Method for starting an electronic drive circuit of an electric motor and circuit arrangement therefor

A method for starting an electronic drive circuit for the windings of an electric motor, said drive circuit having input terminals and being a part of a circuit arrangement further including a voltage source having first and second connecting terminals and a system switching element;

• each of said windings having first and second coil ends and said drive circuit including a first plurality of power switches connecting corresponding ones of said first coil ends to said first connecting terminal of said voltage source and a second plurality of power switches connecting corresponding ones of said second coil ends to said second connecting terminal of said voltage source;
• a control unit connected to said voltage source;
• a capacitor having a capacitor voltage (UC) and being connected via said system switching element to said connecting terminals of said voltage source;
• said capacitor being connected to said input terminals parallel to said drive circuit;
• and, an operating circuit for said system switching element;
• the method comprising the steps of:
• for starting said motor, closing said system switching element and charging said capacitor;
• opening said system switching element after charging said capacitor;
• causing said control unit to start a test step for said drive circuit;
• supplying said drive circuit exclusively from said capacitor voltage (UC) during said test step;
• and,
• said test step being a test step of a test cycle having a plurality of test steps;
• causing said control unit to monitor said capacitor voltage (UC);
• making a decision of whether the executed test step of the test cycle is fault free or defective based on a change of said capacitor voltage (UC) during one of said test steps of said test cycle in dependence upon the executed test step;
• after opening said system switching element in one of said test steps, applying a load to said capacitor;
• if said capacitor voltage (UC) drops off, evaluating said system switching element as being free of fault;
• and,
• if said capacitor voltage (UC) is approximately constant, evaluating said system switching element as being defective;
• in one of said test steps, closing at least one of said power switches of said first plurality;
• holding open all of the power switches of said second plurality of power switches;
• and,
• evaluating said capacitor voltage (UC).

A method for starting an electronic drive circuit for the windings of an electric motor, said drive circuit having input terminals and being a part of a circuit arrangement further including a voltage source having first and second connecting terminals and a system switching element;

• a control unit connected to said voltage source;
• a capacitor having a capacitor voltage (UC) and being connected via said system switching element to said connecting terminals of said voltage source;
• said capacitor being connected to said input terminals parallel to said drive circuit;
• and, an operating circuit for said system switching element;
• the method comprising the steps of:
• for starting said motor, closing said system switching element and charging said capacitor;
• opening said system switching element after charging said capacitor;
• causing said control unit to start a test step for said drive circuit;
• supplying said drive circuit exclusively from said capacitor voltage (UC) during said test step;
• and,
• said test step being a test step of a test cycle having a plurality of test steps;
• in a first one of said test steps, checking the operation of said system element;
• in a second one of said test steps, checking the connection to chassis ground of one of said power switches;
• and,
• in a third one of said test steps, checking the proper connection of said windings.

A circuit arrangement comprising:

• an electronic drive circuit for electrically operating a motor;
• a voltage source having connecting terminals;
• said drive circuit having input terminals connected to corresponding ones of said connecting terminals of said voltage source;
• a capacitor connected to said connecting terminals of said voltage source parallel to said input terminals of said drive circuit;
• a system switch element arranged between one of the connecting terminals of said voltage source and one of said input terminals of said drive circuit and said capacitor;
• an operating circuit for actuating said system switch element;
• a control unit for starting a test step for said drive circuit;
• said capacitor being adapted to hold energy required for carrying out said test step;
• and,
• means for causing said energy to be supplied to said input terminals of said drive circuit exclusively from said capacitor during a test cycle.