Motor Cooling Fans

[Tharon]

I want to cool some large motors (250HP, 3phase). They are TEFC motors, but are hooked up to VFDs, and when they are commanded to turn at slower RPMs, their internal fans don't provide proper cooling.

I was thinking something similar to a CPU fan (but of course larger, and preferably 3 phase). Probably between 1 and 2 foot diamater.

Anyone have any suggestions for manufacturers to look at?

 

[Jimmie_Ohio]

Many motor manufacturers have an accessory kit, field-mountable, to solve this very problem. The cooling fan motor operates independently from the motor being cooled, often with a separate 120VAC single phase supply. It usually bolts on as a replacement to where the internal fan blades are located.

Contact your motor supplier and describe your problem. Ask about a "Constant Velocity Cooling Fan". Specify your motor frame size, HP, etc.

I wouldn't go to Wal-Mart, buy a floor fan and rig something cheap...

 

[504bloke]

Try EMBPAPST

 

[Tharon]

I wouldn't go to Wal-Mart, buy a floor fan and rig something cheap...

I was thinking more along the lines of two nice industrial fans, mounted one either side of the motor to blow air through the fins, helping disipate heat from the body.

I'll look into the manufacturer's replacements. I wonder if they come in 480v 3 phase instead of 120v single.

 

[rsdoran]

Most, if not all, motor manufactures offer separately run fans at motor voltage, for use with inverters.

 

[CharlesM]

We use small 5-20HP motors from Siemens that have extra cooling fans. Its like an extended fan guard. All the ones we use are 120/220 single phase. You could also check with a motor repair shop. They may have something or be alble to make something that would work.

 

[Jimmie_Ohio]

I was thinking more along the lines of two nice industrial fans, mounted one either side of the motor to blow air through the fins, helping disipate heat from the body.

Within a day of installation or on the first hot day in the plant, unless these fans are cemented to the floor, the nearest operator will steal these as quick as they can...

Definitely mount some kind of blower package DIRECTLY to the motor. Then monitor motor temperature in the VFD, if possible, if this fan should fail.

 

[Tharon]

Within a day of installation or on the first hot day in the plant, unless these fans are cemented to the floor, the nearest operator will steal these as quick as they can...

Definitely mount some kind of blower package DIRECTLY to the motor. Then monitor motor temperature in the VFD, if possible, if this fan should fail.

Ya, we weren't gonna just leave them sitting on the floor pointed at the motors. They were going to be fastened in place so they wouldn't move, and so people wouldn't take them.
(Though, it would be difficult because these motors are mounted vertically in a fenced enclosure about 20 feet off the ground).

I'm going to look into the constant velocity cooling fans. They do sound like they'd work much better.

But I am worried about the main body of the motor. With normal TEFC and these CV fans mounted on the ends, how does air circulate around the motor? (I don't know much about physical designs of motors).

 

[Jimmie_Ohio]

In researching a link to illustrate what I meant, I discovered that over a certain motor HP, it appears there is no standard NEMA frame associated with it. I have seen blower packages attach to smaller motors, but not as large as yours (250HP). Manufacturers make their motors a little more "custom" on larger sizes.

What make and model are your motor?

LAST RESORT: If no manufacturer can help, there's another solution. Mount a sheet metal enclosure around the motor. Design a multi-piece "clamshell" design to allow for easy mounting and removal with fan(s) on the inlet end blowing through the motors. Mount an airflow switch at the outlet end to sense and alarm when a fan failure occurs.

 

[Tharon]

These are Siemens 250HP TEFC 449T Frame motors.

I looked into siemens, and they call this CV fan option a "totally enclosed blower cooled" motor. I'll have to see if it's a field attachable option, or something that has to be ordered that way.

 

[Jimmie_Ohio]

These are Siemens 250HP TEFC 449T Frame motors.

I looked into siemens, and they call this CV fan option a "totally enclosed blower cooled" motor. I'll have to see if it's a field attachable option, or something that has to be ordered that way.

Sounds to me like this is EXACTLY what you need...

 

[Lancie1]

For the VFD motor fans that I have seen, the fan motor is controlled by a programmable auxiliary output on the VFD. If the VFD speed is between 0.1 and 60%, fan contactor is energized. If VFD output goes to 0 or above 60%, cooling fan contactor de-energizes.