Calculation of shop power supply

Contents

Introduction

Task

1. Determination of electric heater power

2. Thermal calculation of heating elements

3. Fan selection and motor power determination

for its drive

4. Calculation of heating device design parameters

5. Connection network calculation, control equipment selection

and protection

6. Development of electric heating plant control scheme

List of literature used

Task

The following data is selected according to the code of the credit book:

• number of pig heads N = 100 goal;

• specific volume of the room V0 = 10 m/goal;

• fan air head H = 600 N/m2;

• indoor temperature = 19 ° С;

• average outside air temperature = 27 ° С;

• average temperature for heating period = 2.2 ° С;

• thermal characteristic of the room q0 = 2.8 kJ/( m );

• sows of heavy-thrust breeds, live mass of 200 kg;

• location of TENs in the heating unit - corridor.

6 Development of control diagram of electric heating plant

The electric heating plant control diagram shall provide:

• plant operation in manual and automatic modes;

• light alarm: voltage supply;

operation of each section of the electric heater; "calorifer on"; "emergency heating of the heater"; emergency shutdown of the plant in case of overheating of TENs;

• protection of electric motor and heating elements of heater from

short-circuit currents;

• switching off and on of installation by air temperature sensors in

room.

Automatic control of the heating and ventilation plant shall provide for sectional switching on and off of the electric heater in automatic and manual modes.

The heating elements of the heater cannot be switched on when the fan is not working.

Control of indoor air temperature is carried out using the temperature controller PTR2, the action of which is based on a change in the resistance of semiconductors from temperature.

Control circuit provides automatic and manual operation modes. In automatic mode, the universal switch SA1 is set to position A. The coil of the magnetic starters KM1KM3 is powered and all three sections of the heating elements of the heater are turned on, as indicated by the lamps HL2HL4.

When the temperature of the air in the heated room is higher than the set one, the temperature controller KM6 operates, opens its contacts in the coil circuit of the magnetic starter KM1, which turns off one section of the heater.

If the temperature continues to increase, the temperature controller KM6 denies power to the magnetic starter KM2, which stops the second section. The third section operates similarly.

KK3KK5 regulators protect the heaters from overheating by opening their contacts in the KM1KM3 magnetic starter circuit when the temperature on the surface of the heating elements exceeds 180 ° C. In this case, the heating elements stop working, and when the temperature decreases, they turn on again. The heaters can be activated only after the fan is switched on by the QF2 circuit breaker, the block contacts of which are in the control circuits of the KM4 magnetic starter.

In manual mode, the switch SA1 is set to position P, and the operation of the heating sections of the electric heater is controlled using the key SA2: in position 1, the first section of the heater is turned on, in position 2, the first and second, in position 3 - all three sections.