Control and protection

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DC-power supply Siemens 6EP33337SB000AX0 AC/DC Spring clamp connection IP20
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DC-power supply Siemens 6EP33337SB000AX0 AC/DC Spring clamp connection IP20

€87.48 +VAT
PLN 410.89
  • Manufacturer: Siemens
  • Manufacturer Code: 6EP33337SB000AX0
  • EAN: 4025515155164
  • Voltage type of supply voltage: AC/DC
  • Type of electric connection: Spring clamp connection
  • Degree of protection (IP): IP20
  • Max. output current 1 [A]: 5
  • Nominal value output current 1 [A]: 5
Response time: usually up to 1 day
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Control and protection

Control and protection in drives and machines is crucial for the proper functioning of systems and equipment driven by electric motors. The use of a number of components working with electric motors allows for effective control and protection of their operation. Possible damage to an electric motor is eliminated by using inverters and braking resistors in their control systems.

Control and protection - benefits

Electric motors are the main elements converting electrical energy into mechanical energy. In some systems the machines are driven by traditional motors supplied with AC or DC voltage. In the group of AC motors there are single-phase, three-phase and double-phase powered motors. In this group there are synchronous motors and asynchronous motors. They are characterized by high efficiency and low purchase costs. As driving devices, they do not require precise control.

They are used in industry and production line automation. They are used to drive mains-powered vehicles such as trams, trolleybuses and electric locomotives. They are used in elevators, cranes and port cranes. Their construction and cooperating braking resistors enable them to function as a braking system in driven machines and devices.

Lines using asynchronous drives are less susceptible to damage to the electric motor because of its simpler construction. Squirrel-cage (asynchronous) motors are built from two basic elements, which are a moving rotor and a fixed stator. In contrast to the traditional motor in this case, the additional voltage is not transmitted to the rotor through the brush system. In the case of an asynchronous motor, the voltage applied to the stator creates a magnetic field, forcing it to work and converting the energy into rotational movement of the rotor. As a result of asynchronous motor operation, the effect of rotor slip occurs. It consists of delayed work of rotating element in relation to the stator. This value increases with increasing speed and is on average between 2 and 4%.

Devices supporting asynchronous motors

The operating characteristics of squirrel-cage asynchronous motors require the use of an appropriate type of associated equipment. The use of these devices allows appropriate control and protection as well as correct operation and safety. Asynchronous motors are protected against large voltage surges in the network by using proper inverters and cooperating with them ripple resistors. During start-up, the asynchronous motor loads the mains several times higher power consumption than the rated value which is maintained during operation.

Collaborative systems prevent the occurrence of failures and protect against overheating of motors. They ensure that the correct value of current is applied to the stator and the programmed parameters of the motors are maintained. This suitable control and protection enables asynchronous motors to be used in a wide range of equipment and construction machines. Low- and medium-power asynchronous motors are used in pumping systems, conveyor belts, industrial ventilation systems, crushers and shredders in construction, as well as to drive many other small machines.

Control and protection - inverters - frequency converters

One of the basic devices responsible for the control and protection of squirrel-cage motors are inverters. They reduce or increase the frequency of the voltage supplied to the motor stator. In doing so, they regulate its operating characteristics and direction of movement. These complex devices also regulate the voltage according to the increase or decrease of the current frequency. The principle of the asynchronous motor is to delay the reaction of the rotor and its rotary motion by a few percent in relation to the magnetic field created inside the stator.

Inverters, often called inverters, fall into two categories and two subgroups:

  • scalar inverters - are used for simple devices that do not require precise control, such as pumps or fans,

  • vector inverters - there are versions with a rotational speed measurement sensor. They enable precise control of motor operation parameters,

  • three-phase motor inverters - have 3 inputs and 3 phase outputs. They are used for devices of higher power up to 500 kW,

  • inverters for single phase motors - have 3 230V outputs, mostly used in devices with power outputs of a few kilowatts.

To minimise the possibility of motor failure or overheating during start-up, at the peak of current consumption, a star system is used. This consists of switching the order of the motor windings and switching to a delta system and vice versa, depending on the operating status of the device. Such a system ensures safe operation and economical functioning of the system. In these systems, it must be ensured that the work load of the motor is relieved at the time of starting, so that there are no forces that reduce its starting torque. Damage to the electric motor is reduced to a minimum with these controls. In domestic applications, inverters are used to drive washing machines, drills and ventilation equipment.

Braking resistors - boosters

The risk of damage to the electric motor is drastically reduced when using brake resistors in the motor control system. They support bidirectional operation of asynchronous motors. In high power systems and machines, the kinetic forces acting during operation are very high. The brake resistors convert the excess energy generated by the motor into heat energy. This energy is then released by appropriately selected components. The parameters and current values must be individually matched to the system in which the braking resistor will operate.