Torque Limit
Torque Limit
(OP)
Hi,
We had a breakage on a shaft and we are now having an issue with our insurance company. The SWL of the shaft was 2400 kNm with a safety margin of 2. The load is a stone crusher which is operated through a gearbox and the output shaft drives the load. The nominal torque on the low speed side of the gearbox is 2200 kNm and the torque limit on the VSD was set to 2000 k Nm. The VSD was set to operate on a constant torque curve and the mode of operation was the direct torque control one. The insurance company is claiming that the VSD could have given 250-300 % of the maximum torque during the starting phase of the drive, particularly during seizing period, and this was the cause of the breakage. They have difficulties to accept that the torque limit set on the drive would prevent the output torque to raise above 2000 k Nm. How accurate is the torque accuracy on a VSD ? I know that DTC technology claims the best accuracy amongst open loop drives.
Thanks.
Guardiano
We had a breakage on a shaft and we are now having an issue with our insurance company. The SWL of the shaft was 2400 kNm with a safety margin of 2. The load is a stone crusher which is operated through a gearbox and the output shaft drives the load. The nominal torque on the low speed side of the gearbox is 2200 kNm and the torque limit on the VSD was set to 2000 k Nm. The VSD was set to operate on a constant torque curve and the mode of operation was the direct torque control one. The insurance company is claiming that the VSD could have given 250-300 % of the maximum torque during the starting phase of the drive, particularly during seizing period, and this was the cause of the breakage. They have difficulties to accept that the torque limit set on the drive would prevent the output torque to raise above 2000 k Nm. How accurate is the torque accuracy on a VSD ? I know that DTC technology claims the best accuracy amongst open loop drives.
Thanks.
Guardiano





RE: Torque Limit
Also in a lot of cases we program a delay on tripping to allow for starting. Did you check the programming?
"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: Torque Limit
"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: Torque Limit
Any chance of a picture of the broken shaft?
Just looking at the failed shaft can tell us a lot about the failure, also how long as the motor been in service?
desertfox
RE: Torque Limit
Thanks.
Guardiano