1. Voltage unbalance in supply side (1% volts could easily be 10% current).
2. Physical differences between individual stator coil shapes and connections causing small (but noticeable) resistance changes.
3. Unsymmetrical magnetic circuit - not as big a deal in the smaller "ring" lamination designs, unless highly saturated.
4. Lightly loaded machines will exhibit far higher unbalance than those loaded closer to the full nameplate rating (mostly due to the magnetizing current requirements and associated core/stray loss).
2. Physical differences between individual stator coil shapes and connections causing small (but noticeable) resistance changes.
3. Unsymmetrical magnetic circuit - not as big a deal in the smaller "ring" lamination designs, unless highly saturated.
4. Lightly loaded machines will exhibit far higher unbalance than those loaded closer to the full nameplate rating (mostly due to the magnetizing current requirements and associated core/stray loss).
For 3 phase motor designs, there is hardly any slot combination that will yield a perfectly smooth torque-speed curve. Keeping the following rules in mind will (mostly) avoid the combinations that tend to amplify magnetic noise, harmonics, and parasitic torques.
My experience with the types of motors in electric vehicle is the following. There are three choices for motors in EVs, permanent magnet PM, integral permanent magnet IPM, and induction motor IM. They each have their pros and cons. A PM has the highest power density.
When operating an AC machine on a variable frequency drive, the most common approach is to mimic the DC curves. This is done by using a constant volt/hertz ratio until a "base" speed is achieved at rated terminal volts. Typically, this occurs at line frequency. For "extended" or "field weakening" operation, the terminal voltage is held constant and the applied frequency allowed to increase to obtain the desired speed.
Soft starter allows the output voltage decreases gradually to achieve soft stop, in order to protect the equipment. Such as the impact of the water pump, when the pump stops suddenly, the water flow inertia in the pipe will raise the pipe and valves pressure suddenly and cause pipeline damaged. Soft stop to extend parking time will solve such the impact.
We also recommend looking for faults conducive to stator failures. For example, if you have a high restive imbalance on the circuit this can increase heat inside the motor. The increased heat further stresses the insulation system and can lead to bigger insulation or stator failures. If we could have found the small problem, ie. resistance imbalance, then we could have prevented the stator fault.
The voltage transient which occurs whenever there is a sudden change in current in an inductive device. Inductors resist a sudden current change.
V=L di/dt
In electric motors this occurs at start up when the contactors close and shut down when the contactors open. Soft starts reduce the start up transient, but not the shutdown transient.
This also occurs with variable frequency drives which switch the current rapidly and repeatedly.
V=L di/dt
In electric motors this occurs at start up when the contactors close and shut down when the contactors open. Soft starts reduce the start up transient, but not the shutdown transient.
This also occurs with variable frequency drives which switch the current rapidly and repeatedly.
Soft Starter reduces electric motor starting current to 2-4 times during motor start up, reduces the impact to power grid during motor start up, avoid the motor being burned out, and provide protection in motors running process.
Variable Frequency Drive allows the electric motor smooth start up, control startup current growing from zero to motor rated current...
Variable Frequency Drive allows the electric motor smooth start up, control startup current growing from zero to motor rated current...
In speaking with many engineers over several decades, a large manufacture of large electric motors, have decided once a rotor is identified as the problem, rebarring, or any single repair is usually unsuccessful, and their procedure is to scrap the rotor completely.
PG is short for Pulse Generator, generally it is used for measuring rotational speed. The most common PG card is optical encoder.
PG card is a part of vector variable frequency drive, to convert the encoder different form signals to suitable for the controller, like: electrical level conversion, analog digital conversion, optical isolation, etc.
PG card is a part of vector variable frequency drive, to convert the encoder different form signals to suitable for the controller, like: electrical level conversion, analog digital conversion, optical isolation, etc.
The condition of the rotor bars will determine how much torque your motors will deliver. As a person who has been in the electric motor repair business all my life it is something I constantly check. When a motor is developing open rotor bars it will become noisy on start up. Noisier with each bar that becomes open. It can sound like a cement mixer or as if there is no lubrication in the bearings.
Soft starters and variable frequency drives are two different purpose products. VFD is for AC motor speed control, it's not only change the output voltage but also change the frequency; Soft starter is a regulator actually for motor starting, just changing the output voltage. Variable frequency drive has all the features of soft starters, but the price is much more expensive than the soft starter and the structure is much more complex.
Gozuk Blog: all about electric motor control & drives industries development in energy saving applications.Featured
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A frequency inverter controls AC motor speed. The frequency inverter converts the fixed supply frequency (60 Hz) to a ...
Motor starter (also known as soft starter, motor soft starter) is a electronic device integrates soft start, soft stop, ...
Soft starter allows the output voltage decreases gradually to achieve soft stop, in order to protect the equipment. Such as the ...
Soft Starter reduces electric motor starting current to 2-4 times during motor start up, reduces the impact to power grid during ...
A frequency inverter controls AC motor speed. The frequency inverter converts the fixed supply frequency (60 Hz) to a ...
Motor starter (also known as soft starter, motor soft starter) is a electronic device integrates soft start, soft stop, ...
Soft starter allows the output voltage decreases gradually to achieve soft stop, in order to protect the equipment. Such as the ...
Soft Starter reduces electric motor starting current to 2-4 times during motor start up, reduces the impact to power grid during ...
In Discussion
ATR data sheet
What kind of fluctuations are present at the line voltages (3p 4wire)
Tap-off 132kV from tower step-down to 22kV
What is electromagnetic interference in power electronic circuits?
Centrifugal pump in series with a rotating positive displacement pump
High Current Inductors
90V to 265Vac Input with PFC & Output of 60V, 3000W
How we can interface a machine with a computer
What kind of fluctuations are present at the line voltages (3p 4wire)
Tap-off 132kV from tower step-down to 22kV
What is electromagnetic interference in power electronic circuits?
Centrifugal pump in series with a rotating positive displacement pump
High Current Inductors
90V to 265Vac Input with PFC & Output of 60V, 3000W
How we can interface a machine with a computer
