If the capacitor of the motor of your air compressor is damaged, then the motor takes in an unusual amount of power while starting. Selecting Fuses for Motor Running Protection Based on Motor Actual Full Load Currents 6 Better protection is achieved when fuse ratings are based on motor actual FLA obtained from motor nameplates. The primary fuses will pop when the mains power is turned on, even when no motors nor controls are operational. And it appears the motor starter is just a motor starter. Also, use dual element/time-delay type fuses like Buss FRS-75 or Gould-Shamut TRS-75 which are more current inrush-tolerant. A couple more comments: 70A fuses are a bit light; the national electrical code requires wiring, fuses, etc., to be rated 125% of the load so the fuses should be 75A. 428 Posts . Couldn't see anything obvious in the VFD and nothing read to ground . Motor in rush is usually about 8 x Full load current. These electrical-protection devices prevent damage to equipment by opening a circuit when current flow exceeds the fuse's current rating. Hey guys had a call today for a meat grinder not working. Earlier in the year I posted the following issue=> About once a month a QA200 fuse clears on the utility riser at our plant. 3. UL Class fuses meet size specifications and electrical ratings established as industry standards to ensure that fuses with the same ratings can be interchanged and will perform as expected regardless of brand. The motor of the compressor needs a lot of power to run. The incoming voltage is 490V and the control voltage is 120V. Fuses sized in accordance with Column 5 must be used in conjunction with properly sized motor overload protection such as overload relays or solid state motor controllers (430.32). If the motor is reading fine for ohms, there is no need to check the windings, as the complete circuit has been checked. If the motor has a history of blowing fuses, chances are the motor windings are getting weak under the load. Checked the Line side no short there or the 5 hp motor . A short between the two multiplies the current flowing BACK through the fuse of L1. Column 5 fuse sizing We have a 2000 KVA 12470 -> 480volt transformer. A 1 amp fuse would be able to tolerate momentary spikes above 1 amp without blowing and opening up. The motor then continues running with two phases and can suffer damage. The cause is, for example, blown fuse. It occurs when a circuit is attempting to draw a greater electrical load than it is intended to carry. within the industrial troubleshooting realm today, electrical troubleshooting also requires great computer skills. Industrial Troubleshooting - Electrical . If the voltage is good, go to Step 2. The best way to know for sure is check the voltage at the motor on all three legs. Also called slow-blow midget fuses, they open to disconnect an electrical circuit when exposed to sustained loads and short circuits. Blowing Low Voltage Fuse Breaker Trip | Control Wiring Troubleshooting - I’ve got a 5 amp fuse that keeps popping on a circuit board. So it’s the current running through the fuse that blows it. Check voltage before the starter. Know the VFD is bad so we'll replace it . Copper Conductor 75° C Rating – 30° C Ambient Wire Size Awg No. ... case of motors, a single motor overloaded by just 15% may experience less than 50% of its normal insulation life. The W2U2V2 terminal set is the star side of the 3 phase motor while the U1VIW1 is the Delta side of the motor connected to the supply voltage. 1. Today they went to power up and had no power . There has been no indication as to why it blows. What Types of Fuses are Used for Motor Protection? By Larry Bush. Remove power to the motor and repair any damaged or … A phase failure is an interruption of a single conductor. Automotive, Blade Type & Bolted Type Fuses These types of fuses (also known as spade or plug-in fuses) come in plastic body and two metal caps to fit in the socket.Mostly, they are used in automobiles for wiring and short circuit protection. If your air conditioning system is blowing fuses or causing your home’s electrical system to short out, contact the team at … How do you find and resolve the problem quickly?When that variable frequency drive (VFD) goes down, you're under pressure to get it back online. Check voltage after the starter. If i fit 20 amp fuses, these will not pop, so i know i don't have a short circuit. Motor HP Voltage Typical Motor F.L.A. If not, check supply circuitry, breakers and condition of the motor's power cord. The correct answer requires a specific condition and circumstance. Don't let this pressure make you take even longer to resolve the problem. Low voltage can cause the motor to fail. Related Resources. Check voltage before the secondary fuses. ... A 15 amp fuse that is used to protect a motor circuit would need to account for a temporary increase of electrical power above 15 amps when the motor first turns on. An electrical circuit breaker is a switching device that can be operated automatically or manually for controlling and protecting the electrical power system, and the electrical devices connected to it. Call Air Experts to Fix Your Air Conditioner Issues. A fuse has no way of been influenced directly by the supply voltage, as the supply voltage is not across the fuse. 2. For a 5.5 Kw motor Full load current is about 12 amps at ( 415 volts in Australia) when started Direct on line. Fuse Limiters, Glass Tube (also known as Bosch Fuse) are widely used in automotive industries. Motors should be fused with a time-delay fuse rated 175% of the motor's full load operating amperage, 250% of the full load operating amperage if a circuit breaker is used. I have a 1500VA control transformer fitted with 5 amp primary fuses. However, you might end up needing to rewind or replace it. An overloaded circuit is the most common reason for a circuit breaker tripping. Check voltage after primary fuses. Fuse blowing when on button is pushed. In many cases, the drive components may need to be suitably aligned with the motor to avoid any mishaps of this nature. For the motor, test the stator winding resistance phase-to-phase and phase-to-ground. With individual fuses on each phase, it is just three, single phases (120deg from each other in order), so when L1s sinusoid is swinging negative, L2 is still in the positive. Cant find overloads anywhere. If you find a phase-on-phase short, the motor needs evaluation for a rewind or for replacement. Fuses selected from this column are intended to provide short circuit and ground-fault protection for motor branch circuits. If you find a phase-to-ground short, a motor shop may be able to do an in-place repair for a large motor. I am still popping fuses and reading over 24 volts. This “over-fusing” is commonly seen when fuses keep blowing but it should never be done. For general motor applications, current ratings shall be determined based on the values given in Tables 430.247-250. I don't know if this makes a difference but this is a late 70's machine with all old stuff. This kind of fuse can be easily sized as that of the motor entire load current so that it prevents circuit conditions and short-circuiting for the electrical network. I found all three line fuses blown . And just like ordinary fuses, they are given standard current ratings. If the voltage drops considerably, the wire size is too small. Phase failure. Step 2 Examine the motor's electrical connections and terminals. Actually, the motor requires a lot of power to start and a little less to run. I usually try to use a Motor protection circuit breaker and set for the full load current ,they have an adjustable setting pot on the face and an on/off switch. A component running when stove is plugged in without turning the unit on (most common would be the room air blower, the cartridge heater, or the auger motor). selecting and applying low voltage fuses and medium voltage fuses in electrical systems. troubleshooting in the field - motor testing - motor controller - programmable logic controllers (plc). Small to medium sized motors are mostly stator critical – this means that only the stator can be damaged. ... with single-winding 480 Volt primaries. Mostly, time delay types of fuses are implemented in the applications of motor branch systems. Thus, there are 1 amp, 2 amp, etc. The full-load current is determined using the motor tables found in article 430 as explained in 430.6(A)(1). Additional fuses blowing as soon as the unit is plugged back in. It is rather confusing, and rather deadly. The voltage out of the transformer reads 26.3 volts. The percentages used for general AC motor circuits is 175% for Time Delay Fuses and 250% for Inverse Time Circuit Breakers. The exact voltage that is being supplied to the motor must be checked on a regular basis, including the possibility of loose contacts that can result in tripping or blown fuses. The circuit breaker trips when too much electricity flows through it or when it cannot handle the excess current load. That way you can rule out the starter and all the conductors to the motor. How Fuses Work Overloaded Circuit . When a motor drive goes down, production often grinds to a halt. Locate ... 600 480.00-600.00 521.74-600.00 400.01-480.00 434.79-521.74 If the fan begins to overheat it can often result in a repeated breaker trip until the motor has been serviced. Time-delay, nonindicating midget fuses tolerate temporary inrush currents without opening, which prevents nuisance-blowing from motor and equipment startups. This type of question is full of possibilities for answers since the non-specific nature of the question assumes the one answer fits all. Discussion Starter • #1 • Sep 7, 2012. Removed the motor leads and powered it back up and it blew the fuses . the motor to the wire ends and turn it on. You should replace the motor. Also dont put fuse in parallel or serial Sometimes you can put smaller current rating fuse if e.g. It would not be unusual for a motor to single phase itself to death from a blown fuse, especially if the thermals were not correct. However, if it received above 1 amp for a period of time, it would give way and blow. The motor-specified voltage must be present on all three phases. Table 6 slow-blow fuses. Have a 2000 KVA 12470 - > 480volt transformer – this means only! 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