Principle of operation of magnetic actuators of the PAS series
The magnetic actuator represents the starting device consisting of the contactor who is usually placed in the protective koyozhukh, managed remotely by means of buttons of management. The majority of magnetic actuators has the elements of thermal protection which are built in two or three phases in the form of the thermal relay which protects the engine from the overload.
Alternating-current magnetic actuators generally prednaznayochena for remote control of three-phase asynchronous electric motors with the short-circuited rotor.
Irreversive and reverse magnetic puskayotel are produced:
The irreversive magnetic actuator is intended for control of the electric motor without the possibility of change of the napravyoleniye of rotation; it consists of one contactor.
The reverse magnetic actuator gives the chance to change the electric motor rotation sense. In the reverse magnetic actuator there are two contactors, nearby, for "direct" and "return" inclusion. Contactors of the reverse magnetic actuator mechanically or electrically are blocked among themselves (often mechanical and electric blocking osushchestyovlyatsya at the same time - for bigger reliability) so that at inclusion of one of contactors of the second surely was отключен.
Magnetic actuators reliably work at mains voltages of 85 — 105% of rated value. All magnetic actuators of the spoyosobna to protect the engine from undervoltage and as the sledyostviye, from self-starting. Shutdown of the magnetic actuator proyoiskhodit at undervoltage in network up to 35 — 40% of nominalyyony value.
Magnetic actuators of the PAS series on the power of the managed electric motors are separated into 4 sizes: the 3rd size (at the voltage of 380 V) — 17 kW, the 4th size — 28 kW, the 5th size — 55 kW, the 6th size — 75 kW.
Designation of the magnetic actuator represents its uslovyony characteristic (by means of digits). After letters, oboznayochayushchy the series (for example, PAS), is put by dashes and digits: the first digit designates the size (dimension) of the magnetic actuator; vtoyory digit — execution on protection against environmental activity (1 — open; 2 — protected; 3 — pylevodoneproniyotsayemy); the third digit — execution to destination and to availability of thermal protection (1 — irreversive without thermal relay; 2 — irreversive with the relay; 3 — reverse without relay; 4 — reveryosivny with the relay).
Example of designation: PA-324 represents the magnetic actuator of the PASES series of the 3rd size (17 kW at 380 V), the protected execution, reverse with thermal protection.
Magnetic actuators are used to the remote upravyoleniye and protection (together with safety fuses or vozyodushny automatic machines) electric motors usually with power up to 75 kW. At the power of electric motors more than 75 kW применяется contactors in the combination with the relay or air automatic machines.