EMA recently started a Toshiba T300MVi medium voltage vfd in a coal mine. The following is a service report which should be of interest to anyone purchasing, considering, or operating medium voltage variable frequency drives.
Toshiba has one of the most complete Medium Voltage Variable Frequency Drives ( VFD ) in the market. Some of the MV VFD manufacturers don’t include the medium voltage switchgear and phase shifting input transformer. The fact that the Toshiba T300MVi is all inclusive makes the job of a start up engineer much easier compared to some other brands of medium voltage variable frequency drives.
Recently we had the opportunity to start up a Toshiba T300MVi drive we sold to a customer in West Virginia.
The input phase shifting transformer is very heavy, and has the potential to shift during transportation to the site. The start up procedure includes megging the phase shifting transformer, tightening all power connections, and verifying the mechanical integrity of the MV VFD. The Toshiba 900 HP T300MVi MV VFD weighs about 8300 lbs, and most of that is the input transformer.
We started by isolating the different sections of the Toshiba medium voltage VFD; testing and verifying that each section is electrically and mechanically sound. Megging a 36 pulse transformer is quite time consuming since there are 18 separate wires on the secondary of this transformer, but it’s extremely important to perform this task. In addition to mechanical damage, there is a potential for moisture build up in the transformer. Failing to perform this check could result in substantial damage.
We then checked the diode bridges, followed by the power arm with a multimeter. In this case, all of them checked out fine. Part of this particular start up involved adding an RTD monitor on site. We installed the RTD monitor and interfaced it with a digital input on the Toshiba medium voltage vfd. We verified the customer’s power wiring and supply transformer. All of the measurements were within specifications. At this point, we powered up the MV VFD.
After powering up, we checked to verify that both the primary and redundant cooling fans were working correctly. In this case, we discovered one of the redundant cooling fans was stalled due to shipping damage. We resolved that issue, and then ran the T300MVi VFD in open loop, verified rotation, and noted that all was fine. Since this VFD was running a pulverizer, which requires high starting torque, we change the mode from open loop to closed loop vector. We manually tuned the current loop gains and speed loop gains of the T300MVi and ran product. The customer was very satisfied with the overall improvement on product quality obtained by running the application with the Toshiba T300MVi MV VFD. They can now produce much more precise product than they could do with the motor just running across the line.
EMA is an authorized distributor and repair center for the Toshiba T300MVi medium voltage variable frequency drive ( VFD ). In addition to Toshiba, EMA also routinely performs repair services on the Robicon VFD, the WEG medium voltage VFD, the Allen Bradley medium voltage VFD, and the GE medium voltage VFD.
If you require service, preventive maintenance, or commissioning on a medium voltage VFD, then contact us at 800-848-2504800-848-2504, or just click the contact icon on the top right of this page. IF during normal hours, click the “live support” icon on the right.
We also quote new medium and low voltage vfds and installation.