home · Measurements · Crane electric motor mtn, mtf with phase rotor. Asynchronous electric motor with wound rotor

Crane electric motor mtn, mtf with phase rotor. Asynchronous electric motor with wound rotor

Application area

Crane (or, as they are also called, crane-metallurgical) electric motors are widely used in the construction, energy, mining and metallurgical industries. The main purpose of crane electric motors is to provide reliable operation drive of crane and other mechanisms operating in short-term and intermittent modes, as well as for driving mechanisms operating with frequent starts and electric braking (tower, portal, gantry, bridge cranes, elevators and various lifting mechanisms).

Electric motor design

Crane electric motors of the MT series (MTF, MTH, MTI) are manufactured with a wound rotor, electric motors of the MTK series (MTKF, MTKH, MTKI) are manufactured with a squirrel-cage rotor.
The range of crane electric motors (with squirrel cage and wound rotors) includes more than 80 standard sizes with rotation axis heights from 112 to 280 mm.
All crane electric motors are manufactured as standard for moderate climates (climatic version U1), and also, at the request of the customer, can be manufactured for operation in tropical climates (climatic version T1) and for operation in northern latitudes(UHL version). All crane electric motors are due to design features capable of working in “hot” shops of metallurgical plants.
The engines are cooled using external airflow (IC 0141). The standard degree of protection of crane electric motors is IP44, the degree of protection of the terminal box and hatch of the slip rings of electric motors is IP 54.

An example of a symbol for a crane electric motor:

4MT K N 280L 10 U1

  • 4MT- electric motor series (4MT,MT)
  • TO- electric motor with a squirrel-cage rotor (if the letter “K” is missing, it means the electric motor has a wound rotor)
  • N- heat resistance class of electric motor insulation (heating class H - up to 1800C, heating class F - up to 1550C)
  • 280 - Height of the rotation axis (in mm) from the platform on which the electric motor is installed (or from the lower plane of the motor feet)
  • L- designation of the length of the electric motor frame: S-small (small), M-middle (medium), L-long (long)
  • 10 - number of poles (6, 8, 10, 6/12, 6/16, 6/20, 4/24)
  • U1- type of climatic modification (GOST 15150) (U1, UHL1, T1)

terms of Use

Values ​​of climatic factors external environment For normal use crane electric motors are regulated by GOST 15150 and GOST 15543.1 for various types climatic version:

  • the upper value of the operating temperature of the ambient air is not higher than 50°C, the lower value of the operating temperature: for U1 - not lower than 45°C; for UHL1 - not lower than 60°C; for T1 - not lower than 1°C.
  • relative humidity environment: for climatic versions U1, UHL1 - 80% at 15°C; for climatic versions T1, O1 - 80% at 27°C.

Crane electric motors are designed for operation in the following conditions:

  • altitude above sea level - no higher than 1000 m.
  • environment non-explosive, does not contain current-carrying dust, aggressive gases and vapors in concentrations that destroy metals and insulation.
  • dust content value - up to 100 mg/m3.

General information

Three-phase crane motors alternating current And direct current(parallel or series excitation) operate mainly in intermittent mode in a wide range of rotation speed control. Moreover, their work is associated with large frequent starts, overloads, braking, and reverses. In addition, crane electric motors operate in conditions of increased vibration and shaking, and in some cases may be subject to harmful effects high temperature, gases, vapors. As a result, in terms of their characteristics and technical and economic indicators, crane electric motors differ significantly from conventional electric motors.

Features of crane engines

The main features of crane electric motors include the following points that distinguish them from general industrial versions:

  • are produced, as a rule, in a closed protected design;
  • the insulation used in the design has classes F and H in terms of resistance to heat;
  • have a minimal moment of inertia and low rotation speeds, which can significantly reduce losses electrical energy at the time of transition processes;
  • have a small magnetic flux, which provides a high torque overload capacity;
  • have excellent indicators of short-term overload torque (for DC motors - from 2.15 to 5.0, and for AC motors - from 2.5 to 3.5).

Main types of crane engines

The most widely used to drive a crane mechanism is a three-phase asynchronous motor with a wound rotor, which allows you to regulate the speed and obtain smooth start at low load values ​​on the rotor shaft. Electric motors with a wound rotor installed on crane installations, can work in any mode, including the heaviest. Such units allow the possibility of regulating the starting torque and speed within specified limits.

Another type of crane motor can be considered asynchronous electric motors with a squirrel-cage rotor, which are used much less frequently, since they have a slightly reduced starting torque and higher starting current values. True, the mass of these engines is somewhat less than that of models with a wound rotor, at a lower cost with the same power. The use of such electric motors in difficult conditions is limited due to the small permissible number of switchings and the complexity of the circuits that regulate the rotation speed.

A crane electric motor is used to lift loads to different heights. Its peculiarity is that it is designed to operate in frequent starts. An ordinary engine, even a fairly powerful one, under such conditions overheats greatly and fails.

The crane's electric motor operates at 380 volts, although there are options for other power supply values. As a rule, these are three-phase asynchronous devices with a wound rotor, regulated using resistances. In some models of taps, instead of resistors, thyristor regulators with horizontal control of the opening angle are installed. Such schemes allow for a smooth start, which eliminates jerks and jolts, and also makes working with the crane more comfortable and safe. DC motors can be used for the same purposes.

  • Phase devices
    • Reduced speed
    • Braking
  • Other engine types

Phase devices

In overhead cranes, as a rule, there are asynchronous motors with a wound rotor, for example, MTN. Such motors provide a smooth start and also allow you to regulate the speed, despite the significant load on the shaft. They are installed on medium, heavy and very heavy duty equipment. The advantage of MTN over DC motors is their lower price and ease of maintenance. If you compare the masses of these engines on overhead cranes, you will see that phase engines are several times lighter.

If the total costs of operating short-circuited asynchronous machines taken equal to one, then for phase devices they will be equal to five, and for DC motors - ten. This explains why the vast majority of motors on cranes are three-phase.

For domestic industry, electric motors are produced with different heat resistance of insulation, indicated by a letter in the device model: MTF - 155 ○ C, MTN - 180 ○ C.

Electric machines for bridges, as well as other cranes, the MTN and MTKN series are produced with a rotation speed of 600, 750 and 1 thousand rpm. at 50 Hz, and for a network frequency of 60 Hz - 720, 900 and 1200 rpm. This series is characterized by high overload capacity, increased starting torque with low current and fast acceleration.

MTN motors have increased power due to improved characteristics of insulating materials, compared to previous models of similar electrical machines.


The phase rotor has three windings arranged with a shift of 120 degrees. The winding is connected only by a star, and its ends are brought out to slip rings made of either brass or steel and well insulated from each other, as well as from the shaft on which they are mounted. Using a brush mechanism, the rotor windings are connected to starting or control equipment.

Starting equipment can be powerful resistors, several starters that gradually short-circuit the rotor, and a time relay.

To save on electricity bills, our readers recommend the Electricity Saving Box. Monthly payments will be 30-50% less than they were before using the saver. It removes the reactive component from the network, resulting in a reduction in load and, as a consequence, current consumption. Electrical appliances consume less electricity and costs are reduced.

Similar schemes work successfully on overhead cranes. After starting, the MTN engine turns on full meaning resistance in the rotor circuit. After a certain time set on the time relay, when the starting current drops to the nominal value, the first contactor is turned on, which, as it were, “throws out” part of the resistance and the engine receives additional torque, accelerating to the next value. In each individual case, the number of resistors and surge starters may be different.

When the last starter is turned on, the MTN reaches its full speed and operates as an asynchronous machine with a squirrel-cage rotor. Crane electric motors with a wound rotor can be used for both short-term and permanent operation.

Reduced speed

Modern overhead cranes use electronic circuit, allowing you to get a reduced, or “creeping” speed. This is extremely necessary in cases of loading dangerous or oversized cargo, and also in cases where very precise loading is needed.

For this purpose, thyristors or triacs are used. Receiving voltage from the rotor phase rings, the circuit sets the opening angle of the thyristor according to the specified value. As a result, the driver can adjust the desired speed, if such adjustment is displayed in his cab, or turn on the set value.


Braking

For engine braking on bridges, and not only on cranes, they are successfully used. dynamic mode: after the power is turned off, a constant voltage having a stationary magnetic field is briefly supplied to the stator winding. This method allows you to increase the accuracy of stopping the mechanism.


This voltage is supplied either through a quenching resistor or using a step-down circuit. After stopping the engine, it must be de-energized.

Other engine types


DC electric motors are widely used in the crane industry. They are manufactured with a power range from 2.5 to 185 kW. Degrees of protection: IP20 – protected assembly, independent airflow; IP23 – completely closed assembly.

If the excitation is either mixed or parallel, then these windings do not need to be de-energized. This is due technical characteristics given electric machine, designed for long-term operating conditions.

If the excitation of the device is sequential, then the windings are assembled from two groups. At 220 V they are assembled and connected to each other in series, if 110 V - in parallel, and if the engine is powered by 440 V - in series-parallel with an additional resistor.


The rotation speed is regulated in two ways: by weakening the excitation voltage or increasing it at the armature.

DC electric motors with parallel excitation and a stabilizing winding, according to their characteristics, allow rotation acceleration to be twice the nominal value by reducing the excitation voltage. If this is a low-speed engine type, then you can increase the speed by 2.5 times.

However, it is worth remembering this limitation: for 220 V devices at increased speed, the torque should be no higher than 0.8 Mn, and for 440 V motors - no higher than 0.64 Mn.

Electric motors for cranes have their own characteristics that must be taken into account when installing them on the appropriate mechanisms.

TOwound electric motors of three-phase alternating current (asynchronous) and direct current (series or parallel excitation) operate, as a rule, in intermittent mode with wide control of the rotation speed, and their operation is accompanied by significant overloads, frequent starts, reverses and braking.

In addition, electric motors of crane mechanisms operate under conditions of increased shaking and vibration. In a number of metallurgical shops, in addition to all this, they are exposed to high temperatures (up to 60-70 o C), vapors and gases.

In this regard, in terms of their technical and economic indicators and characteristics, crane electric motors differ significantly from electric motors of general industrial design.

Main features of crane electric motors:

    execution is usually closed,

    insulating materials have heat resistance classes F and H,

    The moment of inertia of the rotor is as minimal as possible, and the nominal rotation speeds are relatively small - to reduce energy losses during transition processes,

    the magnetic flux is relatively large - to ensure high torque overload capacity,

    the value of short-term torque overload for crane DC electric motors in hourly mode is 2.15 - 5.0, and for AC electric motors - 2.3 - 3.5,

    ratio of maximum permissible operating frequency rotation to the nominal value is 3.5 - 4.9 for DC electric motors, 2.5 for AC electric motors,

    for AC crane electric motors, the rated mode with PV is taken as the 80 min (hourly) mode.

the use of new materials - cold-rolled electrical steel, insulating materials based on synthetic films and phynylon paper, enameled wires of increased resistance, etc.

expansion of the power scale of eight-pole electric motors to 200 kW,

technically possible unification of electric motors of this series with electric motors of the 4A series,

The designation of electric motors of the 4MT series includes the height of the rotation axis (mm) in the same way as for electric motors of the 4A series.

Crane-metallurgical DC electric motors are manufactured in the power range from 2.5 to 185 kW at rotation speeds and are manufactured with insulation of heat resistance class H.

Degree of protection of electric motors: I P20 - for a protected version with independent ventilation, I P23 - for a closed version. Beds D series electric motors up to version 808 - one-piece, and starting from version 810 - detachable.

The excitation windings (with parallel and mixed excitation) are designed for continuous operation, i.e. they may not be switched off while the electric motor is stopped. The parallel excitation windings consist of two groups, which, when switched on at a voltage of 220 V, are connected in series: at 110 V - in parallel, at 440 V - in series with additional resistors connected in series,

The motors are designed to regulate the rotation speed by weakening the magnetic flux or increasing the armature voltage.

Motors with parallel excitation and with a stabilizing winding allow an increase in rotation speed relative to the nominal by a factor of two (low-speed motors with a stabilizing winding - by 2.5 times) by reducing the excitation current.

With such an increased rotational speed, the maximum torque should not exceed 0.8 Mn - for electric motors with a voltage of 220 V and 0.64 Mn - for electric motors with a voltage of 440 V.

Electric motors for cranes