Method for detecting faulty operation of gas blower driven by DC motor

[0022] Figure 1 to Figure 3 The diagrams respectively show the fan characteristic curve and the equipment characteristic curve of the gas fan formed as a radial fan when various types of defects as influencing variables occur, where the ordinate is the boost dp and the abscissa is the delivery volume flow Vpkt.

[0023] figure 1 A schematic diagram exemplarily shows the defect that the air density changes. The device characteristic curve 10 (also called "system characteristic curve") is simply assumed to be constant. In addition, the reference characteristic curve 30 and the smaller air density characteristic curve 40 are respectively illustrated as reference variables at a constant rotation speed N.

[0024] figure 2 Shows the rising pressure loss based on system-related defects (such as blocked exhaust pipes on heating boilers or dirty heat exchangers). The system-related defects make the nominal equipment characteristic curve 10 change when the gas fan starts with the heating boiler. It has shifted to the left towards a smaller volume flow (characteristic curve 50) and is further away from the nominal device characteristic curve 10 (characteristic curve 60) during operation.

[0025] in image 3 In the figure, neither the equipment nor the environment is affected, but the figure exemplarily shows the reduction in efficiency of the motor of the gas fan due to heat generation as a defect type. Here, the device characteristic curve 10 remains constant. The reference characteristic curve 70 also remains unchanged at a constant speed N.

[0026] Figure 1 to Figure 3 The effect of the defect types shown in the example on the current consumption I of the DC motor of the gas fan is shown in Figure 4 In the figure. The curve 80 shows the maximum allowable current consumption related to the change of the rotation speed N when the DC motor is operating in an unsteady state (that is, during acceleration or during the increase of the fan speed of the gas fan). This current limit is implemented on the electronic components of the motor and is used, for example, to prevent excessive current and limit the speed when the DC motor is blocked. In quasi-steady state operation, the constant current consumption at a constant speed N is smaller. The characteristic curve 90 is a reference characteristic curve related to this. according to figure 1 The air density decreases and according to figure 2 The two types of defects caused by blocked exhaust pipes cause a smaller current at the same rotation speed N_ref. On the contrary, the heating of the DC motor and the resulting decrease in efficiency lead to an increase in current consumption at the same rotation speed N_ref. The characteristic curve 110 is based on figure 1 The type of defect, the characteristic curve 120 represents the figure 2 Type of defect, characteristic curve 130 represents image 3 The type of defect.

[0027] Figure 5 Show for example in accordance with image 3 The comparison chart of the quasi-steady-state characteristic curve 98 of the current consumption I of the DC motor under the defect condition and the reference characteristic curve 95 determined by laboratory technology. Two offset characteristic curves 82 and 85 are provided around the reference characteristic curve 95, which define the tolerance range. The range 200 with a higher current consumption I at the same rotation speed N_ref and the range 300 with a smaller current consumption I at the same rotation speed N_ref are outside the tolerance range. Once the characteristic curve 98 intersects the characteristic curve 85 and the DC motor runs in the range 200 outside the tolerance range, an alarm and defect code is output. The figure only shows according to image 3 The type of defect, when it appears according to figure 1 or figure 2 The characteristic curve 98 will enter the range 300 when the defect type is selected. Alarm and/or defect codes are also output at this time.

[0028] Image 6 It is exemplarily shown in a schematic diagram that the current consumption value of the DC motor at a constant rotation speed N relative to the reference value slowly changes with the passage of time t. The dashed line 150 forms a reference value. The actual continuously measured current consumption 140 fluctuates only slightly and may be within a tolerance range, but it decreases significantly over time, as shown by the average line 160. When the current consumption value is too far away from the reference line 150 for a long time, an alarm and defect code will also be output.

[0029] The plausibility test of comparing the measured current consumption with the reference value of the reference value characteristic curve is performed directly through the electric motor electronic components of the gas fan. To this end, the motor electronic components also have a current measuring device and an electronic control module (especially a comparator), but it is not limited to this.

[0030] At the motor electronic components, while monitoring the overcurrent by the comparator in the microcontroller, the motor current (current consumption) is applied to the analog/digital converter (ADC) of the microcontroller. Use a shunt to measure the motor current. Then the signal is tapped and converted in the middle of the PWM cycle (PWM = pulse width modulation). In addition, when necessary, the intermediate circuit voltage is measured and the motor current is used to calculate the motor efficiency.

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