Managing the effects of VFDs on Motors.

-

Normal motors are designed to operate on a fundamental frequency of 50 Hz. The high switching frequency of the IGBT transistors employed in modern variable frequency drives (VFDs) may degrade the motor insulation system, cause rise in temperature and hence reduce the motor lifetime.



To safeguard the motor from the adverse effects of VFDs, it would be beneficial to consider the following.

Effect of VFD

Options available

Steep voltage pulses that can stress stator winding insulation, might lead to sparking

  • Dual-coated enamel wire for windings
  • Vacuum Pressure Impregnation (VPI) for windings

The common-mode voltage and its associated dv/dt generate bearing currents, which may lead to the breakdown of bearings

Insulated bearing on the NDE side for above 280 frames (> 75 KW) and Hybrid bearing from 160 to 280 frame (15 – 75 KW)

Higher harmonic currents (noise caused by the high switching frequency of a VFD) into the power supply side of the drive and all circuits connected to that supply

Addition of AC reactors at input & output

Radio interference, transient surge & in-rush current caused while operating a motor with VFD

Addition of EMI filters

Increased heating caused due to harmonics while operating a motor with a VFD

  • Motors have to be de-rated for VFD application to account for increased heating.
  • Motors are generally declared @85 % of the Rated KW, Class B temperature rise & one-step reduction in efficiency levels for VFD application

Operating the motor above 50 Hz (fundamental frequency) might result in reduced efficiency due to an increase in eddy current and hysteresis losses

Rise in motor surface temperature due to reduced self-cooling caused by the shaft-mounted cooling fan at lower speeds

For much-reduced speed at constant load, a forced-cooling system is recommended


For any enquiries on AC Motors, please contact 7995080630 or sirusindia@gmail.com.

Comments

Post a Comment

Popular posts from this blog

Information required for supplying the right spares for the AC Motors.

-
Image
Apart from KW, Speed, Frame Size, the following information highlighted in the nameplate would be important to supply the exact spares required. CG - LT Motor ND Series   NG Series APEX Series CG - DC Motors CG - Alternator CG - HT Motor ABB Motor M2BA Series Motor E2BA Series M2BAX Series Motor BBL Motor MA Series Standard Cage Motor Slipring Crane duty motor Crane Duty Motor For any enquiries on Motor spare parts, please contact 7995080633 or  spares@sirus.in .
Read more

Drawing Format for LT, HT & DC Motor Spares

-
Image
If you have imported Motors or Motors without nameplate or if the Motors are very old then also the supply of spare parts can be explored if the drawing is made available after taking the required dimension from the motor. A simple format is given for this purpose and this can be modified to suit your requirement. 1. Cooling Fan 2. Terminal Block 3. Fan Cover 4. Slipring Motor Carbon Brush 5. Brush Holder 6. Slipring Unit 7. DC Motor Carbon Brush 8. DC Motor Blower Assembly For any enquiries on Motor spare parts, please contact 7995080633 or  spares@sirus.in .
Read more

INTRODUCTION

-
Image
Hi. This is Sridhar from Sirus Electronet India P Ltd. This blog is created to exchange and share information on various Electrical Products among the Sirus network members. We will keep posting the latest information on the Products with Photographs wherever it is required. The products include AC Motors, DC Motors. Alternators, Geared Motors, Transformers, Gensets, VFDs, Distribution Boards, etc. You can post your comments for better interaction and understanding.
Read more