The Hidden "Expiration Date" on VFDs: Why We Reform Our Inventory (And Can Do Yours Too)

When you buy a Variable Frequency Drive (VFD), like the Teco A510 series we stock, you expect it to work the moment you power it up. But did you know that VFDs sitting on a shelf for too long can suffer from internal chemical degradation? Here is how we ensure every drive we sell is "fresh," and how we can help you save your own spare parts inventory from catastrophic failure.

The Problem: Electrolytic Capacitor Aging

The DC bus capacitors inside a VFD are like batteries; they rely on electrolytes / dielectric films. When a drive sits unpowered for long periods (typically six months to two years) the internal chemistry of these capacitors changes. The oxide insulation layer inside the capacitor begins to deteriorate.

If you take a drive that has been sitting for three years and suddenly hit it with full line voltage, the capacitors may have excessive leakage current. This can cause them to overheat rapidly and fail, potentially destroying the drive before it even spins a motor. As noted in technical literature, "Capacitors stored for long periods of time also display chemistry changes, which may cause them to fail if full voltage is suddenly applied".

The Solution: Our "Fresh Stock"

At our warehouse, we don't just stack boxes; we maintain them. To ensure the Teco A510 drives you buy from us are ready for immediate duty, we follow a Capacitor Reforming schedule using the Bonitron M3628ACF Automatic Capacitor Former.

How We Do It: The "Profile Charge"

We utilize the Bonitron M3628ACF's digital "Profile Charge" mode. This is a process that incrementally increases the voltage on the capacitor, pausing at specific steps to allow the oxide layers to heal safely.

• Step Voltage: We slowly ramp up the DC bus voltage, often in increments of roughly 10% of the rated voltage.
• Hold Times: The system holds the voltage at each step, and eventually at the final voltage, for a designated period (often 20+ minutes) to ensure the reforming process is complete.
• Automatic Validation: Once the cycle is done, the unit automatically discharges the drive and calculates the capacitance to verify the health of the component.

This ensures that when you unbox a drive from us, it acts like it just rolled off the factory line.

New Service: We Come to You!

Do you have a "boneyard" or a critical spares room at your industrial facility? If you have VFDs that have been sitting on your shelves for more than two years, they are at risk.

We are now offering an On-Site Inventory Reforming Service. Because the Bonitron M3628ACF is designed as a portable field unit, our technicians can come to your facility and reform your drives right on the shelf.

Why Schedule This Service?

• Risk Mitigation: Avoid the nightmare scenario of pulling a spare off the shelf during a 2 AM breakdown, only to have it fail upon power-up.
• Verification: Our equipment measures capacitance and stores the data, providing you with a health report for your inventory.
• Cost Savings: Reforming a drive is a fraction of the cost of replacing one before it even has seen service.