I have an IR pump t30 255 being driven by a 5hp 230 volt single phase motor. The motor is drawing 30-35 amps at max load. The motor is only rated for 26 amps. I decreased thew size of the motor pulley down to 3 1/4". The compresser pump was rebuilt. If i decrease the size of the pump pulley (18"), would the amps drawn by the motor also decrease because the torque would be lower? Thanx for any help.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an alternative browser.
You should upgrade or use an alternative browser.
motor overloaded
- Thread starter batmdcatw
- Start date
Worsedog
Well-known member
No. If you decrease the pump pulley size that would be like increasing the motor pulley.
As a side note are you sure it's a 255, as Ingersoll literature says that is a vacuum pump?
As a side note are you sure it's a 255, as Ingersoll literature says that is a vacuum pump?
Worsedog
Well-known member
The only thing I found in current literature from Ingersoll with 255 in it is a vacuum pump. I looked again, the 255 compressor is not a current production item anymore. Sorry for any confusion.
Anyway it still stands, you don't want to reduce the size of the pump pulley. As far as the pump drawing too much current, so long as the pulleys are of the appropriate size, I can only think of a few things that might cause that.
1. Motor nearing end of life, bad bearings, or run caps bad if it has them.
2. Not so good rebuild.
3. Pressure switch set above the pump/motor combination design limits.
Anyway it still stands, you don't want to reduce the size of the pump pulley. As far as the pump drawing too much current, so long as the pulleys are of the appropriate size, I can only think of a few things that might cause that.
1. Motor nearing end of life, bad bearings, or run caps bad if it has them.
2. Not so good rebuild.
3. Pressure switch set above the pump/motor combination design limits.
I replaced the bearings and the caps are still good. The cut off pressure is set at 130 psi and the cut in pressure 100 psi. I think the only thing i can do without going to a 7.5 hp motor and spending a bundle, is to drop the cut off pressure....dont you think?
PSYKO_Inc
Well-known member
To reduce the number of amps, either make the motor pulley smaller or pump pulley larger. Do it sooner rather than later, the longer it runs at more than its rated current, the more likely it is to burn up. You can figure out the pump rpm by (motor pulley diameter divided by pump pulley diameter) times motor rpm.
MTW
Well-known member
Check you motor nameplate for the service factor (S.F.) Compressor motors usually have a 1.15 SF. 26A x 1.15SF = 29.9A If your running above the SF amperage the motor will be overheating.
Most manufacturers set up their compressors to run over the full load amps near the end of the pumping cycle, into the SF range. This is normally not a problem for cyclic loads where the motor has cooling time between cycles. If you run it hard and continuous (sandblasting) and it stays in the SF range the motor will die early from overheating.
Another thing to look at is the actual voltage while running, versus the nameplate voltage. The lowest running current will be had at the nameplate voltage. Above or below the nameplate voltage value the motor will pull more amperage for a given load. If your feeder or circuit is weak for the load or your utility voltage is high, this will exacerbate your problem.
Voltage can be modified with a buck boost transformer if necessary.
Reducing the size of the motor sheave is the most cost effective means for permanently bringing it down to the nameplate value. It will increase pumping time, but make the motor live longer, especially in hard use scenarios.
The other option is to reduce the pressure setting, lower head pressure equates to less motor load at the peak end of the cycle. The disadvantage here is more start stop cycles, which is hard on 1Φ motors with their capacitor start and centrifigual starting switches.
MTW Ω
Most manufacturers set up their compressors to run over the full load amps near the end of the pumping cycle, into the SF range. This is normally not a problem for cyclic loads where the motor has cooling time between cycles. If you run it hard and continuous (sandblasting) and it stays in the SF range the motor will die early from overheating.
Another thing to look at is the actual voltage while running, versus the nameplate voltage. The lowest running current will be had at the nameplate voltage. Above or below the nameplate voltage value the motor will pull more amperage for a given load. If your feeder or circuit is weak for the load or your utility voltage is high, this will exacerbate your problem.
Voltage can be modified with a buck boost transformer if necessary.
Reducing the size of the motor sheave is the most cost effective means for permanently bringing it down to the nameplate value. It will increase pumping time, but make the motor live longer, especially in hard use scenarios.
The other option is to reduce the pressure setting, lower head pressure equates to less motor load at the peak end of the cycle. The disadvantage here is more start stop cycles, which is hard on 1Φ motors with their capacitor start and centrifigual starting switches.
MTW Ω
TigerDude
Well-known member
Is this a new condition for the motor, or was it just sized wrong?
I think this compressor was meant to be run on a 3 phase motor, not a single phase. I dont think i can go any smaller for the motor pulley ( smallest one from applied industrial technologies), so i am going to lower the cut off pressure down from 130 psi to 110 psi and check the amperage.