Not to be argumentative but to make sure I am on the right track - my understanding is that back EMF is a voltage, albeit an induced voltage. If that is true, then would that not contradict your statement "An induction machine, operating as a generator, only generates power, it does not...
This has been my assessment as well. Meanwhile, my colleague seems concerned that current induced in the de-energized motor windings due to the rotor being 'pulled along' at 120 rpm needs to be dissipated somehow.
Also to clarify my verbiage regarding the power supply, the motor would be...
In your anecdotal example, are the 4kW and 8kW motors individually clutched in/out of engagement with the load, or is one motor always being pulled along de-energized while the other motor is in operation?
Allow me to clarify - The motor power leads are connected to the motor starter, but the motor starter (contact) is open such that no electrical power is available to the motor while it is being 'pulled along' at 120 rpm.
Good Afternoon all,
I am working on a drivetrain application where we will have an 11kW, 400V/3-ph/50Hz, 4-pole motor that is 'dragged along' at 120 rpm for a short time period, not to exceed 20 seconds, at initial startup of the system. The motor would be connected to its 400V power supply...
@EdStainless - The turbine blade is 2.25" wide, approx. 1.40" long, and approx. 0.44" max section thickness (at the entering end of the blade). Polishing the blades is an interesting idea, and something we could accomplish without too much additional work. Do you have any detailed...
@Heaviside1925 - Thank you for your reply! I am very confident that the root cause of this material failure is the customer's insistence on operating our torque converter in its reduced pressure mode for prolonged periods, whereas it was intended to operate in the reduced pressure mode for...
Hello All -
I am chasing an issue with a torque converter that we use in our mechanical package and I could use some outside advice. The blades in the turbine wheel are exhibiting advanced erosion due to cavitation in the working fluid (ISO VG 32 light turbine oil). The root cause of the...
Thanks all for the advice. Now we have some more ammunition to go back to the customer and hopefully get to the bottom of this. I will follow back if we get any meaningful information from them.
Fortunately (or unfortunately, depending how you look at it), our scope of supply for electrical devices is limited to the motor. The Customer provides the motor starter and any other electrical equipment needed to operate and monitor the motor. So in short, I cannot supply the make and model...
@ waross - Thank you for the insight. I will ask the Customer to confirm how they are measuring the current.
The 3kW motor is the driver for our turning gear assembly, and the turning gear is driving a steam turbine + compressor train. Assuming no mechanical issues with the steam turbine or...
@ Parchie - I should have clarified that this is a directly coupled motor, not a belt drive. Our design calculation shows that the load torque is less than the available torque from the motor. The Customer has concluded that the actual load torque is higher than calculated and exceeding the...
Thanks for the additional feedback. Getting information from this customer is very difficult, but we are trying to get more details.
The story they gave us is this: the Customer used the 40A locked rotor current from the motor data sheet to set the current limit on their motor starter. When...
@ itsmoked: it also crossed my mind that the motor might be intended for wye connection but was wired delta by the customer. However, the data sheet for the motor states that it is intended for a delta connection. But running with the idea that the motor data sheet is incorrect: if I apply...
@ waross: Is there any condition where a motor can physically pull higher amps than its rated Locked Rotor Current (or Starting Current as they say in IEC world). What the Customer is reporting is that the motor is drawing 70 Amps at startup, while the data sheet for the motor shows that the...
