motor speed

Hello,

First of all, where are you going to use your motor?

For example,

If you are going to use you motor into an HVAC application, the most practical is to use variable speed drive (VSD)/ variable fruency drive (VFD). For the reason that is you will use two speed motor for this you will have a complicated control circuit with more wires and control devices and this will be limited in to speed variations only. Also, power consumption is much higher as compared to VSD/VFD. While in motors that have VSD/VFD you have flexible system you can vary speed plus power consumption form minimum to maximum speed (sample, motor operates in 5Hz due to less Air conditioning demand this will save a lot more electricity).

That's all for now my friend.

Hope somehow my response helps you a bit.

Regards,

Benn Siman

what's a single coil motor is about? which part of the motor does it relate to?

Our enquirer is referring to a motor whose stator has a single winding,ie three coils,or a motor having an additional electrically separate winding again with three coils but with a different number of poles to give two speeds.

There are lots of combinations of windings some tapped others separate to give a range of speeds and powers from one motor.

Limitations are the actual physical room to wind the multiple windings and the cooling problems of the mass of wire used.

Thank you.

What is referred to as a 'single coil' motor, is just a standard single speed ac motor, while the 'two coil' motor uses two sets of windings that will give two speeds depending on how they are wound. It is like having one set of windings for a 4 pole motor and another for 6 pole.

Regards,

Trevor.

Hi abmar,

Further to what Benn mentions, two speed motors are less common, and if you needed to replace the motor it would be easier to source a 90kW single speed.

Also using a VFD/VSD gives a nice controlled start, with controlled current. Benefits energy management techniques and mechanical loads.

Regards,

Trevor.

I would suggest to use single speed motor with VFD drive as delivery period of two speed is very long also rewinding such motors is a problem.

Quite. There's little a variable frequency drive cannot do these days.

Abmar,

Welcome to CR4. The answers others have made all help with your question. I believe a little more can be added. The best design starts with the application and then chooses the equipment best suited for this application.

If you plan to use the motor where two specific speeds are needed and these match a suitable available motor, then this approach will cost you the least, and operating expenses will be good.

If, however, you really need a more variable speed, then use a more common single speed motor and VSD/VFD. Using a VSD/VFD to change this motor's speed may cost more for initial equipment, but it will save energy costs in the long term. With a VSD/VFD, you need care in choosing a motor which will accept the higher voltages which can occur in many installations (one specifically designed for "inverter duty").

If you use a variable speed transmission, then this is losing you efficiency because the motor is running under a reduced load. Also, a variable speed transmission increases your maintenance costs.

Do well--JMM

VFD's for 90 kW motors ain't cheap, whereas dual-wound motors are, and they're more robust than VFD's of that size.

If u have only two speeds may be yes.Two speed motors normally have a poor efficiency at one of the ratings.In this case since ratings are not wide apart it could be almost the same .But Pl. check that.The one problem is ready availability of replacement.These motors should cost more by 25-30% than say a single rating of 90 KW