Dust collector motor

[David Kumm]

How hot should a motor get? My 3 phase 5hp baldor dust collector motor gets hot to the touch after it is on for an hour. Not too hot to touch but too hot to wrap my hands around and hold for very long. I run it off a vfd and a little over 60hz. This is with gates open and about 11 amp draw. Dave

[Philip Rodriquez]

Dave, respectfully, motors get hot after an hour.

[David Kumm]

Phillip, Thanks, I thought I was fine but as a one man hobby type I almost never have any motors on very long so i had no frame of reference. My trouble is usually wearing out the on off switches. Dave

[Ole Anderson]

Check the motor nameplate, it might list the allowable temperature rise under full load, usually 40 or 60 degrees.

[Angie Orfanedes]

That would be celsius (centigrade)...if you can barely hold your hand on it, it is usually about 140 degrees F - which is okay for most motors.

Angie

[Doug Palmer]

As a rule of thumb, you should be able to place the palm of your hand on the motor and leave it there for at least 2-3 seconds. That is not to say it might be a little uncomfortable. If you are having to jerk your hand off immediately, you may be on the verge of burning up your motor. FYI a true 5 hp motor will pull significantly more than 11 amps. You can always put an external fan blowing on your motor to keep it cool, but from the sound of your post, you are fine.

[David Kumm]

Thanks all. The heat is within your examples. Yes the motor is rated for 12fla. I run it off a vfd at 63 hz to give it a little boost. With all gates open it tops out at 11.5 which tells me my input or output pipes or filters are a tad restrictive for the motor and fan. Watching the amp draw as the gates are opened and closed is a pretty good indication of how the system is balanced. My motor is up in the attic so I only get up there to check it when I get ambitious.

[Chip Lindley]

As a rule of thumb, you should be able to place the palm of your hand on the motor and leave it there for at least 2-3 seconds. That is not to say it might be a little uncomfortable. If you are having to jerk your hand off immediately, you may be on the verge of burning up your motor. FYI a true 5 hp motor will pull significantly more than 11 amps.

The OP has a 5hp Baldor 3-phase motor that probably draws around 12A on each leg--not to be confused with a 5hp single-phase motor which may draw from 20A-25A on two legs.

Also FYI, TEFC-type motors are by definition, totally enclosed with an external cooling fan that blows cooling air over the motor's case. These are built to run hotter than open, drip-proof motors which allow air to circulate through the windings and rotor.

Since the DC is probably the hardest working machine in the shop, it is also probably the hottest. Motor heat is directly related to amperage draw. Your starter's overload should trip on a 3-phase motor when it's limit is reached. If your DC is a commercial 3-ph 5hp unit with OEM motor, it is built "to take it"!

[Doug Palmer]

The OP has a 5hp Baldor 3-phase motor that probably draws around 12A on each leg--not to be confused with a 5hp single-phase motor which may draw from 20A-25A on two legs.

Also FYI, TEFC-type motors are by definition, totally enclosed with an external cooling fan that blows cooling air over the motor's case. These are built to run hotter than open, drip-proof motors which allow air to circulate through the windings and rotor.

Since the DC is probably the hardest working machine in the shop, it is also probably the hottest. Motor heat is directly related to amperage draw. Your starter's overload should trip on a 3-phase motor when it's limit is reached. If your DC is a commercial 3-ph 5hp unit with OEM motor, it is built "to take it"!
Good catch on the 3 phase, I didn't notice it. A 5 hp motor at 230 v 3 phase typically pulls 15.2 amps per leg. So 11 amps is not significantly low as I previously stated. Hand check is only rule of thumb and is a good guideline. It always a good idea to check your equipment. I have no idea which frame is on the motor since he didn't state it, but it really doesn't matter as far as motor temperature. Heat causes the insulation to breakdown. In the case of a motor the insulation is varnish. Get it too hot it gets soft, get hotter it may melt and the short motor windings. A TEFC motor has a fan blade attached to the outboard shaft. It does not allow the motor to run hotter, it prevents the motor from getting as hot because it is moving air across the fins which work as a heat exchanger there by allowing the motor to work harder without overheating. Otherwise I agree with your post.