FI81001B - Electric sauna stove - Google Patents

Description

Electric heater 81001

The invention relates to an electric heater to be connected to a three-phase network, comprising a star-connected and neutral conductor set 5, three-phase clock and thermostat control switches for controlling the power supply to the resistors, a switch and a room temperature thermostat for supplying power to at least one resistor past the clock switch.

10 Finnish advertisement publication No. 74610 discloses an electric heater suitable for room heating. The publication proposes to supply electricity either to a separate resistor or to a single star-connected resistor via a separate switching device. Most preferably, two or three of the resistors in the star-connected series of resistors are connected in series so that a phase voltage is applied across the entire series while the normal star connection is disconnected. The series connection of two resistors gives half of the heating power of one resistor and the series connection of three resistors gives one third of the heating power of one resistor. For example, in the case of a 6 kW 20 heater, a series connection of two resistors gives a room heating power of 1000 W. However, this is usually too high a power, which makes the heating control heavily sawn. The series connection of three resistors to room heating is again a rather complex connection and requires a complex main switch.

Swedish Patent Publication No. 308419 discloses another star connection of heater heating resistors suitable for room heating. Here, the electricity is supplied by a special thermostat 30 which switches on the first two stages as the temperature difference increases and on the third stage as the difference increases further. Here, if the temperature setting range of the thermostat extends to the room temperature range, then the entire heating takes place by connecting two resistors in series between two phase conductors, which the thermostat cuts off according to the temperature difference. Here, however, the room heating power is unnecessarily high despite the series connection of two resistors.

2 81001

The object of the invention is to provide an electric heater with a new type of electrical connection, which is suitable for heating a sauna room. Special attention has been paid to the simplicity of the connection and the optimal room heating efficiency. The characteristic features of the invention are set out in claim 1. It should be noted that in practice the heating power of one resistor drops more than could be inferred from the power supply time. This is because the impedance of the heating resistor is not only composed of a receptive part but also includes an inductive part. This inductive part has a remarkably strong effect when breaking the sine wave into periodic parts. A particularly preferred embodiment is set out in claim 2. Extreme simplicity in connection technology has been achieved here.

15

In the following, the invention is illustrated with reference to the accompanying figures, which show the principles of the invention and an embodiment of the connection.

Figure 1 shows the power supply with a delayed trigger.

Fig. 2 shows a half-wave rectified power supply. Fig. 3 shows a wiring diagram for an electric heater. 25 The thyristor and triac components make it possible to switch on the power supply in the middle of the period, in which case the power supply of the room heating resistor A voltage is applied to the heating element at the end of each half-cycle, in which case the power supply is as shown in Figure 1. The supplied heating power 30 is represented by surfaces 2. In the case of Figure 1, the heating power is a fraction of the nominal power of the resistor. With triac and thyristor components, the power supply can be arbitrarily adjusted from zero to rated power. However, these components require their own control unit, which makes the wiring diagram complex.

35 However, a room temperature thermostat can be built into this control unit, thus avoiding a separate power switch.

3,881,001

Figure 3 shows a circuit diagram of an electric heater according to the invention. The three-phase voltages L1, L2 and L3 are applied via a plurality of switches to a star-connected series of resistors formed by the heating resistors 5L1, 5L2 and 5L3. · The zero conductor N is connected to the common end of these resistors. In practice, the temperature limiter 6 and the thermostat 7 form a common unit in which the switches of the temperature limiter and the thermostat are arranged in series. The heater is switched on normally by means of a clock device 8, which at the same time limits the maximum on time to four 10 hours (in Finland).

The heater can be used as a room heater by applying a half-wave rectified phase voltage to one resistor 5L3. For this purpose, the room temperature thermostat 9 and the diode 10 are connected in series so that they bypass the corresponding switch of the clock device 8. Room temperature thermostat 9 includes two tips; others turn off the room heating and the other is used for the actual thermostat control. Figure 3 shows the switches in room heating mode when the room heating thermostat has temporarily switched off the heating current.

The sauna temperature thermostat 7 does not cause a disadvantage in room heating operation, as its switches are closed in the room temperature range.

In practice, controlling one 2 kW resistor in a 6 kW heater with a half-wave rectified voltage reduces the heating power by more than half of the original heating power. This is due to the fact that the heating resistor also has an inductance in place of the resistive part, the significance of which in the half-wave rectified current is considerably greater than that of the constant sine wave current. In practical measurements, a 2 kW resistor has given a half-wave rectified current of about 850-950 W. When a half-wave rectified electric current is passed through one of the 35 resistors, the power supply is as shown in Figure 2. Only the positive part of the voltage 1 is applied to one heating resistor, whereby the surfaces 3 represent the input power.

Claims (2)

4 81 001 1. An electric booster set for a three-way switch, a single power supply for the power supply and zero (N) means a series of circuits (5Li, 5L2 / 5L3) , copying and rumming thermostats (9) for measuring the output of the output (5) hela perioden. A three-phase mains-operated electric heater comprising a star-connected and neutral-conductor (N) 5 resistor set (5li, 5L2 '5L3) * three-phase switches controlled by a clock device (8) and a thermostat (7) for controlling the power supply to the resistors, a switch and a room temperature thermostat (9) one resistor (513) past the switch of the clock device (8), characterized in that the heater comprises 10 switching devices (10) for supplying power in room heating only periodically for part of the whole period. Electric heater according to claim 1, characterized in that said switching device (10) is a diode connected in series with the switch of the second thermostat (9) and through which the half-wave rectified phase voltage is passed to the corresponding resistor past the switch controlled by the clock device (8). 20 Patentkrav 2. An electrical circuit according to claim 1, which comprises a diode, 10 light emitting diodes, 35 flashing diodes and a series of high-voltage and long-term thermostats (9) copying and genome flashing circuit förbi den av klockanordningen (8) styrda koppiingen. Il