Iacdrive|Automation Solution

Motor die-cast rotor non-grain-oriented VS grain-oriented

If the material is non-grain-oriented, the path of least resistance for the magnetic flux varies widely from point to point across the sheet: in one place it may go left-to-right across the sheet surface, in another top-to-bottom, and in still another through the sheet. Other points may be anywhere and everywhere in between.

If the material is grain-oriented, the material is aligned such that there is a significant reduction in the energy requirement for passing flux in one direction relative to any other.

Most machines work best with a uniform flux distribution at all points of the airgap surface: this is achieved by stacking both stator and rotor using non-grain-oriented laminations in any arrangement. However, for a grain-oriented material, each lamination has to be rotated by some angle with respect to the one above and below it in the stack (think of it like a spiral staircase).

Regardless of how the winding is made for the rotor (form wound, bar and ring, or die-cast), it is the STACKING process for the core steel that affects grain orientation.

As to skewing BOTH stator and rotor … why? It is a more costly and complex manufacturing process to produce a skewed core vs an unskewed one, regardless whether the skew is in the rotor or stator. Once the skew is begun, there is no real cost difference between a full slot skew and a fractional slot skew.

If you really want to skew both, though – opt for a half-slot skew in one direction in the rotor, and a half-slot skew in the opposite direction for the stator. Note that this means there is only ONE way to assemble rotor and stator together – with the skews opposing. (With the full slot skew on either rotor or stator and an unskewed opposite piece, the rotor can be inserted from either end of the stator with the same effect.)

Variable frequency drive applications

Due to variable frequency drive maintenance and repair experiences.

Die-cast rotor design

The method of creating a die-cast rotor is as follows:

1. An assembly of steel laminations (which may or may not be grain-oriented) containing the openings for both rotor bars and ventilation (as required) is made and clamped together to form a cylindrical iron core.
2. The assembly is inserted into a mold, which has space both above and below the core for the end (shorting) ring assembly.
3. The molten conductor material (aluminum or copper, usually) is injected into the mold and allowed to flow through the bar openings. It also fills the end ring spaces.
4. The entire assembly is allowed to cool so that the conductor solidifies.
5. The “cast” core is then shrunk onto a steel shaft.

Now we have a “cast” rotor assembly, ready for bearings and mounting into machine.

Frequency inverter failure analysis

Transistor frequency inverter has the following disadvantages: easy trip, difficult re-start, poor overload capacity. As the rapid development of IGBT and CPU, the inverter drive integrates perfect self-diagnosis and fault prevention features, improve the reliability greatly.

Vector control frequency inverter has “automatic torque compensation function” to overcome “starting torque inadequate” etc. This function is the inverter uses a high-speed microcomputer to calculate the torque required at current time, to modify and compensate the output voltage quickly to offset the frequency inverter output torque changed by external conditions.

In addition, because as the inverter software development more and more perfect, we can pre-set various failures parameters in the frequency inverter, to ensure continuous running after failure resolved. For example, re-start motor in free parking process; automatic reset internal failures and maintain continuous operation; adjust running curve if load torque is too high to detect the mechanical system abnormal.

Electric motor rotor and stator

When building a traditional electric machine (motor or generator), the idea is to distribute the flux very evenly over both the rotor and stator surfaces where they contact the air gap. This means using either grain-oriented steels and rotating each lamination slightly from the previous one to provide a relatively even flux path, or using a non-grain-oriented steel and having the flux distribute on its own.

Grain-oriented steels are good for lowering magnetizing flux – provided the grain in each lamination is aligned in the same direction. This can also help with reducing stray loss and eddy loss (flux that travels parallel to the shaft and does no useful “work”).

Most electrical steels used in stator and rotor construction also have an insulating coating applied; some of these are organic materials and some are inorganic (solvent-based) materials. The choice is typically made based on a combination of temperature gradient and local environmental laws. The inorganic (solvent) materials can generally withstand higher temperatures but are far less eco-friendly in the manufacture of the coating material or in the curing of the coating after it is applied.

Since most coatings are applied after the rolling-to-thickness process, these are usually cold-rolled steels. The use of cold- vs hot-rolled material can also be based on tooth / slot geometry: for very narrow teeth that require “post processing” for a coating, hot rolled is often used because the material will retain its geometry better through the temperatures used to cure the coating.

Skewing is the relationship between a rotor “turn” and a stator “turn”. Each manufacturer is different; and different machines (synchronous, induction, Permanent magnet, direct current) approach it differently. For example – it is usually easier to skew the stator laminations of an AC machine, because the insertion of the coils is easier. For a DC machine, skewing of the rotor is preferred for the same reason. The amount of skew is typically one slot pitch … which means that one end of the machine has the slot centerline aligned with the opposite end’s tooth centerline.

Grain orientation only applies to the lamination steels … not the conductor materials.

Energy efficient bearing is really a misnomer. However, they can be thought of as those that are sized to have relatively low friction coefficients and therefore low thermal losses (so that you don’t have to use extra energy to cool the lubricant). In the bigger picture, they would also use a lubricant that is less energy-intensive to produce and / or require less replacement.

Avoid variable frequency drive damaged in lightning

Sometimes

Energy Efficient Motor VS Standard motor

This is a very simplified comparison for a very complex issue. Every motor manufacturer is somewhat different in their approach, and there are literally thousands of design details in each machine that can be accommodated as the designer balances efficiency VS performance VS cost VS reliability VS safety VS manufacturability.

To generalize a bit, take a look at the following list. Not everything is there (not by a long shot!) but there should be enough to give you a reasonable overview. Note that some items are “design” related, while others are “operation” related.

1. Use a lower loss material for both stator and rotor laminations.
2. Use a larger copper cross-section for the same power rating.
3. Skew rotor winding with respect to stator winding.
4. Use more magnetic material (diameter, length, or both) to reduce flux densities.
5. Effectively size the machine for a somewhat higher rating than nameplate (because the typical peak of the efficiency curve occurs somewhere between 70 and 85 percent “rated” load).
6. Operate the machine at reduced temperatures and/or increase coolant flow.
7. Limit input frequency and/or voltage variation to tighter tolerance (note that this is a specification approach, not a manufacturing approach).
8. Better bearings / lubrication to reduce friction loss.
9. More care taken with internal geometry – i.e. closed slots, large air gaps, generous tooth dimensions, smooth surfaces, etc – to reduce windage.

How to learn PLC technology languages

The PLC languages themselves are fairly similar between different manufacturers. You basically have ladder logic (which looks like a relay contact map), function blocks (which are more akin to an electronic circuit overview) and structured language (of which there are several variants. Most look a lot like high-level programming languages). You might encounter some functions having different names or in-/outputs between manufacturers but most of them look much the same. They have the same functionality although complex programming is easier in structured code. If you have worked with high-level programming, you might want to take a look at structured languages first as these will likely feel familiar.

As for ease-of-use, I usually recommend the larger manufacturers; not because these have the best, cheapest or easiest software but because they have very substantial and comprehensive online support which, for a beginner, is more helpful than a cheap program. The big companies such as Siemens, Schneider, ABB and Rockwell all have very comprehensive online help, programming examples and guides as well as manuals available. Most also have “starter-kits” of their software and hardware available although these of course require some form of budget.

Soft starter MCC control cabinet

MCC is shorted for Motor Control Center. Soft starter MCC control cabinet consists of the following components: (1) input circuit breaker, (2) Soft starter (including electronic control circuit and three phase thyristor), (3) soft starter bypass contactor, (4) secondary-side control circuit (for manual start, remote start, soft start and direct start functions selection and operation), and voltage, current display, fault, running and working status indicators.

We can achieve various complex functions with combinations of soft starter MCC control cabinet. For example: add logic controller to two control cabinets to form a “alternative solution” for building’s fire protection system, sprinkler pumps etc. Couple with PLC (programmable logic controller), we can achieve automatic detection (eg half a month) and shutdown of the fire pump system; couple with corresponding logic controller to make the pump running at low speed and low pressure in setting time when we maintenance the whole system working status. Combine logic controller with several motors for residential pump system and other dedicated systems, active each motor according to actual requirements and also can reduce motor gradually to achieve optimum operation efficiency. Also can achieve multiple motors running by turns according to customer requirements, to make all motors operating life in the same.

Soft starter protection features

1) Overload protection: the soft starter has current control loop to track and detect of the changes of the electric motor current. Achieve overload protection by increasing overload current settings and inverse time control mode, to cut down the thyristor and send alarm signals when motor is overload.
2) Phase loss protection: soft starter detects changes in the three-phase line current all the time, to make phase loss protection response once the current off.
3) Overheating protection: the soft starter detects the thyristors internal radiator’s temperature by its thermal relay, automatic cut down and send alarm signal once the radiator’s temperature exceeds the allowable value.
4) Other features: achieve lots of mixed protection functions by combination of the electronic circuits.