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Expert Services

Variable Frequency Drive (VFD) Repair

High-power motor drive diagnostics, IGBT rebuilding, and dynamic load testing.

Service Overview

Variable Frequency Drives (VFDs) regulate AC induction motors across all industrial applications. Running under high electrical load and in hot, dusty factory environments, VFD components eventually fail. Common failure spots include the input bridge rectifier, DC bus capacitors, output IGBT transistors, and main control cards. We provide certified VFD repair up to 500kW, testing every drive under load to ensure long-term stability.

Supported Hardware Series & Models:

ABB (ACS310, ACS550, ACS800, ACS880)

Siemens (Sinamics G120, Micromaster)

Danfoss (VLT Series)

Schneider Electric (Altivar ATV320, ATV630)

Delta (VFD-M, MS300)

Yaskawa (V1000, A1000)

Rockwell PowerFlex

Common Failure Modes & Diagnostic Codes

Technical Reference Sheet for Engineers

Code / Symptom	Probable Cause	Engineering Remedy
DC Link Overvoltage	Excessive regenerative energy from motor deceleration, or failed dynamic braking resistor	Optimize deceleration ramp, test external braking resistors, and replace braking chopper IGBT if damaged.
DC Link Undervoltage	Phase loss in incoming power, failed main contactor, or degraded DC filter capacitors	Check incoming AC line fuses, measure DC bus voltage, replace bypass charge relay and dried-out capacitors.
Overcurrent / Short Circuit	Short circuit in motor windings, output cable leakage, or shorted IGBT module	Perform insulation test on motor using a Megger, check VFD output terminals, and swap damaged IGBT module.
Overheating (OH)	Blocked heatsink fins, failed cooling fans, or faulty internal temperature thermistor	Clean heatsink, replace high-CFM industrial fans, and replace the thermal sensor on the heatsink substrate.

Our Premium 6-Step Component-Level Repair Process

How we restore electronic components to manufacturer specifications

Incoming Visual & Thermal Inspection

Every unit is registered and subjected to high-definition visual inspection and thermal scanning. We identify blown trace lines, scorched resistors, swollen capacitors, and signs of liquid ingress before applying any power.

In-Circuit Analog Signature Analysis

Using advanced Tracker/Signature Analyzers (such as Huntron Trackers), we test passive components (resistors, diodes, capacitors, inductors) and active ICs while in-circuit. This safe, power-off testing compares component electrical signatures against known-good standards.

Semiconductor Power-Stage Diagnostics

For VFDs and servo drives, we test the high-power rectifier and IGBT inverter stages. We check the gate-drive circuit paths, desaturation protections, and replace gate optocouplers to prevent catastrophic future failures.

Microscopic Solder & SMT Reflow

Using ISO-certified temperature-controlled desoldering stations, our IPC-trained technicians replace damaged components. We execute precision micro-soldering under stereo-zoom microscopes for multi-layer PCBs.

Controlled Bench & Load testing

After repair, units are powered on via variable-voltage current-limiting power supplies. We run full closed-loop tests under real load conditions—testing communication links, analog/digital feedback loops, and thermal efficiency.

Final QC Certification & Protective Coating

The repaired PCB is cleaned in an ultrasonic chemical bath to remove flux residues. We apply a high-grade conformal coating to protect against moisture, dust, and corrosive industrial oils before releasing the unit with our warranty.

ISO 9001:2015 Certified

Why Choose Usha Engineering?

26+ Years of B2B Expertise

Established in 2000, we possess over a quarter-century of hands-on industrial electronic repair experience. We are an ISO 9001:2015 Quality Management System certified company.

Up to 70% Cost Savings

Repairing high-end industrial controllers and drives with Usha Engineering is significantly more cost-effective than purchasing expensive new OEM replacement units, which also require configuration.

Advanced Component-Level Lab

Our Panchkula HQ facility features state-of-the-art diagnostic equipment including logical analyzers, digital oscilloscopes, curve tracers, thermal imagers, and dedicated load test benches.

Pan-India Logistics & Quick Turnaround

We accept units shipped via secure courier from anywhere in India, offering express 48-hour turnarounds for critical breakdowns to minimize factory downtime.

Industries We Serve

Steel & Metallurgy

VFDs and PLCs controlling blast furnace loaders, rolling mills, heavy crane lifts, and cooling fans.

Textile & Spinning Mills

High-speed servo drives, HMI panels, and control cards on spinning frames, carding machines, and weaving looms.

Paper & Packaging

Multi-drive tension control systems, synchronous motors, and PLC controllers on web presses and slitting lines.

Pharmaceutical & Chemical

HMIs, PCBs, and control modules in pill press machines, packaging lanes, centrifuge drives, and mixing vessels.

CNC & Automotive Machining

Precision spindle drives, servo controllers, and logic units in 3-axis and 5-axis CNC machining centers.

Warranty Protection

3-Month Service Warranty

We stand behind our work. All board-level repairs performed by Usha Engineering Services are covered by a comprehensive 6-month warranty on replaced components and workmanship. We use only original, high-grade semiconductor parts sourced from certified global distributors.

Need Help Immediately?

Submit a diagnostics ticket or speak directly with an engineer to get a free estimate and arrange unit pickup.

Frequently Asked Questions

Clear answers regarding repair procedures, pricing, and warranties

What is a static diode test?

It is a multimeter test in diode mode used to check the semiconductor junctions of the input rectifier and output IGBT inverter against the DC bus, detecting short circuits without powering the drive.

Do you offer on-site VFD repair?

For large VFDs (above 75kW), we can provide on-site diagnostics. For standard sizes, units must be sent to our Panchkula lab where we have controlled testing instruments and spare inventories.

How long do VFD capacitors last?

Electrolytic capacitors in VFDs have a lifespan of 5 to 7 years in continuous industrial environments. During refurbishment, we replace them to prevent catastrophic ruptures.

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