FAQ# DRV-5WJK95 Published: 07/13/2004
Question:How can the Yaskawa E7 drive start a fan that is windmilling in the opposite direction?
Answer:Methods used by the Yaskawa E7 drive to start into spinning motors.

The Yaskawa E7 drive has excellent speed search capabilities. The E7 can start into a motor that is windmilling in the opposite direction.
  • SPEED ESTIMATION METHOD
For this application, the E7's Speed Estimation mode should be employed. Speed search by speed estimatin will allow the drive to determine the speed and direction of the coasting motor and begin to ramp the motor to a set speed without first having to bring it to a complete stop.

The Speed Estimation method will calculate the speed using measurements of residual motor fields. This version of speed search is bi-directional as motor speed and direction are determined by the E7 drive.
    • To enable Speed Estimation speed search set E7 parameter B3-01 = 1.
NOTE: Auto-tuning must be performed prior to using the Speed Estimation method of speed search.


  • CURRENT DETECTION METHOD
Another E7 speed search method is called "Current Detection".
The Current Detection method of speed search is not bi-directional so it wouldn't be able to find a windmilling fan rotating in the opposite direction. Current Detection method Its function is to searches for the motor from a predetermined frequency while monitoring the drive output current. The E7catches the motor when the drive output current has dropped to a low level. At this point the drives output speed (frequency) has matched the motor speed.
  • To enable Current Detection speed search set E7 parameter B3-01 = 2 or 3.


Other considerations:
Auto-tuning should be performed again if the cable length between the drive and motor is ever changed after the initial Auto-tuning.

For more information, refer to pages 5-11 and 5-12 in the E7 Drive User Manual TM.E7.01

Product Information:

Product Group:Inverters/Drives
Product:E7 Drive
Applications:HVAC
Category:Applications; Parameters; Programming
Part/Model#: CIMR-E7U

Other Information:

Link to related files:TM.E7.01 - E7 Drive User Manual (Installation and User instructions for the E7 drive)
TM.E7.02 - E7 Drive Programming Manual (Describes how to program the E7 Drive parameters)
TM.E7B.01 - E7B Drive Bypass Technical Manual (Installation and User instructions for the E7B Drive Bypass)

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