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It is difficult to make this measurement but not impossible. One way to do it is to make a Wye resistive network and then connect a resistor from the common neutral point to chassis ground. You would then measure the scaled common mode voltage from the neutral to ground.
More importantly, the result of common mode current is the common mode current flowing from the inverter into the motor. This is a function of the motor internal capacitance to ground. It is easy to measure the common mode current. You simply find a rogowski coil that has sufficient high frequency bandwidth or (better yet) use a current transformer. Measure the frequency inverter common mode current by routing all three output phase conductors through the sensor. This will give you an indication of the common mode voltage (and is what you care about anyway).
More importantly, the result of common mode current is the common mode current flowing from the inverter into the motor. This is a function of the motor internal capacitance to ground. It is easy to measure the common mode current. You simply find a rogowski coil that has sufficient high frequency bandwidth or (better yet) use a current transformer. Measure the frequency inverter common mode current by routing all three output phase conductors through the sensor. This will give you an indication of the common mode voltage (and is what you care about anyway).
Solar Inverters for grid connection and have been developed in order to minimize cost, better performance and extreme simplicity of construction, operation and maintenance. Applications: residential installations, industrial installations, big photovoltaic plants, isolated installations, etc. Multi-megawatt solutions customized to each project and string boxes to maximize the solar PV systems.
Gozuk photovoltaic inverters developed from its experienced designing and manufacturing industrial, robust, reliable, secure and high efficiency power electronics systems. The PV Inverter turns the DC mains coming from a solar PV field into a stabilized AC voltage power output. The central inverter works in grid connected mode, injecting the produced power.
Gozuk photovoltaic inverters developed from its experienced designing and manufacturing industrial, robust, reliable, secure and high efficiency power electronics systems. The PV Inverter turns the DC mains coming from a solar PV field into a stabilized AC voltage power output. The central inverter works in grid connected mode, injecting the produced power.
This configuration, sometimes referred to as a "shoebox on the wall" is the least expensive option of the three major types. It features a basic frequency inverter connected between the line and the load. Speed control is generally operator initiated either through a front panel keypad or speed potentiometer. Functionality and features on this type of frequency inverter are generally limited. It should be noted that an external disconnect is required and that this type of frequency inverter may not be suitable for filter room applications due to the harsh environment and the lack of a secondary enclosure. One major issue with this type of frequency inverter is that being the sole load driving component, a failure of the frequency inverter will bring the entire system down until the frequency inverter is removed from service for repair or replacement.
Tags: inverter, Frequency inverter
Inverter is capable to smoothly starting AC motors (ramp from 0 up to 100% of the load) as well as the energy saving will be achieved, accordingly. Also may I confirmed that frequency inverter also acting as AC Motor starting means among (Star/Delta, Soft Starter, Auto Transformer, Electrolyte, series resistance - wound rotor- etc,). The starting factor of frequency inverter is usually 1 up to 1.2 with respect to the rated load current while for Direct On line about 5-6.
Moreover and as you know the inverter can control the speed of the AC motors in accordance to the formula N=120f/P rpm
where f = the supply frequency and P = number of the Poles.
According to this formula, Motor Speed can be changed either by changing/control the frequency or by changing the number of Poles of the Motor by which step changed in the RPM will be given, while the former gives continuous variable speed as per application demand.
However, as per newly developed power Semi Conductor IGCT based on PWM frequency inverter became the most smart, effective and efficient control device in Industries since is associated also with protective and monitoring means.
Moreover and as you know the inverter can control the speed of the AC motors in accordance to the formula N=120f/P rpm
where f = the supply frequency and P = number of the Poles.
According to this formula, Motor Speed can be changed either by changing/control the frequency or by changing the number of Poles of the Motor by which step changed in the RPM will be given, while the former gives continuous variable speed as per application demand.
However, as per newly developed power Semi Conductor IGCT based on PWM frequency inverter became the most smart, effective and efficient control device in Industries since is associated also with protective and monitoring means.
Noise radiated from a frequency inverter cable is proportional to the amount of varying electric current within it. As cable lengths grow, so does the magnitude of reflected voltage. This transient over voltage, combined with the high amplitudes of current associated with frequency inverters, creates a significant source of radiated noise. By shielding the frequency inverter cable, the noise can be controlled. In the tests presented in this paper, relative shielding effectiveness was observed by noting the magnitude of noise coupled to 10 ft. of parallel unshielded instrumentation cable for each frequency inverter cable type examined. The results of the shielding effectiveness testing are documented in the Figure.
As demonstrated by its trace in that figure, foil shields are simply not robust enough to capture the volume of noise generated by frequency inverters. Unshielded cables connected between a frequency inverter and a motor can radiate noise in excess of 80V to unshielded communication wires/ cables, and in excess of 10V to shielded instrumentation cables. Moreover, the use of unshielded cables in conduits should be limited, as the conduit is an uncontrolled path to ground for the noise it captures. Any equipment in the vicinity of the conduit or conduit hangers may be subject to an injection of this captured, common- mode noise. Therefore, unshielded cables in conduit are also not a recommended method for connecting frequency inverters to motors.
As demonstrated by its trace in that figure, foil shields are simply not robust enough to capture the volume of noise generated by frequency inverters. Unshielded cables connected between a frequency inverter and a motor can radiate noise in excess of 80V to unshielded communication wires/ cables, and in excess of 10V to shielded instrumentation cables. Moreover, the use of unshielded cables in conduits should be limited, as the conduit is an uncontrolled path to ground for the noise it captures. Any equipment in the vicinity of the conduit or conduit hangers may be subject to an injection of this captured, common- mode noise. Therefore, unshielded cables in conduit are also not a recommended method for connecting frequency inverters to motors.
Frequency inverters require an acceptable electrical supply for safe, successful and reliable operation.
Single phase inverters have standardized voltages of 120 and 240 volts. Three phase motors have standardized voltages of 200, 230, 460 and 575 volts.
The nominal supply voltage of the distribution system is normally higher than the inverter nameplate voltage to allow for voltage drops from the distribution transformer to the point of utilization.
Rated frequency is usually 60Hz (hertz or cycles per second) in North America.
Harmonics
Harmonic distortion of voltage and current is produced in electrical systems by non-linear loads such as frequency inverters, welders, rectifiers, Uninterruptible Power Supplies (UPS), arc furnaces etc. Harmonics cause electrical waveform distortion that can propagate through the entire power system and even outside of the plant. The source of harmonic distortion in frequency inverters is the solid-state power switching devices used to generate the varying supply frequencies.
These effects, known as "line harmonic currents", are multiples of the fundamental 60 Hz supply current. For example, a frequency of 180 Hz is called the third harmonic. These currents generate harmonic voltage distortions which often exceed acceptable levels.
For more information, refer to the CEATI Power Quality Energy Efficiency Reference Guide.
Harmonic Components
Harmonic Amplitudes
The odd harmonic amplitudes usually decrease with increasing frequency, so the lowest order harmonics are the most significant. Even numbered harmonics are not normally generated by frequency inverter systems.
Harmonics occur as long as the harmonic generating equipment is in operation and tend to be of a steady magnitude.
Harmonics may be greatly magnified by power factor correction capacitors. The supply system inductance can resonate with capacitors at certain harmonic frequencies developing large currents and voltages, which can damage equipment.
Single phase inverters have standardized voltages of 120 and 240 volts. Three phase motors have standardized voltages of 200, 230, 460 and 575 volts.
The nominal supply voltage of the distribution system is normally higher than the inverter nameplate voltage to allow for voltage drops from the distribution transformer to the point of utilization.
Rated frequency is usually 60Hz (hertz or cycles per second) in North America.
Harmonics
Harmonic distortion of voltage and current is produced in electrical systems by non-linear loads such as frequency inverters, welders, rectifiers, Uninterruptible Power Supplies (UPS), arc furnaces etc. Harmonics cause electrical waveform distortion that can propagate through the entire power system and even outside of the plant. The source of harmonic distortion in frequency inverters is the solid-state power switching devices used to generate the varying supply frequencies.
These effects, known as "line harmonic currents", are multiples of the fundamental 60 Hz supply current. For example, a frequency of 180 Hz is called the third harmonic. These currents generate harmonic voltage distortions which often exceed acceptable levels.
For more information, refer to the CEATI Power Quality Energy Efficiency Reference Guide.
Harmonic Components
Harmonic Amplitudes
The odd harmonic amplitudes usually decrease with increasing frequency, so the lowest order harmonics are the most significant. Even numbered harmonics are not normally generated by frequency inverter systems.
Harmonics occur as long as the harmonic generating equipment is in operation and tend to be of a steady magnitude.
Harmonics may be greatly magnified by power factor correction capacitors. The supply system inductance can resonate with capacitors at certain harmonic frequencies developing large currents and voltages, which can damage equipment.
Tags: inverter, Frequency inverter
Simulation is checking the logical aspects of the developed system / software & modeling is the back-end development of these system/softwares & files/rules/protocols to which are used in design & verification (logical as well as functional), more realistic is the realistic parameters which matches closely with actual run time environment, more will be the accuracy/precision of simulation/validation results (in short the coverage of functionalities, features & combinations of various real time possibilities/scenarios, matters a lot to reduce the failures after manufacturing of system), different models can are developed as libraries to simulate various real time scenarios/possibilities/features & can be used for practicing/training or actual validation of products as well. So, simulation & modeling both are used by developers of technology & simulation is not necessarily used only by developers, may also, be used by technicians, operators, users who works on higher level of abstraction of concerned systems.
Tags: Simulation, Modeling
Energy Savings with inverters
if you have an AC motor-driven application that does not need to be run at full speed, then you can cut down energy costs by controlling the motor with an inverter (frequency inverter, aka variable frequency drive). Inverters allow you to match the speed of the motor-driven equipment to the process requirement. There is no other method of AC motor control that allows you to accomplish this.
Example of an Excellent inverter Candidate
Example of a Decent inverter Candidate
Example of a Poor inverter Candidate
Variable Torque Versus Constant Torque
inverters, and the loads they are applied to, can generally be divided into two groups: constant torque and variable torque. The energy savings potential of variable torque applications is much greater than that of constant torque applications. Variable torque loads include centrifugal pumps and fans, which make up the majority of HVAC applications. Constant torque loads include vibrating conveyors, punch presses, rock crushers, machine tools, and other applications where the drive follows a constant V/Hz ratio.
Why Variable Torque Loads Offer Great Energy Savings
in variable torque applications, the torque required varies with the square of the speed, and the horsepower required varies with the cube of the speed, resulting in a large reduction of horsepower for even a small reduction in speed. The motor will consume only 25% as much energy at 50% speed than it will at 100% speed. This is referred to as the Affinity Laws, which define the relationships between speed, flow, torque, and horsepower. The following diagram illustrates these relationships.
if you have an AC motor-driven application that does not need to be run at full speed, then you can cut down energy costs by controlling the motor with an inverter (frequency inverter, aka variable frequency drive). Inverters allow you to match the speed of the motor-driven equipment to the process requirement. There is no other method of AC motor control that allows you to accomplish this.
Example of an Excellent inverter Candidate
Example of a Decent inverter Candidate
Example of a Poor inverter Candidate
Variable Torque Versus Constant Torque
inverters, and the loads they are applied to, can generally be divided into two groups: constant torque and variable torque. The energy savings potential of variable torque applications is much greater than that of constant torque applications. Variable torque loads include centrifugal pumps and fans, which make up the majority of HVAC applications. Constant torque loads include vibrating conveyors, punch presses, rock crushers, machine tools, and other applications where the drive follows a constant V/Hz ratio.
Why Variable Torque Loads Offer Great Energy Savings
in variable torque applications, the torque required varies with the square of the speed, and the horsepower required varies with the cube of the speed, resulting in a large reduction of horsepower for even a small reduction in speed. The motor will consume only 25% as much energy at 50% speed than it will at 100% speed. This is referred to as the Affinity Laws, which define the relationships between speed, flow, torque, and horsepower. The following diagram illustrates these relationships.
Tags: inverter, Frequency inverter
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 inverter, to convert the encoder different form signals to suitable for the controller, like: electrical level conversion, analog digital conversion, optical isolation, etc.
Vector control inverter is a high-performance inverter which can be comparable with DC converter.
In the vector control, it requires a motor speed feedback to the frequency inverter, this speed feedback is achieve by adding a rotary encoder (PG) to the motor, which means PG card feedback vector control inverter. In order to simplify the system, the feedback can be formed by operation of the inverter output signal, this control is called none PG card feedback vector control inverter, the performance has a slight gap than PG card feedback, but configuration is simple.
PG card is a part of vector inverter, to convert the encoder different form signals to suitable for the controller, like: electrical level conversion, analog digital conversion, optical isolation, etc.
Vector control inverter is a high-performance inverter which can be comparable with DC converter.
In the vector control, it requires a motor speed feedback to the frequency inverter, this speed feedback is achieve by adding a rotary encoder (PG) to the motor, which means PG card feedback vector control inverter. In order to simplify the system, the feedback can be formed by operation of the inverter output signal, this control is called none PG card feedback vector control inverter, the performance has a slight gap than PG card feedback, but configuration is simple.
Some frequency meters use a micro-ammeter movement and an L-C filter so the micro-amp flow changes with frequency and the needle deflects accordingly. Digital frequency meters often count the rising edge of each sine wave in a given time period (milliseconds) and calculate the frequency accordingly. Some frequency meters contain vibrating "reeds" (thin steel fingers) where each reed is tuned to a specific frequency and vibrates when the power system (usually a generator) is operating at that specific frequency. These particular meters are very precise, but are typically only designed to work in a range of normal line frequency +/- about 5Hz.
Most frequency meters are designed to operate at voltages in the range of 110V, so they are normally connected to the power system through a voltage transformer.
Most frequency meters are designed to operate at voltages in the range of 110V, so they are normally connected to the power system through a voltage transformer.
Tags: Frequency meter
Now for the more complex part. There is no such thing as pure DC. When a DC circuit is first switched on there is a so called rise time during which the voltage and current rise to their steady-state. During this rise time (which is not instantaneous) stray inductance and stray capacitance both play a role. Typically the rise time is very short and could quite correctly be described as one half of a very high frequency AC square wave. As the steady state current and voltage are reached there is a very rapid change from the "high frequency" rise and the very low frequency (for all practical purposes zero frequency) steady state. That is the corner of the (nearly) square wave. That corner represents a very fast transition from super high frequency to effectively zero frequency. During that change a rapid scan through "all" frequencies occurs.
The opposite occurs when the DC circuit is switched off.
Keeping in mind that impedance is made up of capacitance inductance and resistance with frequency as a factor it can be argued that there is no such thing as pure resistance. That is in fact quite correct. In a similar way there is no such thing as a pure capacitor. They all have some inductance and they all have some resistance. Even an inductor has some stray capacitance and it is common knowledge that the wire that makes up an inductor (coil) has some resistance. The deviation between the theoretically pure inductor and what in practice has been achieved is referred to as the Q of the inductor. Similar concepts apply to capacitors and resistors.
At the end of the day the only real measure of "resistance" is impedance. The reality is that the effects capacitance and inductance of DC in steady state can safely be ignored hence the term resistance.
The opposite occurs when the DC circuit is switched off.
Keeping in mind that impedance is made up of capacitance inductance and resistance with frequency as a factor it can be argued that there is no such thing as pure resistance. That is in fact quite correct. In a similar way there is no such thing as a pure capacitor. They all have some inductance and they all have some resistance. Even an inductor has some stray capacitance and it is common knowledge that the wire that makes up an inductor (coil) has some resistance. The deviation between the theoretically pure inductor and what in practice has been achieved is referred to as the Q of the inductor. Similar concepts apply to capacitors and resistors.
At the end of the day the only real measure of "resistance" is impedance. The reality is that the effects capacitance and inductance of DC in steady state can safely be ignored hence the term resistance.
Tags: Impedance, Resistance