Protection of power semiconductor components

1. A method for protecting the power semiconductor components used in the power stages of power electronics devices, such as frequency converters,

which uses calculation modeling the degree of heating of the semiconductor junction of the power components (V 11 –V 16 ), wherein the degree of heating of the power components between the measurable outer surface or cooler and the internal semiconductor junction is determined on the basis of the dissipation power and a thermal network model of the component,

wherein the temperature of the outer surface of the power component or the temperature of the cooler is measured,

wherein the modeled temperature of the semiconductor junction is the sum of the measured temperature of the outer surface or cooler and the calculated degree of heating, and

wherein, based on the modeled junction temperature, an alarm is issued or some other protective action is taken,

characterized in that, in the method:

the temperature of the semiconductor junction is calculated in real time, at least at time intervals equal to the shortest time constant in the thermal network model, on the basis of the heating caused by the dissipation power pulse produced during each current conduction cycle (t C ).

2. A method according to claim 1 ,

characterized in that, in the method

the variations of the semiconductor junction temperature (heat cycles) are monitored, their number is compared to maximum numbers of cycles specified by the manufacturer and fed into the control system, and an alarm is issued or some other protective action is taken when the number of cycles reaches the full count.

3. A method according to claim 1 ,

characterized in that, in the method:

calculation of the degree of heating is carried out at constant calculation intervals (t s ), the length of which is at least equal to the shortest time constant in the thermal network model.

4. A method according to claim 1 ,

characterized in that, in the method:

during the calculation interval (t s ), the dissipation power of the power semiconductor is assumed to remain constant (P EST ), where the dissipation energy (P EST *t s ) caused by the said dissipation power is the same as the actual dissipation energy (E COND ) calculated on the basis of the response characteristics of the power component during the same calculation interval.

5. A method according to claim 1 ,

characterized in that, in the method:

the calculation of changes in the degree of heating is based on the use of coefficients (k 1 , k 5 ) calculated beforehand and tabulated in the control system, which coefficients have been calculated on the basis of power semiconductor-specific time constants and the constant calculation interval.

6. A method according to claim 2 ,

characterized in that, in the method:

during the calculation interval (t s ), the dissipation power of the power semiconductor is assumed to remain constant (P EST ), where the dissipation energy (P EST *t s ) caused by the said dissipation power is the same as the actual dissipation energy (E COND ) calculated on the basis of the response characteristics of the power component during the same calculation interval.

7. A method according to claim 3 ,

characterized in that, in the method:

the calculation of changes in the degree of heating is based on the use of coefficients (k 1 , k 5 ) calculated beforehand and tabulated in the control system, which coefficients have been calculated on the basis of power semiconductor-specific time constants and the constant calculation interval.

8. A method according to claim 4 ,

characterized in that, in the method:

the calculation of changes in the degree of heating is based on the use of coefficients (k 1 , k 5 ) calculated beforehand and tabulated in the control system, which coefficients have been calculated on the basis of power semiconductor-specific time constants and the constant calculation interval.

9. A system (CU) for controlling the power semiconductor components used in the power stages of power electronics devices, especially frequency converters,

which uses calculation modeling the degree of heating of the semiconductor junction of the power components (V 11 –V 16 ), wherein the degree of heating of the power components between the measurable outer surface or cooler and the internal semiconductor junction is determined on the basis of the dissipation power and a thermal network model of the component,

wherein the temperature of the outer surface of the power component or the temperature of the cooler is measured,

wherein the modeled temperature of the semiconductor junction is the sum of the measured temperature of the outer surface or cooler and the calculated degree of heating, and

wherein, based on the modeled junction temperature, an alarm is issued or some other protective action is taken,

characterized in that it

calculates the temperature of the semiconductor junction in real time, at least at time intervals equal to the shortest time constant in the thermal network model, on the basis of the heating caused by the dissipation power pulse produced during each current conduction cycle (t C ).

10. A system according to claim 9 ,

characterized in that it

monitors the variations of the semiconductor junction temperature (heat cycles), compares their number to maximum numbers of cycles specified by the manufacturer and fed into the control system, and issues an alarm or performs some other protective action when the number of cycles reaches the full count.

11. A control system according to claim 9 ,

characterized in that the frequency converter or equivalent has a display, on which display the temperature of the semiconductor junction of an individual power component can be indicated directly in degrees.