Energy Savings

Then why not replace them with 100 kW motors?

At present, I am having 200 KW motors.For 100 KW motor,I have to buy new one.If iI can get clear cost savings calculation, I will work in that direction.Thanks.

How do you change from 220 kW to 200 kW without buying new motors?

<...am having 3 nos.200 KW motors...>

It appears that the Original Poster already has these to hand.

You have to know what the efficiency rating of your equipment is, what is your power factor with present setup? Ideally you should be at about 96% with your present setup...so you may be wasting your time for very little gain...

https://www1.eere.energy.gov/manufacturing/tech_assistance/pdfs/motor_tip_sheet11.pdf

There are strategic matters to consider as well as the energy saving potential:

• The 220 and 200kW motors to hand may well have applications elsewhere within the facility, and may even have a value on the "previously enjoyed equipment" market if presented for divestment.
• Whether a business case for change can be generated depends also upon the utility tariff in force at the facility and any need for some headroom on the utility supply, neither of which can be seen from here.

These factors also have a cash value, which is commercially sensitive and not for sharing here, and therefore need to be worked into the calculations.

Typically, VFD could be wasting about 10% of power it is handling (experts on the forum may confirm). If replacing the motor could result in bypassing the VFD during steady state, for extended hours, that is a saving.

If your system is going to run only at 90kW for many days in a year, then it is worth considering I guess.

Then, you may have power factor issues to worry about as the VFD also helps in maintaining close to unity power factor.

I would say more like 5%, or even less, depending on the input waveform.

However, I think bypassing the VFD is unlikely. The output of a VFD is AC, and the input is DC. AC motors cannot be run on DC, as universal motors do not fit in this thread.

The question here is the efficiency calculations regarding replacement of one motor with another, which cannot be answered here due to lack of information.

I certainly would not be surprised to hear that the high power motor has smaller winding resistance which would lead to lower winding losses.

In this partticular system, are three distinct fans required?

How had would it be to operate using only two motors and fans? Canit be done without degrading performance/safety?

If so, consider removing the VFDs from the motors and instead just run 2 motors and fans at closer to rating, leaving one in standby or as a spare?

This could allow use of the motor fan and vfd other places or sale thereof. Additionally, no power lost running the VFDs.

Hi,

It would be better to understand the load pattern, as with clinker cooling operation, load varies by 50% here and there,

Also, We need to measure Air flow, various temperatures etc at various operations , to arrive at resonable calculation. Hopefully you are already harnessing waste heat recovery.

From the Rules: Do not post phone numbers or email addresses. The Admin will delete all phone numbers and email addresses posted in threads or comments. You can share this information via the forum's internal messaging system.

Polyphase motors this size has an extremely high efficiency(98-99%) at 50-60Hz. VFDs usually operate from 0-400Hz to control the motors speed(rpm). Small motors, 7.5KW or less, a VFD works great, but when you get above that size a motor designed to work at 50/60Hz rating quickly becomes less efficient the farther you get from its design frequency,50/60Hz in the form of heat. Your second question about reducing motor size from 220Kw to 200Kw will be fine if you're using 90Kw, and by using half the motors and VFDs size is probably why nothing has burnt out yet. You asked about savings by switching motors, ideally they should use the same amount of power(90Kw) because it takes that much power to run the fans at their required speed. However this is not including the losses of power in the VFDs, motors, mechanical and electrical resistances, ect. Since this application is fans, it doesn't require large amounts of torque such as pumps, rotational dryers, crushers and any equipment such as this, I suggest a 120Kw or 150h.p. with a mechanical means of slowing down the fans to 1000rpm, such as pulleys and belts or a gearbox. Then and only then, you can use a VFD to fine tune the speed of the fan. But be sure to gear down the motor as close as possible to 50/60Hz, whichever is your countries line frequency. Now everything will be operating at peak efficiency, and with smaller motors your power factor will increase so your peak demand will be lower(I cannot give any amount because I have no information of the amount of power is being consumed), if these 3 motors represent 1/4 or more of power usage it should be noticed immediately in your power bill.