Long Time Storage - Magnetek Impulse G+ series 4 Instruction Manual

Long Time Storage

Powering up the drives every six 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 to 3 years. This process can be avoided by powering up the drive bi-annually for 30 to 60
minutes.
NOTE:
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 not function after several years without
power. Magnetek recommends replacing the PCBs should the drive's functionality not be restored
after bus cap reforming. Contact Magnetek Service for questions.
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 and 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. Connect the inverter inputs L1 and L2 to a variac.
2. 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.
3. 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.
4. Slowly turn the variac up, increasing the variac's output voltage to nominal rated input voltage
over a time period of 2 to 3 minutes. In other words, ramp the voltage up at a rate of
approximately 75 to 100 volts/minute for 230 VAC units, 150 to 200 volts/minute for 460 VAC
units, and 225 to 300 volts/minute for 575 VAC.
5. Let the output voltage remain at rated voltage for 30 to 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.
6. Once 30 to 60 minutes elapse, remove power.
Bus cap reforming alone may not restore full drive functionality after 2 to 3 years of
IMPULSE®•G+ & VG+ Series 4 Instruction Manual - February 2017
2-5