BDS Maschinen motor, German BDS Maschinen model, BDS Maschinen price

BDS Maschinen motors are named for their armature winding and field winding connected in series. Single-phase series-wound motors are AC/DC universal motors; they can operate on either AC or DC power supplies. The single-phase series-wound motor is widely used. Its advantages include high speed, high starting torque, compact size, light weight, resistance to stalling, and a wide applicable voltage range. Speed control can be achieved simply and easily by voltage regulation.

BDS Maschinen motor speed control

Motor pole-changing speed control achieves speed regulation by altering the stator winding connections to change the number of pole pairs in the stator of a squirrel-cage motor. Variable frequency drive (VFD) speed control changes the frequency of the stator power supply, thereby altering the synchronous speed. The main equipment in a VFD system is the variable frequency drive, which provides variable frequency power. VFDs fall into two categories: AC-DC-AC converters and AC-AC converters; AC-DC-AC drives are predominantly used domestically. Cascade speed control involves inserting an adjustable additional electromotive force (EMF) into the rotor circuit of a wound-rotor motor to change the slip, achieving speed control. Most slip power is absorbed by the inserted additional EMF and then returned to the grid or converted for useful energy via auxiliary devices. Based on how slip power is absorbed and utilized, cascade speed control can be classified as motor cascade, mechanical cascade, or thyristor cascade, with thyristor cascade being the most common. Inserting additional resistance into the rotor circuit of a wound-rotor asynchronous motor increases the slip, causing the motor to run at a lower speed. The greater the inserted resistance, the lower the motor speed. This method features simple equipment and convenient control, but slip power is dissipated as heat in the resistors. It provides stepped speed control with relatively soft mechanical characteristics. Changing the stator voltage of a motor yields different mechanical characteristic curves, resulting in different speeds. Since motor torque is proportional to the square of the voltage, the maximum torque drops significantly, limiting the speed control range and making this method difficult to apply to general squirrel-cage motors. To expand the speed control range, voltage-regulation speed control should employ squirrel-cage motors with high rotor resistance, such as torque motors designed specifically for voltage-regulation speed control, or connect frequency-sensitive resistors in series with wound-rotor motors. To expand the stable operating range, feedback control should be adopted for speed ratios above 2:1 to achieve automatic speed regulation. The main device for voltage-regulation speed control is a power supply capable of varying voltage. Common voltage regulation methods include series-connected saturated reactors, autotransformers, and thyristor voltage regulation, with thyristor voltage regulation being optimal.

BDS Maschinen motor starting

The armature circuit resistance and inductance of a motor are small, while the rotating mass has certain mechanical inertia. Therefore, when the motor is energized, the armature speed and corresponding back EMF are very low during the initial starting phase, resulting in a very high starting current. It can reach 15 to 20 times the rated current. This current causes grid disturbances, mechanical shock to the unit, and sparking at the commutator. Therefore, direct-on-line starting is only suitable for motors with power not exceeding 4 kW (starting current is 6 to 8 times the rated current). To limit starting current, a specially designed variable resistor is often connected in series in the armature circuit; its principle wiring is shown in Figure 1. During the starting process, as the speed increases, each section of the resistor is short-circuited step by step in time, keeping the starting current within an allowable limit. This method is called series-resistance starting. It is very simple, the equipment is lightweight, and it is widely used in various small and medium-sized DC motors. However, due to high energy consumption during starting, it is unsuitable for motors that start frequently or for medium and large DC motors. Nevertheless, for certain special requirements, such as urban trams that start frequently, series-resistance starting is often adopted to simplify equipment, reduce weight, and facilitate operation and maintenance. For larger-capacity DC motors, reduced-voltage starting is typically used. This involves supplying power to the motor armature from a separate adjustable-voltage DC power source. Controlling the supply voltage enables smooth motor starting and also achieves speed control. This method requires more complex power supply equipment.

BDS Maschinen motor armature reaction

The effect of motor armature current interfering with the magnetic flux generated by the field. The state varies depending on the phase difference between armature voltage and armature current. When the power factor is 1, the flux on the leading side along the direction of pole rotation is strengthened, while the flux on the trailing side is weakened. In motor operation, the flux advances ahead of the rotor, pulling the rotor in the acceleration direction. Conversely, in generator operation, the flux lags behind the rotor, pulling the rotor in the deceleration direction. This corresponds to the torque generated by Maxwell stress based on the principle that "contractile forces act on magnetic lines of force." When the power factor is lagging, the flux acts in the direction of increasing flux. When the power factor is leading, its action weakens the flux. In synchronous generators and synchronous motors, the leading/lagging nature of armature current relative to magnetizing/demagnetizing effects is opposite. This relationship can be unified by understanding whether weak or strong excitation and reactive power are produced or absorbed. In weak excitation, where excitation current decreases, the voltage generated by the synchronous machine (no-load induced EMF) is lower than the system voltage (armature voltage), and the synchronous machine absorbs lagging reactive power from the system. Hereafter, lagging reactive power is referred to simply as reactive power. In this case, the armature reaction becomes a magnetizing effect. The load observed from a synchronous generator produces reactive power at a leading power factor (capacitive). From the power source perspective, a synchronous motor absorbs reactive power and presents a lagging load (inductive). In strong excitation, with high excitation current, the voltage generated by the synchronous machine (no-load induced EMF) is higher than the system voltage (armature voltage), and the synchronous machine supplies reactive power to the system. In this case, the armature reaction becomes a demagnetizing effect. The load seen from a synchronous generator absorbs reactive power with a lagging power factor (inductive). In the case of a synchronous motor, reactive power is produced by the load (capacitive) generated from the power source.

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