How We Repair Servo Drive Servo Motors Professionally

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We repair and warranty all major AC and DC Servo Motors and Controllers, feel free to call now at 1-877-625-2402 for a free quote or fill out the Servo Motor and Drive Quotation Form. For those of you looking to repair the drive yourselves, our procedure for professional repair is listed below.

For those interested in repairing servo motors and servo drives, it is important to note the extreme care that should be taken prior to conducting any disassembly of a servo motor or servo drive unit.

All servo motor and servo drives are mechanically calibrated between multiple facets of the unit to ensure the proper positioning of the device when it is commissioned. Failure to properly dis assemble a servo motor or drive can actually cause the unit to become unusable in the future.

The inner workings of servo motors and servo drives are both separate, and thus they should be treated separately. This particular article focuses primarily on troubleshooting the servo motor that is connected to the servo drive.

Servo motors are specifically designed with what is known as “feedback” capabilities so that the servo drive can maintain positioning of the motor within fractions of an inch, and many times even more accurate when necessary. Servo motors are specifically designed to withstand high amounts of holding current as well as extremely fast start stop procedures so that accuracy can be maintained at all times.

This feedback connected to a servo motor often comes in the form of an encoder or resolver, depending on the type of encoder or resolver you might have, troubleshooting your servo motor may be impossible. In many cases, manufacturers such as Allen Bradley, or Rockwell, implement a proprietary resolver or encoder feedback so it cannot be repaired without their diagnosis and repair tools. Regardless, there are many more aspects to a servo motor that can go bad other than the encoder or resolver – so it is best to start at those places.

The following is the procedure used by Precision Electric illustrating how to repair servo drive servo motors professionally.

Step 1: Take Notes

This is often a subject that is passed by many individuals who are attempting to repair industrial equipment. When a unit first hits our bench we make note of many important aspects of the equipment including, but not limited too:

    1. Manufacturer
    2. Serial Number
    3. Reason for Service
    4. Urgency (Rush Overtime or Standard)
    5. Visual Inspection of External Device

Step 2: Check The Shaft

It is important at this point to establish whether or not the servo motor shaft has been bent, damaged or broken. If this is the case, a new shaft may need to be ordered or machined in order to recommission the unit. In some cases, a bent shaft cannot even be replaced and this can quickly become a quote for replacement.

A bent shaft on a servo motor can cause extreme wear to the device over time due to vibration and heat. A bent shaft can also cause slip on a gear box and loss in positioning resulting in unexpected faults from the servo drive. You may need to use a caliper to establish the proper positioning of the shaft within the closest accuracy possible.

Step 3: Check The Encoder and Motor Cables

Hopefully the customer sent the communications cable with the unit so you can test the pin-out of the cable to ensure all of the wiring has a strong signal. In instances such as these, you may need to pull up pinout information from the servo motor manufacturing website to ensure you are testing the appropriate cables. In many cases, an encoder cable with have a pin for each channel of A, A not, B, B not, Positive Voltage and Common.

In some cases it will also have a Z and Z not pulse as well as a shield. Of course, not all customer are able to send the cable with the unit because they sent you a spare to repair – if that is the case you are really left with no other choice than to move on to the next step. Finding a bad cable early on is a great way to solve servo motor feedback issues without ever even requiring disassembly of the servo motor.

For the motor cable, you are looking at 3 separate phases, 2 armature wirings and sometimes commutation wiring. Using your meter, test the end of each cable to ensure there are no shorts between any of those connections.

Step 4: Check The Bearings

The shaft coming out of the servo motor should rotate freely with little resistance. This is assuming you have actually disconnected the cables from the original servo drive. The drive often causes resistance when rotating the shaft if it is connected to the servo drive through the motor cables.

If there is “bouncing” when attempting to rotate the shaft then it is likely due to a short within the motor or a bearing beginning to fail. In either case, it is bad and the servo motor will need to be disassembled for further diagnosis.

Step 5: Test The Motor For Shorts

This step is essential to further diagnostics. At this point you need to test the motor to ensure there are no shorts within it. Using your meter, you will want to test from phase to phase to ensure the connections are open. Do the same with the armature connections. There should be no shorts between them. If you find a short at this point it is likely the cause of the failure.

Servo motor shorts can be caused from a variety of reasons including contamination, overheating and wear and tear – the only real way to find the source of the short is to disassemble the unit and establish the cause of failure.

Step 6: Rotate the Motor

Assuming the prior tests have all passed, apply a small voltage starting from 0 volts to the armature winding of the servo motor. Slowly increase this voltage using your variable power supply until the shaft begins to turn. It is at this point you can further evaluate whether there is unnecessary vibration of the servo motor during rotation or whether the shaft appears to wobble or “bounce” due to a bent shaft or bad bearing.

In any case, rotating the motor prior to disassembling it is a good idea if it is possible – this will let you know that the servo motor at least functions on some level prior to establishing the original cause of the failure.

Step 7: Contact the Customer

If everything has tested healthy at this point it may be a good idea to contact the customer and get more details as to the original cause of failure. It is quite common with servo motor and servo drive applications that the cause of the failure was external to the motor itself. The servo motor often was doing what its job was intended to do, stop within a fraction of an inch of inaccuracy and fault.

Most people do not realize that an outside application change or environmental change can cause fluctuations in the configuration of the servo motor that can cause faults. It is also important to establish whether or not the servo motor was properly tuned for the application to begin with. Sending a field service tech and getting the servo motor properly tuned may cause the issue to go away.

Step 8: Carefully Disassemble The Servo Motor

When we say carefully, we mean carefully. You should mark the location of every detached piece with a punch to or file to ensure you reassemble the unit exactly as it was assembled. Failure to do this will often cause the servo motor to produce exceeding level of vibration which can cause further failures or not function at all. It is also sometimes wise to take photographs as you are disassembling the unit so you have a log of how the servo motor looked prior to each phase.

This section cannot be emphasized enough, as you remove more and more pieces of the servo motor take a closer visual inspection of each element within the motor including the commutator, armature, shaft and brushes. Try to locate any possible cause of failure before continuing to disassemble the drive. The sooner you find the cause of failure at this point the better, as it means less reassembly is required.

Once you have established the cause of failure your response will depend on both the manufacturer of the servo motor and the original cause. In many causes, certain brands will not allow you to purchase parts for their servo motors and a replacement may be required. There are certain aspects of a servo motor that can be replaced or repaired by third parties such as the armature winding or brushes.

Step 9: Send a Tech

If the customer cannot establish failure on any other aspect of the machine and the servo motor appears to test fine and be in good shape after disassembly, then it may be necessary to send a field service technician on site to establish cause of failure.

Our field service techs are trained to troubleshoot any issue ranging from standard AC Motor Speed Controllers to advanced robotics and PLCs. They are trained to establish cause of failure as quick as possible.

Conclusion:

Precision Electric has used these techniques over the past 20 years to establish one of the best reputations for the industrial service industry. These methods for testing servo motors have been well established and have resulted in the repair or replacement of thousands of industrial servo drive servo motors.

 

Variable Frequency Motor Drives

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Variable frequency motor drives are also known as motor drives, variable frequency drives, VFD’s, variable speed drives, adjustable frequency drives, AFD’s, adjustable speed drives and ASD’s. Motor drives are solid state motor control systems used to regulate the speed of alternating (AC) electric motors. Motor drives are mainly used to reduce energy consumption on electric motors for industrial manufacturers.

Motor drives operate as load controls within applications that may accomplish up to 50% reduction in energy costs by speed reduction on applications where the full speed (RPM) of the electric motor is not required. Motor drives are used in AC Servo Systems, Air Compressors, Conveyor Systems, Lathes, Mills, Plastic Extrusion, Slitter Lines, Food Processing, Waste Water Treatment Systems, Submersible Pumps, HVAC Fans and Blowers, and many more AC motor applications.

Many manufacturers apply motor drives with rotating equipment to reduce amperage spikes upon start up of large electric motors. Choosing the right motor drive for an application will benefit rotating equipment by providing less wear on the electric motor where applied. This is accomplished by adjusting the acceleration and deceleration time of electric motors. Adjusting the acceleration and deceleration time of an electric motor will greatly increase the lifespan of an electric motor. Motor drives provide the ability to control the frequency of starting and stopping of an AC electric motor. This ability provides a means by which an AC electric motor is only operating when needed for the equipment it’s rotating, and electric motors have a longer lifespan if they are not continuously operating when they don’t need to be.

Approximately one third of the world’s electrical energy is supplied by electric motors in fixed-speed centrifugal pump, fan, and air compressor applications. These fixed-speed applications hardly ever require the full load speed (RPM) of the electric motor they’re operating. By integrating motor drives to these applications, the motor speeds are reduced, and power costs can be reduced by 50% or more. Technology has reduced cost and physical size of motor drives, and has improved performance through advances in semiconductor switching devices, simulation, control techniques, and control hardware and software.

Power Savings With Motor Drives

The majority of motor drives in the market today contain electronic circuitry that converts 60 Hertz Line power into direct current. The motor drive converts this line power into a pulsed output voltage that duplicates varying alternating current to a desired frequency (speed). A properly applied motor drive when paired with an AC electric motor, will significantly reduce operating costs. This is particularly true for variable torque loads such as Fans, Blowers, and Pumps. Blowers, for example, are often used with dampers to control air flow.  These dampers may operate either manually or automatically.  When dampers are closed, 50% of the electric motor current will drop to approximately 60% of Full Load nameplate current.  By utilizing a motor drive in this application, current draw in the motor will be reduced 30% for every 10% drop in speed. The same electric motor operating from a motor drive at 50% speed, will draw approximately 20% of the full load current.

Types Of  Motor Drives

Volts Per Hertz motor drives are the most common type of drive and are known as a V/Hz drives, or volts by hertz drives. V/Hz motor drives are used in applications such as fans, pumps, air compressors, and other related applications where high starting torque is not required. V/Hz drive applications typically do not require full torque when the AC motor is operating at less than the base speed (RPM) of the electric motor. V/Hz drives are the most inexpensive type of motor drive. V/Hz drives do not provide full motor torque at low RPM.

Open-Loop vector motor drives are also known as “sensorless vector” drives. Open loop vector drives adapted the name “sensorless vector” because they do not use an external encoder for speed feedback to the motor.  Open loop vector drives are used in applications where high starting torque and full torque at low speed (RPM) is required. Open-Loop vector drives operating a motor a zero RPM should not be used on crane or hoist applications. Most open-loop vector drives are used on CNC machines, mixers, mills, lathes, and other applications where high starting torque or full torque at low RPM is needed. Open loop vector drives are usually more expensive than V/Hz inverter drives.

Closed-Loop vector motor drives are used in applications where precise speed control (0.01%) is needed, or in applications where extensive programming is needed. Closed-Loop vector drives use an encoder on the motor to provide constant shaft position indication to the drive’s microprocessor. The encoder feedback allows the drive microprocessor to constantly control torque no matter how many RPM the motor is operating at. Closed-Loop vector motor drives are used to provide the motor to operate at full torque even at zero RPM. Closed-Loop vector drives are commonly used on hoist and crane applications because crane and hoist motors must produce full torque prior to it’s brake being released, or the load will drop and it will not be able to stop.

To learn more about motor drives or for motor drive repairs and replacement quotes, contact Precision Electric, Inc.

What Is The Default Password For An AC Tech SMVector VFD?

What Is The Default Password For An AC Tech SMVector VFD?

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All AC Tech SMVector drives come equipped with a default password to protect the drive from operators changing parameters without the programmers consent. Although this process can be confusing the first time you open your AC Tech SMVector VFD, or Variable Frequency Drive, it is easy to do once you’ve done it once.

Password protection is becoming more and more prominent in the world of Variable Frequency Drives and the SMVector illustrates this process right out of the box. The purpose of protection is to keep the program within the drive protected from outside modifications or to allow OEMs to protect their proprietary configurations when selling a machine.

Many customers also opt to purchase a EPM module for their SMVector drive to keep their configuration files backed up to a separate module, just in case of a drive failure or EPM program failure. Whatever the reason for accessing the parameters, the process of accessing the parameter menu is extremely easy.

Abstract:

This article illustrates how to access the parameter menu using the keypad on the SMVector drive with the default password.

What Is The Default Password For An AC Tech SMVector VFD?:

1. Power up your SMVector drive, the default screen that is displayed is typically the Stop screen as shown below. Note: You can access the parameter menu while the drive is in run as well, but not all parameters can be changed while in run mode.

Step 1 - SMVector Keypad LCD - Stop

2. Press the Menu button.

Step 2 - SMVector Keypad LCD - Menu Button

3. The word PASS will flash on the screen.

Step 3 - SMVector Keypad LCD - Password

4. After the PASS screen is displayed, you should be greeted with four zeros to enter your password. Hold the Up arrow key to increase the number.

Step 4 - SMVector Keypad LCD - Press And Hold Up

5. Once you have reached the default password of 0225, press the Menu button again to enter it.

Step 5 - SMVector Keypad LCD - Enter Default Password

6. You should be greeted with the P100 parameter, press the up arrow key to scroll through the parameters and continue to access the parameters with the Menu key.

Step 5 - SMVector Keypad LCD - Parameter Menu

Conclusion:

If you run into any issues when accessing your SMVector parameter menu, feel free to contact us for support. Precision Electric takes pride in offering technical support services to all of their existing or future customers.

How a VFD Works

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How A VFD Works: A variable frequency drive is also known as a VFD, variable speed drive, adjustable speed drive, electronic motor controller, or an inverter.  How a VFD Works: Every VFD is unique with its own component characteristics so how each VFD works is dependent upon components within the VFD. Most VFDs integrate a solid state electronics controller consisting of a bridge rectifier, a converter, and an inverter module.

Voltage-source inverter drives are the most common type of VFDs. These drives convert AC line input to AC inverter output. There are some applications that use common DC bus and solar applications. These type of drives are configured as DC to AC drives. The bridge rectifier converter for volts per hertz drives is configured for 3 phase AC electric motors. Volts per hertz drives use a capacitor to smooth out the converter DC output ripple and provides a solid input to the inverter.

This filtered DC voltage is converted to AC voltage output using the inverter’s active switching elements. VSI drives provide higher power factor and lower harmonic distortion (noise) than phase controlled current source inverters and load commutated inverters drives. The drive controller can also be configured as a phase converter having single-phase converter input and three-phase inverter output. Controller advances have allowed increased voltage and current ratings and switching frequency of solid-state power devices over the past 50 years. VFDs were first introduced in 1983, and the insulated gate bipolar transistor has in the past 20 years become the standard for VFDs as an inverter switching device.

In variable-torque applications using Volts per Hertz (V/Hz) drive control, AC motor specifications require that the voltage magnitude of the inverter’s output to the motor be adjusted to match the required load torque in a corresponding V/Hz relationship. For 460 VAC, 60 Hertz electric motors, this V/Hz relationship would be 460/60 = 7.67 V/Hz. While acceptable in a wide range of different applications, V/Hz control is sub-optimal in high performance applications. High performance applications requiring low speed control, demanding high torque, dynamic speed regulation, positioning, and reversing load demands, there are open loop VFDs and closed loop VFDs would be desired over V/Hz VFDs.

How a VFD Works – Manufacturing

Many manufacturers will apply variable frequency drives to rotating equipment to reduce amperage spikes upon start up of large electric motors. Choosing the right VFD for an application will benefit rotating equipment by providing less wear on the electric motors where applied. Adjusting the acceleration and deceleration time of electric motors can extend the lifespan of an electric motor. Variable frequency drives provide the ability to control the frequency of starting and stopping of an AC electric motor. This ability allows an AC electric motor to only operate when needed for the equipment it’s rotating, and electric motors have a longer lifespan if they are only running when they need to be.

Approximately one third of the world’s electrical energy is supplied by electric motors in fixed-speed centrifugal pump, fan, and air compressor applications. These fixed-speed applications hardly ever require the full load speed (RPM) of the electric motor in which they’re operating. By installing a VFD to these applications, electric motor speeds are reduced, and power costs can be reduced by 50% or more. Technology has allowed cost and physical size reduction of variable frequency drives, and has improved performance through advances in semiconductor switching devices, simulation, control techniques, and control hardware and software.

How a VFD Works – Power Savings

The majority of variable frequency drives in the market today contain electronic circuitry that converts 60 Hertz Line power into direct current. The variable frequency drive converts this line power into a pulsed output voltage that duplicates varying alternating current to a desired frequency (speed). A properly applied VFD when paired with the correct electric motor will significantly reduce operating costs for manufacturers. This is particularly true for variable torque loads such as fans, blowers, and pumps. Blowers are often used with dampers to control air flow; these dampers may operate either manually or automatically. When dampers are closed, 50% of the electric motor current will drop to approximately 60% of full load nameplate current. By utilizing variable frequency drives in blower applications, the current draw of the motor will be reduced 30% for every 10% drop in speed. The same electric motor operating from an AC variable frequency drive at 50% speed, will draw approximately 20% of the full load current.

Please watch our YouTube Video to learn more about how a VFD works. For VFD repair and replacement quotes, contact Precision Electric, Inc.

Indramat Servo Motor Repair

Indramat Servo Motor Repair

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Indramat servo motor repair is less expensive than Indramat servo motor replacement. Indramat servo motor repair should only be performed by an electrical technician with training and experience. Most Indramat servo motors have unique testing procedures dependent upon their model, features, operations, and prints; But the general process is performed by a technician who follows standard test procedures. Technicians performing Indramat servo motor repair should go through an extensive evaluation process to ensure nothing is overlooked. Servo motor repairs should be initially inspected for cosmetic damage and taking photos prior to further processing is suggested.

All nameplate and preventative maintenance info should be collected by the repair technician and safely stored for future reference. Once these initial steps are complete, the Indramat servo motor should be meter tested before test running on a control panel; Meter testing is to prevent further damage to parts, winding, and insulation. The servo motor should then be connected to a test stand to check EMF (electromagnetic frequency), encoder or resolver feedback, and commutation alignment; These standard tests are to ensure functionality once the motor is installed into production. Servo motor repairs also need to be tested with an oscilloscope to create an operation print. Once an operation printout is generated, the technician will check for connection issues, magnet failure, winding failure, and perform a 100% component test.

Indramat Servo Motor Repair  – Steps

  • Visual inspection of cosmetics
  • Take photos of unit
  • Gather nameplate data and shaft dimensions
  • Inspection of all electrical and mechanical servo motor parts
  • Re-magnetize magnets when necessary
  • Re-manufacture output flange using original flange and factory dimensions
  • Repair or rewind servo motor windings, insulation, connections
  • Steam clean and bake
  • Replace brush holder and brushes (or repair brush holder if obsolete)
  • Grounded to electrical testing
  • Surge testing of every winding to at least 1500 volts
  • Armature bar to bar test; to determine any shorts or opens within the winding
  • Servo motor alignment
  • Installation of high-grade sealed bearings
  • Installation of double lip seals in the front flange
  • Replacement of all old seals, O-rings, gaskets and connectors
  • Two part epoxy coating for an added protection

Once testing is complete, the servo motor technician reassembles the unit for final testing. During the final test procedure, technicians should connect the motor to an inverter drive with and without a load. Running the servo motor on an inverter is to ensure complete functionality before returning to customer. Final testing of servo with an inverter also allows verification that the servo motor can operate at full voltage and withstand full load amps of the motor specifications. It’s also suggested that repair shops work closely with all servo motor manufacturers. Working closely with servo motor manufacturers allows for access to data sheets that are needed to ensure that the the servo motor performs equal to, or better than, the original equipment manufacturer standards.

Some repair shops only require technicians to perform a few of these procedures but all of them are suggested by Precision Electric. Most repair shops who offer Indramat servo motor repair do not even perform the repair in their facility; Instead, they outsource the repair to a third party such as Precision Electric. Precision Electric recommends technicians who are involved in repair decisions, verify that the company you’re sending equipment to is the same company who performs the repair. Using a third party Indramat servo motor repair shop is risky, more expensive and has a longer lead time than going directly to the repair source.

Servo motor repairs performed by Precision Electric includes a 12 month in-service warranty. The Precision Electric in-service warranty begins the day the servo motor is put into production and ends 12 months later.

For more information on Indramat servo motor repair and replacement, contact Precision Electric.

Single Phase Power To Three Phase

Single Phase Power to Three Phase – Solutions For The Electric Motor User

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When someone needs to run a three phase electric motor and only single phase power is available, they look for a solution. There are a couple options to go from single phase power to three phase. This article will discuss options available for going from single phase power to three phase., pros and cons for each option, and, links to our website for products that will go from single phase power to three phase. There are two different methods to go from single phase power to three phase:

  • Variable Frequency Drives (VFD’s)
  • Rotary Phase Converters (RPC’s)

When going from single phase power to three phase, either a variable frequency drive or rotary phase converter is required. Variable frequency drives come with a number of different single phase input for three phase output options. Variable frequency drives that go from single phase power to three phase are available in a wide range of voltage and power ratings: From 120 Volt single phase input for 240 Volt three phase output, up to 1.5 horsepower; To 208-240 Volt single phase input for 240 Volt three phase output, up to 3 horsepower.

Variable frequency drives can also be derated to run three phase motors above 3 HP from single phase supply. Derating a VFD allows customers with 208-240 volt single phase power the ability to run 240 volt three phase equipment. Derated VFD’s are available up to 20 HP for 208-240 Volt single phase supply. Derating a VFD incorrectly for single phase supply can be easily avoided by contacting an experienced technician before purchasing equipment.

Rotary phase converters (RPC’s) will change single phase power to three phase but RPC’s are heavy and use many moving parts. RPC’s are old technology but RPC’s will be around for years to come because some applications that go from single phase power to three phase cannot use a VFD; VFD’s can go from single phase to three phase for electric motor driven applications; but RPC’s can go from single phase to three phase on applications with and without electric motors.

Single phase motors cannot be used on variable frequency drives. When customers with single phase motors want to control the speed of their electric motor, the only option available is to replace the single phase motor with an equivalent three phase motor, and then apply a variable frequency drive to that three phase motor. For VFD and RPC repair and replacement quotes, contact Precision Electric.

 

Convert Single Phase to Three Phase

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Single Phase to Three Phase Converter

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Variable frequency drives can be used as a single phase to three phase converter for AC electric motors. Most variable frequency drive manufacturers design products up to 3 horsepower to convert single phase to three phase. Precision Electric offers solutions for customers looking to convert single phase to three phase electric motors that exceed 3 horsepower. Precision Electric also offers variable frequency drives to convert 120 volt single phase to 220 volt three phase for AC electric motor applications through  the 1.5 horsepower range.

De-rating for 1 Phase Supply

For AC electric motor applications that exceed 3 horsepower, some variable frequency drives can be de-rated for single phase power supply. Lenze Americas is a variable frequency drive manufacturer in the United States that offers drive products above 3 horsepower that can be de-rated for single phase power supply. Lenze uses a simple formula to de-rate a three phase drive for single phase power supply. The formula Lenze Americas uses to determine the size drive they manufacture and apply on such applications, is as follows:

  1. Single Phase to Three Phase ConverterCheck the AC electric motor nameplate full load current (amps) and multiply it by 1.73.
  2. Choose a three phase Lenze drive that is good for the new current rating.
  3. Upon installation, wire the single phase supply to the input of terminals 1 and 2 on the Lenze converter.
  4. Leave 3rd terminal on the input of the converter open.
  5. Install the 3 electric motor leads on the output of the Lenze converter.

Never wire or install a variable frequency drive without proper training. Call a qualified electrician to install and wire a variable frequency drive for industrial AC electric motors. Call or email Precision Electric today for technical support or to correctly size a variable frequency drive for a single phase to 3 phase converter.

 

 

Lenze AC Tech SMVector Drive Acceleration Time Parameter

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In this article I will discuss how to program the Lenze-AC Tech SMVector acceleration time parameter. The Lenze-AC Tech drive acceleration time parameter is very simple to change.

The Lenze AC Tech SMVector drive acceleration time parameter default is 20 seconds for the motor to reach full speed (rpm). For most applications, 20 seconds is not efficient. Most applications using the Lenze-AC Tech SMVector desire an acceleration time of about 4-5 seconds.

To change the Lenze-AC Tech SMVector acceleration time parameter you will first need press the “M” button on the drive keypad. Once you’ve pressed the “M” key, The “PASS” flashes on the screen for a couple seconds and is replaced with “0000”.  Using the arrow keys this should be changed to the password.  Default is “225”.

After you’ve entered the password into your Lenze-AC Tech SMVector drive you will need to press the “M” key again. Now the screen will say “P100” which means you can now change the acceleration time parameter on your Lenze-AC Tech SMVector drive.

Simply press the arrows on keypad until you come to “P104” which is the acceleration time parameter for the Lenze-AC Tech SMVector drive. Once you see “P104” on the drive screen, press the “M” key again. Now use the arrow keys until you’ve reached your desired acceleration time for your Lenze-AC Tech SMVector drive application.

 

 

VFD Single Phase to Three Phase

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VFD Single Phase to Three PhaseA VFD (variable frequency drive) is an electric motor drive and although it will convert single phase to three phase it should never be used as a power source for control circuits, instrumentation circuits, or to operate other electronic components. The solution should be to isolate and feed the machine control circuit from a separate single phase source and feed the motor from the VFD output. Control circuits are almost always single phase even when the machine input is three phase. VFD’s that are rated for three phase input must be properly rated when single phase input is used.  Mains (input) current will be much higher when single phase power is applied to three phase rated equipment. Components within a three phase VFD of the same horsepower rating will most often not be rated for enough current and will fail. A mathematical calculation based upon the motor full load current will determine which VFD to use for the application. When applying single phase to a three phase rated drive, the horsepower of the drive will always be a higher rating than the motor horsepower rating.

Installation and Commissioning

A contactor or transition switch should never be used on the output of a VFD. Wiring from the VFD output terminals should go directly to the motor. A contactor may be used on the input but never on the output. Properly rated circuit breakers or fuses should always be used on the input of a VFD. Motor rated circuit breakers and fuses will allow too much current to pass for too long. Electronic components are less tolerant of short term over current conditions than motors. This information is found in the VFD User Manual. Installation of a VFD and other related equipment should only be performed by qualified personnel. VFD programming is typically easy for most applications. Programming for an application can usually be successfully performed once user manual has been read.

 

 

 

 

VFD Speed Controller

VFD Speed Controller

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A VFD speed controller is also known as a variable frequency drive, variable speed drive, adjustable frequency drive, VFD or, an inverter.

A VFD speed controller is a solid state electric motor control system, designed to control the speed of an electric motor. A VFD speed controller can reduce energy costs up to 50% by speed reduction on electric motors where the full speed of the electric motor is not needed. VFD speed controller functions allow an AC electric motor to only operate when needed, which allows an electric motor to last longer. Technology has allowed VFDs to reduce in cost and physical size, and has improved performance through advances in semiconductor switching devices, simulation, control techniques, control hardware, and software.

Approximately one third of electrical energy in the world is supplied by electric motors in fixed-speed centrifugal pump, fan, and air compressor applications. These fixed-speed applications do not usually require full load speed of the electric motor they’re operating. By installing a VFD speed controller to these applications, electric motor speeds are reduced and power costs can be reduced by 50% or more. Properly applied VFD speed controllers with electric motors will also significantly reduce energy costs for variable torque loads such as fans, blowers, and pumps. Blowers are often used with dampers to control air flow that operate either manually or automatically.  When dampers are closed, 50% of the electric motor current will drop to approximately 60% of full load nameplate current. By utilizing VFD speed controllers in blower applications, the current draw of the motor will be reduced 30% for every 10% drop in speed. Electric motors controlled by VFD speed controllers at 50% speed will draw approximately 20% of the electric motor full load current.

VFD speed controllers are also used on rotating equipment to reduce amperage spikes upon start up of large electric motors. Adjusting the acceleration and deceleration time of electric motors can extend the lifespan of an electric motor. Using a drive on an electric motor provides the ability to increase or decrease the frequent starting and stopping of an AC electric motor. Limiting the starting and stopping of a motor, and controlling the ramp up and ramp down speed of a motor, allows for decreased wear and extended lifetime of the motor. VFD speed controllers are used in AC servo systems, air compressors, conveyor systems, lathes, mills, plastic extrusion, slitter lines, bottlers, packaging lines, pharmaceutical production, food processing, HVAC systems, waste water treatment systems, submersible pumps, fans, blowers, and many more electric motor applications.

To learn more about VFD speed controllers, or, for drive repair and replacement quotes, contact Precision Electric, Inc.