Regular Motor or Inverter Duty Motor on a Drive ?

Join Date
Aug 2016
Location
Virginia
Posts
343
Good Morning ,

I have an application that I would like to put a regular fan cooled motor on a drive instead of purchasing a inverter duty motor. This drive will be running at a pre-set speed. What is usually the problem using a regular induction motor instead of a inverter duty motor ?

Thanks so much for your help.
 
We have many regular motors running on VFDs, be sure not to run it to low as the cooling will not be that good. I would say that a inverter duty motor has better insulation in the windings to prevent it from tear down. We have 400V power here and I guess you have 480V and therefor you need even better insulation. It's the reflective waves that will damage the windings.

This is what I have learned and that beeing said we have alot of regular motors running just fine with VFDs, on 400V.
 
Are you just trying to use up a regular motor that you have on inventory? Or, are you trying to save a few bucks on the install?

The regular duty will work, but it will not last as long as an inverter duty will. If you need to order a motor either way, I would go with an inverter duty. The extra money spent up front will pay down the road in less downtime due to premature motor failure, which will of course happen at the worst time possible.
 
Another thing that you could do is to add a load side reactor between the drive and the motor. That will reduce the voltage peaks to the motor somewhat.
 
If you are buying a new motor I recommend buying an inverter duty motor. The price differential is no longer significant, and you will get peace of mind and a bit longer motor life.

For putting an existing motor on a VFD I check these criteria: Class F insulation or better, 1.15 service factor, and drawing less power than nameplate. If these are all true you should be able to apply the VFD without issues.

The most common problem with standard motors is insulation breakdown because of high transient voltages. The second most common problem is overheating - particularly if the load is constant torque or the motor is going to run below 50% speed.
 
Also now part of many (but not all) "Inverter Duty" motors is a system to address bearing currents that can develop as a result of the capacitive coupling between the stator and rotor from the PWM pulses. Either shaft grounding or insulated bearings are used, whereas on regular motors, you would need to add the shaft grounding rings after the fact.
 
Key questions that need answers before a responsible answer can be given.
First, is it 480V service?
Second, how far is the motor (wire feet) from the VFD?
Third, what is the hp?
Fourth, what is the slowest full-torque speed the motor must run at?

Will be happy to give a specific answer when above questions are answered

Buying an MG1 P31 motor doesn't add much cost to a Class F motor anymore but that might not be enough depending on the answers to questions above
 

Similar Topics

Dear all I have PF400 250kW VFD, The operating of VFD is irregular. Please help me to how may i fix it.
Replies
1
Views
1,799
Does TIA Portal support "regular expressions" (regex)? The operator needs to input a unique serial number in this format (see pic). I want to be...
Replies
8
Views
974
Good Morning , I have 2 Frequency Drive panels to build and commission . It is for 2 pump systems . Just wondering , what is the...
Replies
4
Views
1,940
Am I crazy for considering this ? I need to protect a steel tube ø200mm 500 mm long from condensation of moisture on its inside. I need something...
Replies
9
Views
2,978
Good afternoon guys, hope you are doing well. In your experience, which types of VMC are more reliable and last longer from a maintenance...
Replies
0
Views
829
Back
Top Bottom