If the run capacitor is bad, the motor will start, but fail to deliver rated HP. March 3, 2009. If the loss of one phase occurs before the motor attempts to start, the motor will be in a locked rotor condition, but the amperage will be far less than if all phases were in the circuit. Motor overloaded or jammed. ... (if your machine is single phase). ingersoll rand 60 gal 5 hp 220 single phase runs but after a fill cycle the motor hums and then wont come back on for 30 mins or so. Verify the amp draw of motor versus the nameplate rating. Single phasing presents a difficult problem if its motor starter doesn’t have a single-phase protection feature. Stator is shorted or went to ground (Motor will make a humming noise and the circuit breaker or fuse will trip) Check for leaks through the coils. It is a 240V single phase motor which is a Capacitor start (70uF Cap). 1) The start capacitor is bad. I have read about people using a small single phase motor to get a bigger 3 phase motor going, or using a pull rope wrapped around the motor shaft to pull start the big 3 phase motor. By-passed the starter gear but still no go. The higher the capacitance of the capacitor the more energy it can store. The first is a starting capacitor that has gone bad. This post is about the single phase motor winding resistance testing with complete explanation. Inspect to see that the load is free. Motor capacitors store electrical energy for the motor to use. The capacitor(s) are usually close to the motor in a electrical box on the unit (some motors have the caps mounted on the motor but more often in a HVAC system they are behind a panel). In your case, it's the black plastic one. If leaks are found, the motor must be replaced. The metal one is the run capacitor. I recently had a heavy jack run across the extension cord I made to go to the garage and it tripped the circuit breaker in the house. Blue = Centrifugal switch Brown = main winding black = start winding red = run capacitor 40uf 450v Grey = start capacitor 300uf 250v one electric guy came to me and he told the capacitor UF is too low thats why its giving me smoke, and you have to find the right size of the capacitor, to do it use have to calculate the main winding of the motor Checked capacitor and on a DVM it starts at zero Ohm and ramps up OK, checked starter winding resistance (3.6 Ohm) which seems about right, checked main winding resistance (1.4 Ohm) which again looks good, Motor turns manually with no tightness. The start capacitor provides a quick shot of extra current to help get the motor moving, and (in some motors) tells the motor … If you can't test it, just replace it. If the motor is less than 1/8 HP, it is almost always replaced. When the motor sits and hums instead of starting, the problem could be in a switch or in the starting capacitor. Worst case, after you replace the capacitor, the motor spins freely by hand, and still doesn't start, just hums, you've got a bad start switch. Most problems with single-phase motors involve the centrifugal switch, thermal switch, or capacitor(s). However, if the motor is more than 10 years old and less than 1 HP, the motor is usually replaced. A Grainger # 4CU47 will work. If the problem is in the centrifugal switch, thermal switch, or capacitor, the motor is usually serviced and repaired. From this article you will learn about the single phase induction motor winding resistance, main winding, starting winding. And how to identify start, run and common in the winding. Starting caps provide a phase shift to help the motor start. So if the motor will start but won't keep running, we suspect a bad run winding or bad wiring to the winding. A bad motor capacitor may cause starting problems or could shut off the motor while running. 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