Method and circuit for monitoring the operating condition of electric motors

A circuit arrangement for monitoring the operational state of an electric motor, comprising:

• an angle encoder mechanically connected with an electric motor;
• a first processor electrically connected to said angle encoder, wherein said first processor comprises a first comparator that receives an output signal from said angle encoder;
• a second processor electrically connected to said angle encoder, wherein said second processor comprises a second comparator that receives said output signal from said angle encoder;
• and
• a shutoff component, wherein said shutoff component shuts off said electric motor should an error be detected in output signals from either one of said first and second comparators during a testing interval.

A method for monitoring the operational state of an electric motor, comprising:

• performing a first evaluation by comparing during a testing interval an actual number of revolutions of an electric motor with a stored number of revolutions which defines the stoppage of said electric motor;
• simultaneously and independently performing a second evaluation by comparing during said testing interval the actual number of revolutions of said electric motor with said stored number of revolutions;
• detecting a safe operational state for said electric motor if the actual number of revolutions lies above said stored number of revolutions in said first and second evaluations;
• and
• performing steps for producing a safe operational state for said electric motor if the actual number of revolutions lies below said stored number of revolutions in at least one of said first and second evaluations.

A circuit arrangement for monitoring the operational state of an electric motor, comprising:

• an angle encoder mechanically connected with an electric motor;
• a first processor electrically connected to said angle encoder, wherein said first processor comprises a first comparator that receives an output signal from said angle encoder and from a first memory;
• a first timer connected to said first comparator to compare said output signal from said angle encoder with an output signal from said first memory at a predetermined time after changing a torque current of said electric motor;
• a second processor electrically connected to said angle encoder, wherein said second processor comprises a second comparator that receives said output signal from said angle encoder and from a second memory;
• a second timer connected to said second comparator to compare said output signal from said angle encoder with an output signal from said second memory at a predetermined time after changing a torque current of said electric motor;
• and
• a shutoff component, which shuts off said electric motor in dependence on an output signal from either one of said first and second comparators.