Wald motor Germany Wald model Wald price

Wald motors consist of the motor body and the driver, representing a typical mechatronic product. A brushless motor refers to a motor without brushes and a commutator (or slip rings), also known as a commutator-less motor. When motors were first invented in the nineteenth century, the practical motors produced were of the brushless type, namely AC squirrel-cage asynchronous motors, which were widely used. However, asynchronous motors have many insurmountable defects, resulting in slow development of motor technology. Transistors emerged in the mid-twentieth century, giving rise to DC brushless motors that use transistor commutation circuits to replace brushes and commutators. This new type of brushless motor is called an electronically commutated DC motor, which overcomes the defects of the first generation of brushless motors.

Wald motor mechanical characteristics

The characteristic where the motor speed n changes with torque T [n=f(T)] is called the mechanical characteristic. It is an important basis for selecting electric motors. Various types of motors are suitable for different applications due to their specific mechanical characteristics. From the perspective of the DC motor armature circuit, the supply voltage U must balance the motor's back EMF Ed and the voltage drop across the armature circuit resistance Rd caused by the armature current Id, i.e., U=Ed+IdRd. The back EMF is related to the motor speed n and magnetic flux φ, and the armature current is related to the mechanical torque M and magnetic flux φ, i.e., for the z4 series DC motor, Ed=Cφn, M=CφId, where C is a constant. Thus, n0 is the no-load speed, and k is Rа/C2. The above represents the ideal relationship without considering factors such as iron core saturation, but it is also instructive for the analysis of actual DC motors. As seen above, DC motors have 3 speed control methods: adjusting the excitation current, adjusting the armature terminal voltage, and adjusting the resistance inserted in series into the armature circuit. The method of adjusting the series resistance in the armature circuit is relatively simple but involves high energy consumption; furthermore, under light loads, the voltage drop across the series resistance is small due to the low load current, resulting in insensitive speed regulation. Adjusting the armature terminal voltage and appropriately adjusting the excitation current allows for smooth speed control of the DC motor over a wide range. Increasing the terminal voltage increases the speed, while increasing the excitation current decreases the speed; proper coordination of the two allows the motor to operate at different speeds. During speed control, attention should be paid to the fact that commutation conditions deteriorate at high speeds, and cooling conditions worsen at low speeds, thereby limiting the motor's power. Series-wound DC motors, due to their mechanical characteristics (Fig. 2) approaching constant power characteristics and having high torque at low speeds, are widely used for traction in electric vehicles. In trams, two or more compound-wound DC motors, having both series and shunt windings, are commonly used for joint drive. By using series-parallel reconnection methods, the motor terminal voltage can be changed by multiples (the motor terminal voltage in series is only half of that in parallel), thereby economically achieving a wider range of speed control and reducing energy consumption during startup.

Wald motor fault handling

Motor winding ground fault. 1. Fault symptoms: the housing becomes live, control circuits become uncontrollable, and windings short-circuit and overheat, causing the motor to fail to operate normally. 2. Causes: winding dampness reduces insulation resistance; long-term overload operation of the motor; corrosion by harmful gases; intrusion of metal foreign objects into the windings damaging insulation; insulation damage and contact with the iron core during stator winding rewinding; winding ends contacting the end cover or frame; insulation burnout caused by stator-rotor friction; lead wire insulation damage causing contact with the housing; insulation breakdown due to overvoltage (such as lightning strikes). 3. Inspection methods: (1) Visual inspection. Visually inspect the insulation at the winding ends and within the slots for damage and scorch marks; if present, these indicate the ground point. (2) Multimeter inspection. Use the low-resistance range of a multimeter for inspection; if the reading is very low, it indicates a ground fault. (3) Megohmmeter method. Select different megohmmeters according to the voltage class to measure the insulation resistance of each winding group. If the reading is zero, it indicates that the winding is grounded. However, for motor insulation dampness or breakdown due to accidents, judgment must be based on experience. Generally speaking, if the pointer fluctuates unstably at "0", it can be considered to have a certain resistance value. (4) Test lamp method. If the test lamp lights up, it indicates a winding ground fault. If sparks or smoke are observed at a specific location, that location is the ground fault point. If the lamp glows dimly, there is an insulation breakdown to ground. If the lamp does not light up but sparks appear when the test probe is grounded, it indicates that the winding has not broken down but is severely damp. Alternatively, lightly tap the edge of the housing spigot with a hard piece of wood; if the lamp flickers (on and off) at a certain point, indicating intermittent current flow, that point is the ground location. (5) Current burn-out method. Use a variable transformer. After connecting to the power supply, the ground point will heat up quickly, and the spot where the insulation smokes is the ground point. Special care must be taken: for small motors, the current must not exceed twice the rated current, and the duration must not exceed half a minute; for large motors, use 20%-50% of the rated current or gradually increase the current until smoke just appears at the ground point, then immediately cut off the power. (6) Group elimination method. For ground faults located inside the iron core where burning is severe and the burnt copper wire is fused with the iron core, the method involves dividing the grounded phase winding into two halves, and so on, to finally locate the ground point. 4. Remedial methods: (1) If the ground fault is caused by winding dampness, dry the winding first. When it cools to approximately 60–70 °C, apply insulating varnish and dry again. (2) If the insulation at the winding ends is damaged, re-insulate the ground point, apply varnish, and dry again. (3) If the ground point is within the slots, the winding should be rewound or partial winding components replaced. Finally, measure with different megohmmeters to ensure technical requirements are met.

Wald motor working principle

When three-phase currents are fed into the three-phase symmetric windings of the permanent magnet synchronous motor stator, the magnetomotive forces generated by the currents synthesize into a rotating magnetomotive force with a constant amplitude. Since its amplitude remains constant, the trajectory of this rotating magnetomotive force forms a circle, called a circular rotating magnetomotive force. Its magnitude is exactly 1.5 times the maximum amplitude of the single-phase magnetomotive force, where F is the circular rotating magnetomotive force, (T・m); Fφl is the maximum amplitude of the single-phase magnetomotive force, (T・m); k is the fundamental winding factor; p is the number of pole pairs of the motor; N is the number of series turns per coil; I is the RMS value of the current flowing through the coil. Since the speed of the permanent magnet synchronous motor is always the synchronous speed, the rotor main magnetic field and the rotating magnetic field generated by the stator circular rotating magnetomotive force remain relatively stationary. The interaction between the two magnetic fields forms a synthetic magnetic field in the air gap between the stator and rotor, which interacts with the rotor main magnetic field to produce an electromagnetic torque Te that drives or hinders motor rotation, where Te is the electromagnetic torque, (N・m); is the power angle, rad; BR is the rotor main magnetic field, T; Bnet is the air gap synthetic magnetic field, T. Due to the different positional relationships between the air gap synthetic magnetic field and the rotor main magnetic field, the permanent magnet synchronous motor can operate in either motor mode or generator mode. The three operating states of the permanent magnet synchronous motor are shown in Fig. 3. When the air gap synthetic magnetic field lags behind the rotor main magnetic field, the generated electromagnetic torque is opposite to the direction of rotor rotation, and the motor is in generating state; conversely, when the air gap synthetic magnetic field leads the rotor main magnetic field, the generated electromagnetic torque is in the same direction as the rotor rotation, and the motor is in motoring state. The angle between the rotor main magnetic field and the air gap synthetic magnetic field is called the power angle. The permanent magnet synchronous motor consists of two key components: a multi-pole permanent magnet rotor and a stator with appropriately designed windings. During operation, the rotating multi-pole permanent magnet rotor creates a time-varying magnetic flux in the air gap between the rotor and stator. This flux generates an AC voltage at the terminals of the stator windings, forming the basis for power generation. The permanent magnet synchronous motor discussed here uses a ring-shaped permanent magnet mounted on a ferromagnetic core. Internal permanent magnet synchronous motors are not considered here. Because embedding magnets into a plated ferromagnetic core is very difficult, by using magnets of appropriate thickness (500μm) and high-performance magnetic materials in the rotor and stator cores, the air gap can be made very large (300~500μm) without significant performance loss. This allows the stator windings to occupy a certain space in the air gap, greatly simplifying the manufacturing of permanent magnet synchronous motors.

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