Safety drive for a flap or a valve

A method for the assured return of a flap or of a valve for controlling a gas or fluid volume flow, into a predetermined position if a voltage failure or voltage drop occurs, with a safety drive having a safety circuit for returning into a predefined safety position a flap or a valve for controlling a gas volume flow or fluid volume flow, the safety drive comprising:

• an actuator drive with a controllable electric motor;
• a power feed for the electric motor;
• a capacitive energy store;
• and
• a controllable power assembly which either charges the capacitive energy store from the power feed or discharges said capacitive energy store into the electric motor in order to operate the electric motor, the power assembly comprising a first controllable switch and a first diode which by passes said first controllable switch, and comprising a second controllable switch with a second diode which by passes said second controllable switch, the first and second controllable switches being connected in series, wherein a series circuit of the capacitive energy store and an inductor is connected between a pole of the intermediate circuit and the connection point of the first and second controllable switches, the method comprising the steps of:
• in normal operation, converting an electric current which also feeds the electric motor to a reduced voltage potential by means of the power assembly acting as an energy converter in a step-down mode;
• and storing electrical energy in the capacitive energy store, and
• if a voltage drop occurs below a predetermined value or a voltage failure occurs, converting the electrical energy stored in the capacitive energy store back to an increased voltage potential by means of the same power assembly in a step-up mode, and the converted energy to operate the electric motor until the predefined safety position is reached.

A safety drive having a safety circuit for returning into a predefined safety position a flap or a valve for controlling a gas volume flow or fluid volume flow, the safety drive comprising:

• an actuator drive with a controllable electric motor,
• a power feed for the electric motor,
• a capacitive energy store comprising at least one capacitor,
• a controllable power assembly which either charges the capacitive energy store from the power feed or discharges said capacitive energy store into the electric motor in order to operate the electric motor, and
• a monitoring unit which is assigned to said capacitor, the monitoring unit comprising a bypass series circuit composed of a resistor and a controllable switch, the monitoring unit being configured to individually check the functional capability of said capacitor by measuring the capacitance and the internal resistance of said capacitor.

A method for the assured return of a flap or of a valve for controlling a gas or fluid volume flow, into a predetermined position if a voltage failure or voltage drop occurs, with a safety drive having a safety circuit, the safety drive comprising:

• an actuator drive with a controllable electric motor,
• a power feed for the electric motor,
• a capacitive energy store comprising at least one capacitor,
• a controllable power assembly which either charges the capacitive energy store from the power feed or discharges said capacitive energy store into the electric motor in order to operate the electric motor, and
• a monitoring unit which is assigned to said capacitor, the monitoring unit comprising a bypass series circuit composed of a resistor and a controllable switch, the monitoring unit being configured to individually check the functional capability of said capacitor by measuring the capacitance and the internal resistance of said capacitor,
• the method comprising:
• in normal operation, converting an electric current which also feeds the electric motor to a reduced voltage potential by means of the power assembly acting as an energy converter in a step-down mod;
• and storing electrical energy in the capacitive energy store,
• if a voltage drop occurs below a predetermined value or a voltage failure occurs, converting the electrical energy stored in the capacitive energy store back to an increased voltage potential by means of the same power assembly in a step-up mode, and using the converted energy to operate the electric motor until the predefined safety position is reached, and
• checking the functional capability of the at least one capacitor periodically and individually by measuring the capacitance and the internal resistance of said capacitor.