Sklopnici (Contactors): devices, parts and more

• The topic is Sklopnici (Contactors), a device with energetic (remote) activation of moving contacts via electromagnet or pneumatics

General info

• It is a special type of switch, able to switch in normal operation and in overload
• If it can switch remotely, it is called a remote switch

Parts of a contactor:

• Main
• Auxiliary
• Magnetic coil for control
• Arc extinguishing chambers

Types of contactors:

• Auxiliary contactors used for switching control circuits
• Main contactors
• Smaller contactors are for currents up to 25 A
• Larger ones are for currents of 2500 A and voltages of 1 kV ~, 1.5 kV=
• Contactors enable 3,000 switches per hour

Basic contactor data:

• Nominal voltage
• Rated current (or power)
• Rated thermal capacity, i.e., the maximum current the contactor can conduct during 8-hour operation
• Contactors require a pre-fuse device for short-circuit protection

Connection markings of main contactors:

• Connection of the coil (A1, A2)
• Main contacts: 1, 3, 5, 2, 4, 6
• Auxiliary contacts: 13, 21, 14, 22

Contact functions:

• Disconnecting
• Connecting
• Alternating

Coil types:

• Single winding with markings A1 and A2
• With a tap: A1, A2, A3
• Double winding: A1, A2, B1, B2

Applications of contactors:

• Installation contactors for lighting, heating, etc
• Motor contactors

Relays and auxiliary contactors:

• A relay is a device that, depending on the change of a physical quantity, causes changes in the same or another electrical circuit

Types of relays:

• Measuring relays: measure the operating quantity and open and close contacts, use primarily for protection
• Auxiliary relays: are similar to measuring ones, but smaller in size, intended for use in auxiliary circuits
• Time relays: used to set the triggering time

Relay and contactor contacts:

• Connecting
• Disconnecting
• Alternating
• Instantaneous (connecting-disconnecting)

Bimetallic relays:

• Bimetallic relays are overcurrent thermal relays with a current-dependent characteristic based on the heating of a bimetallic strip

Bimetallic relays exist with:

• Classic mechanical current protection design
• Electronic current protection design for larger currents

Installation switches:

• Installation switches are used to switch devices on and off
• They connect, continuously conduct and break currents of normal operation and possible overloads

They can briefly conduct short-circuit current

• Mode of operation: Installation switches can work with
  • Position - without restoring force, manual switching on and off, lever, cam, hinged
  • Impulse - with restoring force (button for staircase lighting)
  • Locking (automatic switch)

Types of drives:

• Manual
• Mechanical

Arc extinguishing methods:

• Air
• Oil
• Magnetic
• Vacuum

Purpose of installation switches:

• Protective
• Command
• Limit (pressure, level switches)
• Auxiliary

Installation switches:

• Buttons can be hinged, rotary, pressure, or pull

Installation switches:

• Mostly used for lighting control: 230V, 50-60 Hz in a three-wire single-phase system (L, N, PE conductors).

Installation types:

• Flush-mounted
• Surface-mounted
• Built into devices

Connection methods:

• Single-pole
• Double-pole
• Series
• Alternating
• Cross

Installation switches:

• General version - IP 20 or IP 40
• Waterproof version - IP 44, IP 65, mostly IP 55

Installation

• Installation switches are always connected to the phase conductor
• The threaded part in the lamp socket, into which the bulb is screwed, must not be connected to the phase conductor - the phase conductor is connected to the central contact of the socket
• The switch can interrupt the neutral conductor, but this must be simultaneous with the phase, or after the phase is interrupted

During switch-on:

• Reverse order
• The protective conductor is connected to the housing
• Switches are 1.5 m from the ground, and pull switches are 2.25 m from the ground

Switchgear (devices) - are devices used to close and open electrical circuits

• Some can switch on and off certain currents of normal and abnormal operating conditions, while others cannot
• Used for establishing, maintaining and interrupting the continuity or discontinuity of electrical circuits

Switches:

• Used for switching, continuous conduction and interruption of normal operating currents and possible overloads, and can also conduct short-circuit currents very briefly
• Circuit breakers can switch on, conduct and switch off currents up to the limit values of the short-circuit current

Disconnectors

• Disconnectors have the task of creating a separating gap that will ensure the safety of personnel and equipment
• They are used for opening and closing energized electrical circuits and can continuously conduct a current of normal operation
• They can withstand a short-circuit current for a short time interval and are mainly used in switchgear

Starters:

• Serve to start motors or start other equipment and allow operating parameters to remain within specified limits
• Regulators allow some operating or working values to remain at approximately constant values

Fuses:

• Automatically interrupt the electrical circuit when the current exceeds the permissible value

Surge arresters:

• Used to protect electrical installations from surges and are usually connected between electrical conductors and earth
• They limit the level of surge voltages
• Relays are devices that measure an operating quantity (current, voltage, pressure, temperature,...) and, at a certain value, automatically close or open their contacts, thus enabling the control of further devices
• A relay is a type of command switch
• Connection devices (accessories) are types of switchgear whose parts for connection and separation are not rigidly fixed on one base (sockets and plugs)
• It can be said that in electrical installations they also play a role similar to disconnectors
• Switch blocks are actually groups of different switchgear, and are most often placed in distribution cabinets, control tables, etc

Switchgear - according to rated voltage:

• Low voltage - up to 1000 V
• High voltage - over 1000 V

Terms related to switchgear:

• The pole of a device is the part of the switchgear that belongs to one active conductor of an alternating system or one polarity of a direct current system
• Actuation or activation current is the amount of current that must flow for a certain time after which the switchgear operates
• The protective element is a switchgear that switches off an electrical circuit upon the occurrence of a specific harmful stimulus
• The button is a switchgear used for manual short-term connection or disconnection of contacts
• Release is part of a switchgear that, when a certain electrical magnitude (less often some other physical magnitude) changes, releases the accumulated energy required to close or open the contact
• The energy is most often accumulated in a tensioned spring or compressed air
• In switchgear, overcurrent (bimetallic or electromagnetic), undervoltage and voltage releases are most commonly encountered
• Making capacity is the highest peak value of the current that the device can switch on with a certain voltage and under certain operating conditions without welding of the contact elements and mechanical distortion
• Breaking (switching) power is the effective value of the current that the device can break with a certain voltage and power factor, and without the occurrence of a arcing effect between the contacts