Magnetek Impulse G+ series 4, Техническое руководство

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IMPULSE•G+/VG+ Series 4 Technical Manual
November 2022
Page 19
2.3 Long-Term Storage and Capacitor Reforming
Powering up the VFD every six months is recommended. Over longer periods of time without power, the VFD’s
electrolytic DC bus capacitors require reformation, especially if stored in an area of high temperatures. Capacitor
reforming is required if VFDs are stored without power for more than 2 to 3 years. This process can be avoided by
powering up the VFD bi-annually for 30 to 60 minutes.
NOTE:
Bus cap reforming may not restore full VFD functionality after 2 to 3 years of storage without power.
Variable frequency drives (VFD) 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 VFD’s functionality not be restored after bus cap reforming.
Contact Magnetek Field Service for assistance.
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 should 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 VFDs 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.
2.3.1 Capacitor Reforming Procedure
1. Connect the VFD inputs L1 and L2 to a variac. It is also acceptable to use a three-phase variac or a variable
DC power supply rated for the VFD's nominal DC bus voltage.
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
VFD. If the variac has an output current indication, make sure the current is near zero.
4. Slowly turn the variac up, increasing the 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 VFD. 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.
If any abnormal indications occur during this process, it is recommended that the process be repeated. If problems
persist, the VFD should be replaced.