motors sharing common load
motors sharing common load
(OP)
Dear All Gurus
How can I drive a huge mill/crusher with two 3 phase induction motors of 90kW each. Four v-belts per motor goes onto a common 8 belt pulley that drives the crusher shaft.
How can I wire the control circuit for the motors starting gear, and what type of starting would be most suitable?
We don`t plan to change the speed of this mill, but struggle to start it with some product in it.
The motors are two identical Teco motors.
How can I drive a huge mill/crusher with two 3 phase induction motors of 90kW each. Four v-belts per motor goes onto a common 8 belt pulley that drives the crusher shaft.
How can I wire the control circuit for the motors starting gear, and what type of starting would be most suitable?
We don`t plan to change the speed of this mill, but struggle to start it with some product in it.
The motors are two identical Teco motors.





RE: motors sharing common load
Post more information about the motors, control gears.
RE: motors sharing common load
Check the KVA/HP code for the motors to ensure that the contactor is large enough. It may need to be larger than 2 x 90 kW.
See here for KVA/HP codes.
ht
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: motors sharing common load
Fred
RE: motors sharing common load
You will want two VFDs with the correct settings and set up to do this right. You need the motors to share the torque load evenly.
Keith Cress
kcress - http://www.flaminsystems.com
RE: motors sharing common load
RE: motors sharing common load
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: motors sharing common load
300HP motors are usually something the local back-hoe operator can lift and manipulate without causing too much collateral damage (as long as it's before lunch
The most common method people use is a large single soft starter and separate OL relays. I have also done a lot of them where I started one motor on the soft starter and after the bypass contactor closed, I closed a 2nd contactor Across the Line, then interlock the infeed conveyor to the 2nd contactor so that you never start feeding product until you have the full HP available. This only works for Impactors however, you cannot usually do that with a Jaw, Pulverizer or Gyratory (Cone) crusher. You will want both motors on-line to accelerate them.
But (as I responded to you in another forum), it is imperative that the motors are identical with identical slip values. So since it appears that is the case, I say go ahead and do it. At 180kW, I would just use one large soft starter and 2 OL relays.
Drives are only necessary if the motors are mismatched, but then the cost becomes prohibitive unless Variable Speed provides a benefit.
Oh, and edison123's sage advice is fantastic!
"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
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RE: motors sharing common load
One set of belts a few thousandths deeper in the grooves will cause that motor to run faster and draw less current than the other motor.
Once V-belts are stretched and broken in it's less of a problem if the mounting is solid.
This application is common in the crusher industry. It's also common to explain to the managers why the electrician can't turn the magic knob to make the motors load share.
Several manufacturers will design and build an assembled starter to do just what you're asking for.