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Frequency inverter manufacturers
Frequency converter Q&A
Frequency converter, also called variable frequency drive, typically controls a motor's velocity or torque output.
Most frequency inverters today use pulse width modulation or PWM to create a variable output voltage, current, and frequency. Here, a diode bridge rectifier takes alternating current (ac) power from a power source and provides an intermediate direct current (dc) circuit voltage. In the intermediate dc circuit, the dc voltage travels through a low-pass filter. Then, six high-speed electronic switches in the frequency converter's inverter are controlled to create short pulses with the height of the dc bus voltage and of various widths.
By varying the pulse width, converters create an output waveform with an average that is a sinusoidal voltage and current waveform for which frequency can be varied. It is this variable output that is used to control motor speed, torque, or position.
In the intermediate dc circuit, the dc voltage goes through a low-pass filter.
PWM is used in modern converters because it is efficient. The output switches are either on or off, and don't operate in any intermediate states that can increase power dissipation and energy losses.
Motors driven by frequency converters are sometimes fitted with position feedback devices. In these situations, feedback devices improve motor accuracy, dynamic response, and torque production at low speeds.
How do frequency converters differ from servo drives?
Frequency converters typically control velocity or torque. In contrast, servo drives are often used to control motor position — and almost always use a position feedback device on the motor.
PWM output switches are either on or off, a more efficient design than including intermediate states. By varying the width of the pulses, a converter creates an output waveform for which the average is a sinusoidal voltage and current waveform — the frequency of which can be varied. It is this variable output that is used to control motor speed, torque, or position.
That said, recent frequency converter technology advances are increasingly tailored to specific applications — and don't require changes to entire control systems when added. In addition, the traditional assumptions that frequency converters and induction motors only control speed and servo drives and permanent magnet (PM) motors only control position are being challenged. Why?
First, there's more demand for higher motor efficiency in some frequency converter applications — so frequency converters increasingly control PM motors. Second, the better performance of newer frequency converters is rivaling that of servo drives. Finally. the emergence of Ethernet-based networks improves all types of control, including motion and drive control.
Frequency converters and servo drives share some characteristics: A motor connected to either kind of frequency converter converts electrical energy supplied by the frequency converter into rotary or linear motion. The motor output can be attached to any number of actuators or mechanical machines to do work.
Machines in assembly, web handling, converting, and packaging industries use both frequency converter types to coordinate working axes and ultimately transform materials into everyday products.
How do frequency converters communicate with other components?
Most modern frequency converters are connected with other components in the control system using communication networks, allowing for improved diagnostics and machine control.
In addition, most frequency converter manufacturers today are moving from proprietary networks toward open networks for servo drives and frequency converters. For example, EtherNet/IP can connect all of a plant's equipment, processes, and information (with one network architecture) to provide real-time information and control.
In fact, Ethernet-based networks allow more information than ever to flow from frequency converter and other intelligent machine components into machine controls and eventually into plant-level control systems. Better integration between servo drives, frequency converters, and controls also makes configuration and diagnostics easier.
How do newer frequency converters differ from designs of the past?
Machines that are modular (with distributed controls) are increasingly common because they make designs more reliable and reusable.
Here, frequency converters (as well as servo drives) are mounted directly onto machines. Moving control hardware closer to the application or onto the machine minimizes a design's physical footprint, simplifies connectivity, and reduces wiring and setup costs by up to 30%.
One caveat: Installing frequency converters at the working parts of a machine exposes them to more abuse. To address this issue, many newer frequency converters include better environmental resistance and ratings — for hot, cold, dusty, damp, sterile, and wash-down environments.
Most frequency inverters today use pulse width modulation or PWM to create a variable output voltage, current, and frequency. Here, a diode bridge rectifier takes alternating current (ac) power from a power source and provides an intermediate direct current (dc) circuit voltage. In the intermediate dc circuit, the dc voltage travels through a low-pass filter. Then, six high-speed electronic switches in the frequency converter's inverter are controlled to create short pulses with the height of the dc bus voltage and of various widths.
By varying the pulse width, converters create an output waveform with an average that is a sinusoidal voltage and current waveform for which frequency can be varied. It is this variable output that is used to control motor speed, torque, or position.
In the intermediate dc circuit, the dc voltage goes through a low-pass filter.
PWM is used in modern converters because it is efficient. The output switches are either on or off, and don't operate in any intermediate states that can increase power dissipation and energy losses.
Motors driven by frequency converters are sometimes fitted with position feedback devices. In these situations, feedback devices improve motor accuracy, dynamic response, and torque production at low speeds.
How do frequency converters differ from servo drives?
Frequency converters typically control velocity or torque. In contrast, servo drives are often used to control motor position — and almost always use a position feedback device on the motor.
PWM output switches are either on or off, a more efficient design than including intermediate states. By varying the width of the pulses, a converter creates an output waveform for which the average is a sinusoidal voltage and current waveform — the frequency of which can be varied. It is this variable output that is used to control motor speed, torque, or position.
That said, recent frequency converter technology advances are increasingly tailored to specific applications — and don't require changes to entire control systems when added. In addition, the traditional assumptions that frequency converters and induction motors only control speed and servo drives and permanent magnet (PM) motors only control position are being challenged. Why?
First, there's more demand for higher motor efficiency in some frequency converter applications — so frequency converters increasingly control PM motors. Second, the better performance of newer frequency converters is rivaling that of servo drives. Finally. the emergence of Ethernet-based networks improves all types of control, including motion and drive control.
Frequency converters and servo drives share some characteristics: A motor connected to either kind of frequency converter converts electrical energy supplied by the frequency converter into rotary or linear motion. The motor output can be attached to any number of actuators or mechanical machines to do work.
Machines in assembly, web handling, converting, and packaging industries use both frequency converter types to coordinate working axes and ultimately transform materials into everyday products.
How do frequency converters communicate with other components?
Most modern frequency converters are connected with other components in the control system using communication networks, allowing for improved diagnostics and machine control.
In addition, most frequency converter manufacturers today are moving from proprietary networks toward open networks for servo drives and frequency converters. For example, EtherNet/IP can connect all of a plant's equipment, processes, and information (with one network architecture) to provide real-time information and control.
In fact, Ethernet-based networks allow more information than ever to flow from frequency converter and other intelligent machine components into machine controls and eventually into plant-level control systems. Better integration between servo drives, frequency converters, and controls also makes configuration and diagnostics easier.
How do newer frequency converters differ from designs of the past?
Machines that are modular (with distributed controls) are increasingly common because they make designs more reliable and reusable.
Here, frequency converters (as well as servo drives) are mounted directly onto machines. Moving control hardware closer to the application or onto the machine minimizes a design's physical footprint, simplifies connectivity, and reduces wiring and setup costs by up to 30%.
One caveat: Installing frequency converters at the working parts of a machine exposes them to more abuse. To address this issue, many newer frequency converters include better environmental resistance and ratings — for hot, cold, dusty, damp, sterile, and wash-down environments.
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