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How to choose the right variable frequency drive?
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How to choose the right variable frequency drive?

Views: 119     Author: Eric     Publish Time: 2022-05-10      Origin: www.bedford.com.cn

      Inverter is the application of frequency conversion technology and microelectronics technology. It is a power control device that controls an AC motor by changing the frequency of the motor's operating power supply. It can save energy, regulate speed, and provide safety protection to the motor. Bedford, the inverter manufacturer since 1993. Is a high-tech enterprise specializing in variable frequency drive research and development, production, sales, and technical services.

      Industrial automation control, we always need to use inverter to convert the industrial frequency power supply into various frequency AC power supply to realize the variable speed operation of the motor. Motors take at least half of the industrial energy consumption, and with the increasing industrial automation, inverters also are being widely used. Therefore, how to choose the right inverter for the motor is a common concern. The following three points are the details of inverter selection:


01 Select inverter according to the operating current

Motor operating current is a key factor in inverter selection. The variable speed drive must meet the output current greater than the actual working current of the motor when working for a long time. Therefore, the operating current characteristic curve needs to be used as a reference basis.

Specifically, the selection is matched in terms of voltage, current, and torque. So to make sure the inverter can work normal, we need to have a comprehensive and detailed understanding of the site's power usage, including the level of the voltage used and the quality of the voltage waveform.

At the same time, we also need to have some knowledge of the load. The performance curve of the load determines the application method of the inverter. The rated current of the inverter for an ordinary centrifugal pump matches the rated current of the motor; the deep water pump requires a larger current.

voltageFour quadrant

02 Select inverter according to the use environment

When selecting the inverter, we should also fully consider the impact of the environment on the inverter:

If the motor at the site requires frequent starting and braking, a braking resistor must be installed, and the size of the braking resistor should be selected according to the power.

If the environment of the factory is harsh, dusty and difficult to dissipate heat, we should choose a high dustproof grade inverter.

If the equipment needs to do aging tests, we should consider using four-quadrant inverters to reduce power loss.

If the work shop has independent DC power, it is possible to use only pure inverter modules to reduce financial investment.

Above all, we should choose different inverters according to different site conditions. If you are interested in the four-quadrant inverters recommended for the aging test mentioned, you can check our latest generation products B503PRO and W505: open-loop vector inverters.


03 Selection of inverter according to the control purpose

General industrial motors are AC induction motors, which can use constant voltage control or constant current control. Depending on the purpose of motor control, the frequency converter can be selected differently.

For example, when a high-speed motor is to be driven, the output current value increases due to the increase in high harmonics due to the small reactance of the high-speed motor. Therefore, it is necessary to use a frequency converter with a capacity slightly larger than the ordinary motor.

For example, when it is necessary to run with a long cable, then we must take measures to suppress the influence of the long cable on the ground coupling capacitance. We can make the inverter capacity to be enlarged by one grade, or install output reactor at the output of the inverter to avoid insufficient output of the inverter.

The selection of an inverter depends on many factors and should be based on the requirements of 3 aspects: operating current, use environment and control purpose. By doing so, we can choose the right inverter for industrial control and balance between production process and production economy.

Textile industry

Injection molding

central air-conditioning

Air compressor   

      Bedford's guide to choosing the right model of inverter. If you need further info and details please don't hesitate to contact us. Detailed parameters of the B503PRO are attached at the end of this article.


B503PRO, General Purpose Vector Frequency Inverter

Digital input

7 circuits, one of which supports   high-speed pulse input up to 100KHz

Analog input

2 circuits (AI1, AI2: 0V~10V or 0/4mA~20mA)

Open Collector output

1 circuit

Relay output

2 circuits

Analog output

2 circuits (AO1: 0/4mA~20mA or 0V~10V, AO2:   0/4mA~20mA)

Control mode

PG-free vector control, V/F control, torque   control (PG-free vector control)

Frequency setting mode

Digital setting, analog setting, pulse setting, multi-speed setting, simple PLC   setting, PID setting, serial communication setting, can realize setting   combination and mode switching

Simple PLC

Simple PLC: 16-stage speed control can be   realized

Multi-stage speed control

16-stage speed

Input phase loss selection


PID control


Swing Frequency Control


Various protection

Over current, overvoltage, under voltage, phase   loss, overload and other protection functions

Built-in brake unit

220V: 0.75 -   22KW built-in, 30-55KW optional

380V: 0.75 - 37KW   built-in, 45-110KW optional

Built-in DC reactor

220V: 11-55KW   built-in

380V: 18.5-110KW   built-in

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About us

Bedford water supply equipment is widely used in high-rise residential buildings, villas, schools, hospitals, large communities, air source heat pump hot and cold water systems, solar water heating systems, water treatment, energy-saving water supply systems for buildings, and other occasions. ​​​​​​​

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