Diagnosis
 
Helmke is at your disposal in order to carry out diagnostic measures on your drives in our workshops but as well as on your spot.
 
Diagnostic measures in our testing station.
Here, all measurements and tests are available specified according to EN-DIN and VDE regulations.

 
Standard tests for three-phase asynchronous squirrel cage and slipring motors:
  • measurement of DC resistances of individual winding phases in stator winding

  • measurement of DC resistances of individual winding phases in rotor winding

  • insulation resistance check on stator winding

  • insulation resistance check on rotor winding

  • interface clarification of integration in higher process control instrumentation system

  • stator winding check with high-voltage (for new machines 2 x Un + 1,000)

  • rotor winding test with high-voltage (for new machines 2 x Un + 1,000)

  • no-load test: measurement of no-load current and no-load power at rated voltage and rated frequency

  • short-circuit test: measurement of terminal voltage and power at rated current and rated frequency with locked rotor

  • recording of no-load characteristic for evaluation of electro-magnetic dimensioning of the machine as well as determination of no-load losses (separation of friction and iron loss)

  • recording of short-circuit characteristic, measurement of short-circuit loss

  • measurement of rotor standstill voltage with stator under power at rated voltage and rated frequency (ratio check)

  • check of rotating field and terminal marking

  • measurement of shaft voltage on three-phase asynchronous motors

  • evaluation of roller bearings according to SPM method

  • measurement of vibration on A-side and B-side in 3 axes each, at idling at rated voltage and rated frequency

  • functional test of accessories


Special tests:
  • Loss factor measurement (tangent delta) on inserted stator windings

  • loss factor measurement on individual coils

  • determination of polarization index (PI-index)

  • torque measurements at standstill

  • noise ‚ level test

  • core test on laminated core

  • bar breakage test on three-phase squirrel cage motors

  • testing and adjustment of neutral zone

  • testing of tachogenerators and incremental sensors

  • interturn test at 1.2 x Un and 1.2 x fN

  • operational balancing

  • check of air rate and relacity of flow in cooling circuit

  • determination of magnetic center and axial play

  • vibrational analysis

  • true running measurement on collectors and sliprings

  • measurement of brush pressure

  • whirling test (operation of machine at 1.2 times rated speed for a duration of 2 minutes, not possible on 60 Hz motors)
 
 
The following tests will be executed in order to evaluate the condition of your drives:
  • voltage

  • current

  • output

  • temperature

  • speed

  • vibration

  • noise

With the available measurement equipment, these values can be documented and consequences can be taken regarding condition of your motor.

Tests of Coils and Windings

 
When making high-voltage and low-voltage windings, partly being manufactured for applications at converters as well as for traction motors it becomes more and more important that besides the established quality inspections (e.g. determination of the insulation value, PI-measurement and determination of the tangent-delta), tests on windings are executed as well. The tests are necessary for all subsequent considerations and preventive repair works.

Especially shock pulse and partial discharge measurements arose over the past years.

  
 

In the course of the winding manufacture the Helmke test facilities make adequate tests of coil sections as well as of entire stators to ascertain the impulse voltage resistance.
The tests are accomplishable up to 40 kV using digital shock pulse test sources according to EN 60034‑15 or IEE 522. By means of these devices you have a very short time for the voltage
rise of 0.1‑0.2 µs which gives information on electric strength and insulation of the winding.

Special analyzing and diagnostic equipment allow the test even on dc-armatures according to the so‑called segment method.
 

Partial Discharge Measurements

 

Experts increasingly carry out this kind of measurement on running electric motors and generators worldwide. Thereby, it is possible to identify insulation problems early enough to arrange for inspection dates.
Partial discharges are a symptom of the ageing of the winding insulation and there are small electrical sparks in the hollow spaces of the insulation. When the insulation system has faulty places, the risk is high that the winding fails. Regular measurements of the activities of the partial discharge provide relevant information.

Partial discharges may not only occur with high-voltage machines but, because of pulse load, also with inverter-fed low‑voltage machines. A new partial discharge measuring system for motor-integrated inverters allows the measurement at running operation or at winding test with impulse voltage.
source:Link zu Baker Instrumente