Deterioration Monitoring of DC-Link Capacitors in AC Machine
Drives by Current Injection
Abstract:
This project proposes a novel condition monitoring scheme of dc-link capacitors in PWM
inverter-fed induction machine drives with front-end diode rectifiers, which is based on the
online capacitance estimation scheme. While the motor is operating in the regenerative mode for
the estimation process, a regulated ac component is injected into the stator winding, which
causes a dc link voltage ripple at the same frequency. From the ac components of the dc-link
voltage and current, the capacitance is estimated with a recursive least squares algorithm. With
this method, experimental results have shown that the estimation error of the capacitance is less
than 1%, from which the deterioration condition of the capacitors can be diagnosed reliably.
Existing method:
Reliability of the power electronic converters is one of the most important issues in industrial AC
motor drives where a voltage source inverter (VSI) with a front-end diode rectifier is most
widely used. In the viewpoint of the reliability, the dc-link aluminum electrolytic capacitor in the
motor drive system is more prone to failure than the other components. Due to aging effects, the
capacitor gradually losses its initial characteristic, that is, the capacitance is decreased and the
equivalent series resistance (ESR) is increased.
Proposed method:
In this letter, a novel capacitance estimation scheme of the dc link capacitor for industrial AC
motor drive systems is proposed for monitoring the deterioration condition, where the power
circuit consists of a diode rectifier, dc link, and a PWM inverter. At first, a regulated ac current
component is injected into the q-axis current of the motor. Then, the capacitance is estimated
from the ac voltage and current ripple signals in the dc link, which are processed through the
band pass filter (BPF).
Further Details Contact: A Vinay 9030333433, 08772261612
Email: takeoffstudentprojects@gmail.com | www.takeoffprojects.com
Block diagram:
Block diagram of Induction motor drive system with a front-end diode rectifier.
Advantages:

Productivity Benefits

Energy Savings

Higher Quality

Performance Advantage Over Line Starting
Applications:
 Industrial fans
 Blowers and pumps
 Machine tools
 Household appliances
 Power tools
 Disk drives
Further Details Contact: A Vinay 9030333433, 08772261612
Email: takeoffstudentprojects@gmail.com | www.takeoffprojects.com