Boiler pump control. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Boiler pump control. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Power Supplies

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The circuit performs the following functions:

turning on pump No. 1;
issuance of signals about the emergency stop of pumps;
switching pump #1 to pump #2 (if pump #1 stops);
exclusion of automatic reclosing in case of power failures.

Electrocontact pressure gauges (ECM) installed at the pump outlet are used as a sensitive element to control the operation of the pump.

The actuation pressure of the contact device is set, which is close to the working pressure in the pipeline. If the pump stops, the pressure drops, causing the circuit to operate. But this method is unreliable, since the pressure in the system can change for other reasons, which leads to false alarms (or non-operations).

They also use control over the contacts of a thermal relay. In this case, the possibility of controlling the operation of the pump as a whole is excluded, and only the pump drive (electric motor) is controlled.

In this scheme (see figure), it is proposed to use a flow switch as a sensitive element. If there is no flow, its contacts FS are closed. The circuit is started by pressing the SB2 button, which leads to the switching on of the K1 relay and the KM1 starter. The countdown begins with the help of the time relay K2 and K7. If pump No. 1 does not reach the nominal mode for the time set by relay K2, the starter KM1 is turned off by contacts K2.1, at the same time, time relay K2.2 is connected through contacts K3.

(click to enlarge)

Through contacts K3.1, relay K4 is turned on, which, with its contacts, turns on the starter KM2 and relay K5. From contacts K5.3, a signal is removed to turn off pump No. 1. Contacts K5.2 prepare relay K6 for operation. After relay K3 is deactivated, relay K6 is ready to receive a signal from contacts K2.2 through contacts K5.2 and K4.3, which means that pump No. 2 is stopped. Now, in case of repeated closing of contacts K2.2, relay K6 will operate, block itself with contact K6.1, open the power circuit of the starter KM2 with contacts K6.2 and give an alarm signal from contacts K6.3. The feedback between thermal relays and the circuit is mechanical.

The operation of the thermal relay (contacts T1 and T2) leads to the opening of the power supply circuits of the pump motor, which in turn leads to the closing of the contacts FS and the operation of the circuit.

The functional purpose of the relays included in the circuit:

K1 - protection against automatic reclosing in case of power failures;
K2 - suppression of the bounce of the contacts of the flow switch, shutdown of KM1;
K3 - time delay for turning on engine No. 2;
K4 - multiplication of contacts
K3, switching on KM2 and K5, protection against false positives K6;
K5 - issuing and storing the signal "pump No. 1 failure";
K6 - shutdown of KM2, issuance and storage of the signal "pump No. 2 failure"; K7 - control of the inclusion of pump No. 2.

The power circuits of pumps No. 1 and No. 2 are switched by the contacts of the starters KM1 and KM2, respectively. These circuits are not shown in the diagram.

The switching time of pump No. 1 to pump No. 2 corresponds to the difference between the time settings of relays K3 and K2. The time allotted for pump No. 1 to enter the operating mode corresponds to the time set by relay K2. The time allotted for pump No. 2 to enter the operating mode is determined by the ratio T2 = TK7 (TK2 + TK3), where TK7, TK2, TK3 is the response time of the relay K7, K2 and K3.

In this scheme, pump No. 1 is leading, pump No. 2 is driven. If necessary, a switch can be included in the circuit to select pump No. 2 as the leader, and pump No. 1 as the slave.

To do this, in the gap between the points AB; CD; .E and GH introduce a switch (from the PKU series) that provides contact closure in accordance with the table:

It is also possible to use an additional relay instead of a switch, which has four groups of contacts for switching. The winding of this relay can be switched by a toggle switch.

Details. Buttons SB1 and SB2 type KE. Relay K1, K4, K6 type RP21-003-220V, 50 Hz, K5 type RP21-004-220V, 50 Hz. Relay K2, K3, K7 type VL68. It is possible to use one electric machine relay of the VS-2 type instead of the K7 and K33 relays (however, I did not have the best impressions of this relay). Flow switch type A61KB Johnson Controll, but domestically produced flow switch can be used.

Author: P.Botsula

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