Safety device, system and method for monitoring an electric motor

A safety device (10) for monitoring an electric motor (101), said electric motor (101) being connected to a power supply line (100) and being equipped with a drive shaft (102), characterized in that said safety device (10) comprises a control unit (12) having:

• detection means configured for being associated with said electric motor (101) to detect at least two physical quantities related to and associated with the operation of said electric motor (101), said at least two physical quantities being selected from the actual rotation speed of said electric motor (101), the voltage measured on said power supply line (100) and the frequency measured on said power supply line (100), wherein said detection means comprise at least one first input channel (16) configured to be connected to said power supply line (100) of the electric motor (101) in order to instantly detect the voltage on said power supply line (100) and to transmit at least one first work signal (W) correlated to said detected voltage to at least one first processing unit (17);
• signaling means configured to transmit a control signal (C) generated by said at least one first processing unit (17), wherein said signaling means comprise switching means (15) controlled by said at least one first processing unit (17);
• wherein said at least one first processing unit (17) is connected to said detection means and to said signaling means;
• wherein said at least one first processing unit (17) is configured to compare said at least two physical quantities with each other, which are related to and associated with the operation of said electric motor (101) in order to detect faults or anomalies and to generate said control signal (C) on the basis of said comparison;
• wherein said detection means further comprise:
• at least one second input channel (36) configured to be connected to said power supply line (100) of said electric motor (101) in order to instantly detect the voltage applied to said power supply line (100) and to transmit a second work signal (W′), correlated to said voltage detected, to at least one second processing unit (37) comprised in said device (10);
• wherein said at least one second input channel (36) comprises at least one second measurement unit (39) connected to said second processing unit (37) and second amplification means (38) configured to be connected to said power supply line (100) and to transmit to said second measurement unit (39) at least one second intermediate voltage signal (IV′) and at least one second intermediate frequency signal (IF′), said second measurement unit (39) being configured to measure said at least one second intermediate voltage signal (IV′) and said at least one second intermediate frequency signal (IF′) and to transmit said at least one second work signal (W′) to said second processing unit (37).