Reform Capacitors to Keep Your Spare VFDs Ready for Use

Reform Capacitors to Keep Your Spare VFDs Ready for Use

Having spare VFDs on hand can help reduce the amount of downtime when a failure occurs, but these spares require regular maintenance to keep them ready for use.

When VFDs are stored for long periods of time, typically 12+ months, the internal chemistry of the DC bus capacitors begins to deteriorate if power is not applied.  Formed when voltage is applied to the capacitor, its oxide layer acts as an insulator preventing shorts from occurring. In storage, this layer can degrade.

If the VFD is not powered up slowly to recondition the DC bus capacitors and prepare it for operation under full load, it could result in a catastrophic failure and render it useless. To help maintain your spare inventory, French Gerleman now offers a Bonitron M3628PCF Portable Capacitor Former for rent allowing you to reform your VFDs on site.

 

How often do capacitors need to be reformed?

Most manufacturers recommend an annual power up of all drive modules to insure capacitors are always in an operable state. Consult the manufacturer’s guidelines for specific instructions for your specific VFDs.

 

 

 

Why rent the Bonitron Portable Capacitor Former?

The M3628PCF Portable Capacitor Former can reform capacitors by slowly increasing the DC bus voltage to allow the internal chemistry to readjust at a safe rate. There are digital displays to show the voltage levels and current. The Capacitor Former operates from standard 110-240VAC supply and can also be used as a variable DC power supply for recharging capacitors, or discharging capacitors for maintenance.

Because it comes with wheels and an extendable handle, it is easy to take with you wherever you need it.  It is only 10.5” tall by 18” deep by 22” wide, which makes it convenient to use.

Renting a Bonitron M3628PCF Portable Capacitor Former may be the right solution to make sure your spare VFDs are ready for operation when needed. If you are interested in renting a Bonitron M3628PCF Portable Capacitor Former or have any questions, please contact your French Gerleman Account Manager or Power Control Product Manager.


Are You Correctly Applying Line & Load Reactors on VFDs?

Today’s electronic equipment requires clean, consistent power for optimal performance.  The presence of power distortions between VFDs and motors can damage equipment, jeopardize productivity, and decrease profitability.

We see line and load reactors are often applied on AC variable frequency drives (VFD) without a solid understanding of when and why they should be used. VFDs solve a host of industrial motor control issues, but can introduce power quality problems to the electric grid and/or the VFD-controlled motor.

Eliminate the worry and headaches caused by poor power quality from VFDs by using solutions from MTE. Their products are designed to absorb everyday power line disturbances that can damage or shut down VFDs and other sensitive equipment.

What is a Reactor?

Essentially a reactor is an inductor. Physically, it is simply a coil of wire that allows a magnetic field to form around the coil when electrical current flows through it. More loops give a higher inductance rating. Typically, a ferrous material such as iron is added as a core to the winding. This concentrates the lines of magnetic flux making a more effective inductor. Reactors can be applied to both a VFD’s input and output, but the reasons for application differs.

Harmonic Distortion

VFDs create waveforms that contain harmonic distortion. Harmonics can cause many problems such as: increasing the utility current required to power the system resulting in the need for larger wires, transformers and circuit breakers; increases the motor’s operation costs; causes the overheating of components; inaccurate power measurements; nuisance trips; and telecommunication interference.

Adding an input line reactor helps reduce the creation of harmonics by smoothing out the input waveform. Another reason to add an input line reactor is to help protect the input semi-conductors from transient voltage spikes. This is very important on drive systems that do not utilize an isolation transformer. Compared to the overall cost of a VFD installation, an input line reactor is a small investment to help protect a VFD and provide a reduction in total harmonic distortion.

Peak Voltages & Rise Time

On the output side of a VFD, reactors are used for very different reasons. VFDs vary the speed of a motor by simulating a sinusoidal waveform with pulse width modulation (PWM). The PWM waveform is essentially a square wave created by fast switching on/off of the output semi-conductors (IGBTs). With every on/off transition there is a momentary voltage spike of up to 1400 volts. These spikes can create issues such as reflected wave, corona, and capacitive coupling. Applying an output reactor helps to smooth out the PWM waveform, reduce the voltage spikes and reduce common mode voltage. A reduction in voltage spikes and common mode voltage can help to reduce motor insulating heating and the creation of bearing currents.

Common Mode

Another issue that VFDs can create is common mode voltage which can cause a motor to break down over time. Common mode is created due to an imbalance of voltage in the three-phase output with respect to ground. This voltage seeks a path back to ground or the source it was created (in the case of a VFD, the DC bus). Many times this path to ground is through the motor bearings which can cause arcing and pitting in the bearing raceways and ultimately bearing failure. Applying an output reactor, or dV/dT filter, helps to balance the three-phase output thus reducing the common mode voltage.

The dV Sentry™ Filter from MTE is a revolutionary solution for motor protection. With its unique all-in-one design, the dV Sentry provides common mode reduction, peak voltage protection and rise time reduction. Its small footprint and easy terminations make installation faster and easier. It runs quietly and radiates less heat than previous filters.

French Gerleman stocks MTE line and load reactors. If you have further VFD related questions, please contact your French Gerleman Account Manager.