionality, monitoring.

Disadvantages: