VOLLMER motor Germany VOLLMER model VOLLMER price

VOLLMER motors are rotating machines containing a brush assembly that convert DC electrical energy into mechanical energy (DC motors) or convert mechanical energy into DC electrical energy (DC generators). Unlike brushless DC motors, the brush assembly is used to introduce or extract DC voltage and current. Brushed DC motors form the basis of all motors; they feature fast starting, timely braking, smooth speed regulation over a wide range, and relatively simple control circuits.

VOLLMER motor mechanical characteristics

Motor electromagnetic torque: The electromagnetic torque of a three-phase asynchronous motor is produced by the interaction between the magnetic flux per pole φm of the rotating magnetic field and the rotor current I2. Since the rotor circuit is inductive, the rotor current I2 lags behind the rotor electromotive force E2. Therefore, the relationship between torque T, magnetic flux φm, and rotor current I2 is T = K TΦI 2 c o s Ψ 2 (1). In equation (1), KT is a constant related to the motor structure, cosΨ 2 is the power factor of the rotor circuit, and the unit of torque T is Newton-meter (N·m). As seen from the above equation, torque T is directly proportional not only to F but also to I 2 cosy 2. From the circuit analysis of the three-phase asynchronous motor, substituting equations (2), (3), and (4) into equation (1) yields another expression for torque. Equation (5) shows that torque T is also proportional to the square of the phase voltage U1 of the stator winding. Therefore, changes in supply voltage significantly affect torque. Additionally, torque T is influenced by the rotor resistance R2. Mechanical characteristic curve: The curve representing the relationship between electromagnetic torque and slip ratio is the n=f(T) curve. Although the slip ratio s of an asynchronous motor reflects the motor speed n, it is not very intuitive and is inconvenient for application. Therefore, mechanical characteristics are typically used to analyze related drive problems. Under constant supply voltage, the relationship between motor speed and electromagnetic torque is called the motor's mechanical characteristic. The asynchronous motor's n = f(T) curve, the T-s curve, is derived through coordinate axis transformation. When s = 0, n=1; when s=1, n=0. Using speed n as the vertical axis and torque T as the horizontal axis, rotating the T-s curve clockwise by 90° yields the mechanical characteristic curve n = f(T). The purpose of studying mechanical characteristics is to analyze motor operating performance. First, three torques are discussed on the mechanical characteristic curve. Rated torque TN: When the motor rotates at constant speed, its output torque must balance the load torque, which is primarily the mechanical load torque T2. It also includes no-load loss torque (primarily mechanical loss torque) T0. Since T0 is very small and can often be ignored: T = T2+ T0 ≈ T2. Thus, the motor's electromagnetic torque T is approximately equal to the output mechanical torque T2 on the motor shaft. Where: P2 is the mechanical power output on the motor shaft, in Watts (W); the unit of torque is Newton-meter (N.m); the unit of speed is revolutions per minute (r/rnin). If power is expressed in kilowatts, commonly used in engineering: If the mechanical power P2 output on the motor shaft is the rated power P2N, then the output mechanical torque T2 of the motor is the rated torque TN. Maximum torque Tmax. It can be seen that maximum torque Tmax is proportional to U12 and independent of rotor resistance R2; sm is related to R2, and the larger R2 is, the larger sm becomes. The ratio of the motor's maximum torque Tmax to its rated torque TN is called the overload coefficient, denoted by λ. That is, λ=Tmax/TN represents the motor's short-term overload capability. Generally, λ for three-phase asynchronous motors is between 1.8 and 2.2, while for special motors used in metallurgy and lifting, λ is between 2.2 and 3. It should be noted that the motor at TN1. The ratio of the motor's starting torque Tst to the rated torque TN, Kst =Tst/TN, indicates the motor's starting capability. Generally, the Kst value for asynchronous motors is between 1. 4 and 2. 2. Motor operation analysis: When the load torque T2 carried by the motor is less than the starting torque Tst, the motor can start with load. From point c to point b, the motor torque increases with rising speed, causing the motor speed to increase rapidly. At point b, the torque reaches its maximum value Tmax. After passing point b, the motor torque decreases as speed rises. However, as long as the electromagnetic torque T is greater than the load torque T2, the motor speed continues to rise until T = T2, at which point the motor speed stabilizes. Therefore, the stable operating point of the motor lies at some point in the b, a interval of the n = f (T) curve. Hence, the ab region is called the stable operating region. The bc region is the unstable operating region. If the load suddenly increases, or the supply voltage suddenly drops such that T2>Tmax, the motor speed drops rapidly, entering the bc segment. The motor's electromagnetic torque decreases with decreasing speed, causing the motor to stop quickly. This phenomenon is called stall. After stalling, the current in the motor immediately rises to several times the rated current. If there are no protective measures to cut off the power supply in time, the motor may be burned out.

VOLLMER motor protection device

Motor differential protection devices are mainly used in large high-voltage motors in power plants, chemical plants, and other locations. If a severe fault causes motor burnout, it will seriously affect normal production and cause significant economic losses. Therefore, comprehensive protection must be provided. Existing integrated motor protection devices mainly target small and medium-sized motors, providing protection functions such as instantaneous current cutoff, thermal overload inverse-time overcurrent, two-stage definite-time negative sequence, zero-sequence current, rotor stall, excessive start time, and frequent starting. However, for extra-large capacity motors above 2000KW, these devices cannot meet the requirements for protection sensitivity and speed during internal faults. Therefore, this device was developed to work with integrated protection devices, providing more reliable and sensitive protection measures for high-voltage motors. This device is designed as a three-phase longitudinal differential protection because the 3KV, 6KV, and 10KV grids where extra-large capacity motors above 2000KW are located may have transformer neutrals grounded via high resistance. Three-phase longitudinal differential protection serves not only as the main protection against phase-to-phase short circuits in the motor stator windings and lead wires but also as the main protection against single-phase ground faults, acting to trip instantaneously.

VOLLMER motor performance

Motor performance comparison: Comparison of servo motor and stepper motor performance. As an open-loop control system, stepper motors are inherently linked to modern digital control technology. In domestic digital control systems, stepper motors are widely used. With the emergence of all-digital AC servo systems, AC servo motors are increasingly applied in digital control systems. To adapt to the trend of digital control, motion control systems mostly use stepper motors or all-digital AC servo motors as actuator motors. Although both are similar in control method (pulse train and direction signals), there are significant differences in performance and application scenarios. A comparison of their performance follows. One, different control precision: The step angle of two-phase hybrid stepper motors is generally 1.8° or 0.9°, and the step angle of five-phase hybrid stepper motors is generally 0.72 ° or 0.36°. Some high-performance stepper motors achieve smaller step angles through microstepping. Two, different low-frequency characteristics: Stepper motors are prone to low-frequency vibration at low speeds. The vibration frequency depends on the load condition and driver performance; it is generally considered to be half the motor's no-load stepping frequency. This low-frequency vibration, determined by the working principle of stepper motors, is very unfavorable for normal machine operation. When stepper motors operate at low speeds, damping techniques should generally be used to overcome low-frequency vibration, such as adding dampers to the motor or using microstepping technology in the driver. AC servo motors operate very smoothly and do not exhibit vibration even at low speeds. AC servo systems have resonance suppression functions that can compensate for insufficient mechanical rigidity. Furthermore, the system internally has frequency analysis capabilities (FFT) to detect mechanical resonance points, facilitating system adjustment.

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