FAQ# DRV-5WKJK7 Published: 03/14/2006

Question:What are the maintenance recommendations for drives that sit on shelves for a couple years without power? Should the drives be powered up from time to time?
Answer:Powering up the drives every 6 months is quite beneficial. Over longer periods of time without power, the drives electrolytic DC Bus capacitors require reformation especially if stored in an area of high temperatures. Capacitor reforming is required if drives are stored without power for more than 2-3 years. This process can be avoided by powering up the drive biannually for 30-60 minutes.

NOTE: Bus cap reforming alone may not restore full drive functionality after 2-3 years of storage without power.

Inverter drives contain large bus capacitors that have the potential to be reformed. However, printed circuit boards also contain electrolytic capacitors that may no longer function after several years without power. Yaskawa recommends replacing the PCB's should the drives functionality not be restored after bus cap reforming.

Capacitor Storage and their Reforming Process

The electrical characteristics of aluminum electrolytic capacitors are dependent on temperature; the higher the ambient temperature; the faster the deterioration of the electrical characteristics (i.e., leakage current increase, capacitance drop, etc.). If an aluminum electrolytic capacitor is exposed to high temperatures such as direct sunlight, heating elements, etc., the life of the capacitor may be adversely affected. When capacitors are stored under humid conditions for long periods of time, the humidity will cause the lead wires/terminals to oxidize, which impairs their solderability. Therefore aluminum electrolytic capacitors should be stored at room temperature, in a dry location and out of direct sunlight.

In the event that a capacitor has been stored in a high ambient environment for more than 2 or 3 years, a voltage treatment reformation process to electrolytic capacitors may have to be performed. When stored above room temperatures for long periods of time, the anode foil may react with the electrolyte increasing the leakage current. After storage, the application of even normal voltages to these capacitors may result in higher than normal leakage currents. In most cases the leakage current levels will decrease in a short period of time as the normal chemical reaction within the capacitor occurs. However, in extreme cases, the amount of gas generated may cause the safety vent to open.

Capacitors, when used in inverter drives that are stored for long periods of time, should be subjected to a voltage treatment/reforming process as noted below, which will reform the dielectric and return the leakage current to the initial level.

Inverter Bus Capacitor Reforming Procedure:
1. Remove the fuse from the 3PCB tap change card for this procedure.

2. Connect the inverter input L1, L2, and L3 to a variac.

3. Make sure the variac voltage setting is turned down so that when input power is applied to the variac the output of the variac will be at or near 0 Volts.

4. Apply power to the variac, listening for abnormal sounds and watching for abnormal visual indications in the drive. If the variac has an output current indication, make sure the current is very near zero with zero or a steady output voltage applied.

5. Slowly turn the variac up, increasing the variac's output voltage to nominal rated input voltage over a time period of 2-3 minutes. In other words, ramp the voltage up at a rate of approx. 75 – 100 volts/min. for 230 VAC units and 150 – 200 volts/min. for 460 VAC units.

6. Let the output voltage remain at rated voltage for 30 - 60 minutes while keeping close watch for abnormal signs within the inverter. While increasing the variac's output voltage, the current will momentarily increase as current is necessary to charge the capacitors.

7. Once 30 – 60 minutes elapses, remove power and package the drive for shipment.

If any abnormal indications occur during this process, it is recommended that the process be repeated. Otherwise, this completes the capacitor reforming procedure.

Product Information:

Product Group:Inverters/Drives
Product:DC5 Converter, E7 Drive, F7 Drive, G3 GPD503 Drive, G5 Drive 600 Volt, G5 GPD515 Drive, G5HHP Drive, G7 Drive, H5 Drive, J7 Drive, P5 Drive 600 Volt, P5 GPD506 Drive, P7 Drive, PS5 Drive, R3 Drive, RC5 Converter, SS5 Drive, V7 Drive, V74X Drive, V7N Drive, VCD723 Drive, VG3 VCD703 Drive, VH3 Drive, VS mini
Category:Adjustments; Installation; Maintenance; Operation; Reliability

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Please read and understand the product instruction manual before installing, servicing or operating Yaskawa products. FAQ content and illustrations are provided as technical advice to augment the information in manual, not superceed it. It is not possible to give detailed instructions for all types of installation or support activities. The information described in the FAQs are subject to change without notice to improve the product or FAQ. Yaskawa assumes no responsibility for errors or omissions or damages resulting from the use of the information contained in any FAQ. All warnings, cautions and product instruction for product use must be followed. Installation, operation and maintenance should be carried out by qualified personnel. Failure to observe these and other precautions highlighted in the product manuals will expose the user to high voltages resulting in, serious injury or death. Qualified personnel are defined as individuals who are familiar with the installation, starting, operation and maintenance of Yaskawa products of the type described and have proper qualifications to perform the work.