Method for diagnosing a frequency converter

Patent metadata

Field	Value
Publication number	US-9431936-B2
Application number	US-201514596258-A
Country	US
Kind code	B2
Filing date	Jan 14, 2015
Priority date	Jan 28, 2014
Publication date	Aug 30, 2016
Grant date	Aug 30, 2016

Abstract

A method for diagnosing a frequency converter is used for a frequency converter having a positive and negative DC link voltage which is applied via bridges of switching elements in an alternating sequence to phases of a motor. Pulse width modulation (PWM) signals drive the switching elements for a respective one of the phases and current sensors capture phase currents. In a step a), PWM signals are applied as test patterns to the switching elements. In a step b), sensor signals of the current current sensors are picked up. In a step c), the sensor signals are evaluated by ascertaining a presence of the DC link voltage upon a displacement current being recognized in the sensor signals.

First claim

What is claimed is:

1. A method for diagnosing a frequency converter, the frequency converter having a positive and negative DC link voltage which is applied via bridges of switching elements in an alternating sequence to phases of a motor, wherein pulse width modulation (PWM) signals drive the switching elements for a respective one of the phases, and wherein current sensors capture phase currents, the method comprising:
a) applying PWM signals as test patterns to the switching elements;
b) picking up sensor signals of the current sensors; and
c) ascertaining a presence of the DC link voltage upon a displacement current being recognized in the sensor signals at each of the flanks of the PWM signals applied as the test patterns, the displacement current being recognized by detecting discrete current spikes occurring in the sensor signals and determining whether each respective one of the current spikes temporally coincides with each respective one of the flanks of the test patterns.

2. The method as recited in claim 1 , wherein, in step a), the test pattern has a pulse duty factor of 50%.

3. The method as recited in claim 1 , wherein, in step a), the test pattern is output synchronously for all of the phases.

4. The method as recited in claim 1 , wherein the current spikes are detected by comparing the sensor signals to limit values.

5. The method as recited in claim 1 , wherein, in step b), the sensor signals are picked up for at least two phases of the motor, the method further comprising:
comparing an amplitude of the displacement currents in the sensor signals for the at least two phases of the motor so as to ascertain whether the phases are connected to the motor or not; and
identifying a first one of the at least two phases that is not connected based on a second one of the at least two phases having a higher displacement current than the first one of the at least two phases.

Assignees

• Heidenhain Gmbh Dr Johannes

Inventors

• Ritz Franz
• Huber Norbert

Classifications

• G01R19/16547

  voltage or current in AC supplies (switching for protection H02H; circuits for emergency power supply H02J9/00) · CPC title

• H02M1/32

  Means for protecting converters other than automatic disconnection · CPC title

• G01R31/42 Primary

  AC power supplies · CPC title

• H02M7/48

  using discharge tubes with control electrode or semiconductor devices with control electrode · CPC title

• H02M7/5387

  in a bridge configuration · CPC title