/ News & Press / Video / Start Capacitors & Run Capacitors for Electric Motors - Differences Explained by TEMCo
Start Capacitors & Run Capacitors for Electric Motors - Differences Explained by TEMCo
WEBVTT Kind: captions Language: en
00:00:05.490 so this video I'm gonna dress the 00:00:07.19000:00:07.200 difference between a motor start 00:00:09.47000:00:09.480 capacitor and a motor run capacitor now 00:00:13.77900:00:13.789 there's a couple of fundamental 00:00:15.68000:00:15.690 differences between these two and it has 00:00:17.87000:00:17.880 to do mostly with their construction and 00:00:19.97000:00:19.980 their ability to handle current for 00:00:22.82000:00:22.830 extended periods of time now a motor run 00:00:25.94000:00:25.950 capacitor will be something like this 00:00:28.97000:00:28.980 here and it's engaged in the circuit all 00:00:31.82000:00:31.830 the time these are often used for phase 00:00:34.10000:00:34.110 delay or power factor correction you'll 00:00:37.18900:00:37.199 see these a lot in HVAC units and larger 00:00:39.97900:00:39.989 single-phase motors they're an oil 00:00:44.15000:00:44.160 cooled they're generally in a metal case 00:00:46.04000:00:46.050 now they're filled with oil they tend to 00:00:49.40000:00:49.410 be fairly low capacitance rating so an 00:00:54.17000:00:54.180 example here I've got 15 micro farad's 00:00:57.40000:00:57.410 this one here is 5 micro farad's fairly 00:01:01.16000:01:01.170 small capacitance or values and that's 00:01:04.21900:01:04.229 all that's really necessary often for 00:01:06.20000:01:06.210 the for the run operation on a motor now 00:01:08.99000:01:09.000 a start capacitor on the other hand 00:01:11.06000:01:11.070 these tend to be a bit larger both 00:01:13.85000:01:13.860 physically although always but they're 00:01:17.71900:01:17.729 also larger in capacitance values so for 00:01:21.41000:01:21.420 example this guy here I've got 432 516 00:01:26.60000:01:26.610 micro farad this is something to note on 00:01:28.70000:01:28.710 these capacitors start capacitor to have 00:01:30.53000:01:30.540 a range they're not dead on a lot of the 00:01:33.32000:01:33.330 times that's because the phase shift 00:01:36.20000:01:36.210 produced by running AC current through a 00:01:39.44000:01:39.450 start capacitor isn't as precise or the 00:01:43.13000:01:43.140 precision isn't necessary to get a motor 00:01:45.38000:01:45.390 turning it just needs to be able to 00:01:47.09000:01:47.100 generate a fairly large shift in order 00:01:48.77000:01:48.780 for the motor to start turning 00:01:51.55000:01:51.560 internally on these you have pretty much 00:01:53.42000:01:53.430 the same construction that's two 00:01:54.83000:01:54.840 conductive plates with an insulating 00:01:57.38000:01:57.390 layer in between the two and it's 00:01:59.17900:01:59.189 wrapped too generally in a coil around 00:02:00.64900:02:00.659 and around and around so the two plates 00:02:02.06000:02:02.070 aren't touching each other electrically 00:02:04.58000:02:04.590 anyway and you'll generate a charge on 00:02:07.76000:02:07.770 one and it it transfers to the other in 00:02:12.22900:02:12.239 the case of AC or in DC it'll charge and 00:02:15.73900:02:15.749 hold like a battery now these 00:02:18.18000:02:18.190 Pasteur's motor start and run capacitors 00:02:20.22000:02:20.230 are AC rated capacitors and when you 00:02:22.44000:02:22.450 look on the label of these you'll see 00:02:24.33000:02:24.340 the voltage rating here so for example 00:02:26.97000:02:26.980 this one says here 250 volts ac a 00:02:30.90000:02:30.910 littler one here 220 to 250 volts and on 00:02:34.44000:02:34.450 the run caps here I've got 370 to 440 00:02:38.18000:02:38.190 when you're sizing up capacitors if 00:02:40.77000:02:40.780 you're not replacing one already if 00:02:42.90000:02:42.910 you're just sizing one to start with you 00:02:45.18000:02:45.190 want to make sure that the voltage 00:02:47.31000:02:47.320 rating of your capacitor is about one 00:02:49.26000:02:49.270 and a half times your line rated voltage 00:02:51.06000:02:51.070 this is because the voltage ratings on 00:02:53.13000:02:53.140 these is not RMS but rather peak to peak 00:02:57.78000:02:57.790 voltage on a 240 volt system run 00:03:01.68000:03:01.690 capacitors you'll see 370 to 440 volts 00:03:05.75000:03:05.760 480 volt systems you'll often see 600 00:03:08.76000:03:08.770 volt rated capacitors used on those and 00:03:10.95000:03:10.960 it's just to account for the extra peak 00:03:14.55000:03:14.560 to peak current or I mean voltage levels 00:03:16.71000:03:16.720 that that are present in such a thing 00:03:19.10000:03:19.110 now the other big difference between 00:03:22.26000:03:22.270 these two is duty cycle run motor run 00:03:28.41000:03:28.420 capacitors are a hundred percent duty 00:03:30.24000:03:30.250 cycle they can remain in the circuit 00:03:31.92000:03:31.930 indefinitely charged up so in this case 00:03:34.86000:03:34.870 if I have my I have my box here 240 00:03:37.94900:03:37.959 volts AC and I can connect this right 00:03:41.25000:03:41.260 across this capacitor here like that and 00:03:45.14000:03:45.150 I can switch this on if we measure it 00:03:48.78000:03:48.790 here we can put our voltmeter on AC and 00:03:51.00000:03:51.010 see that there is indeed voltage present 00:03:52.92000:03:52.930 on the terminals right there get 244 00:03:58.44000:03:58.450 point 7 volts and this one's fine too 00:04:01.62000:04:01.630 just leave here like I said one hundred 00:04:02.97000:04:02.980 percent duty cycle you can leave it on 00:04:04.62000:04:04.630 and just in there if you had a motor 00:04:07.91000:04:07.920 running with this or your air 00:04:09.93000:04:09.940 conditioner pump or something along 00:04:12.30000:04:12.310 those lines 00:04:13.59000:04:13.600 this kind of capacitor it just is left 00:04:16.47000:04:16.480 in the circuit 00:04:20.86000:04:20.870 you can use motor run capacitors as 00:04:24.78000:04:24.790 spark capacitors however you cannot use 00:04:28.54000:04:28.550 start capacitors as motor run capacitors 00:04:31.21000:04:31.220 now I'm going to show you why here in 00:04:32.95000:04:32.960 just a second 00:04:33.82000:04:33.830 the disadvantage if you try to use motor 00:04:37.00000:04:37.010 run capacitors that's still live so 00:04:38.68000:04:38.690 don't want to touch it 00:04:39.40000:04:39.410 the disadvantage to using motor run 00:04:41.98000:04:41.990 capacitors as they start up in the 00:04:43.96000:04:43.970 circuit is generally for the startup of 00:04:46.00000:04:46.010 the motor to be able to develop torque 00:04:47.32000:04:47.330 you need a very high capacitance value 00:04:49.51000:04:49.520 to get 150 or 400 micro farad's out of 00:04:53.50000:04:53.510 15 micro farad capacitors you'd need an 00:04:56.20000:04:56.210 entire array of these if you've got the 00:04:57.93900:04:57.949 space for that then that would work out 00:05:00.85000:05:00.860 fine for you now and this is still 00:05:03.93900:05:03.949 energized like I said as you can see 00:05:05.32000:05:05.330 there's there's no effect of having this 00:05:06.82000:05:06.830 in the circuit continuously so let me go 00:05:09.12900:05:09.139 ahead and turn that off and I'm going to 00:05:15.75000:05:15.760 bleed down the capacitor with a resistor 00:05:18.18900:05:18.199 real quick just to make sure that 00:05:19.84000:05:19.850 there's no voltage left on it I don't 00:05:22.90000:05:22.910 want to get shocked there we go 00:05:25.12000:05:25.130 set the meter to DC because when you 00:05:26.83000:05:26.840 turn these capacitors off if you watch 00:05:28.45000:05:28.460 my other video on start caps about 00:05:30.37000:05:30.380 bleeder is that really done resistors 00:05:31.75000:05:31.760 you'll see that when you turn these off 00:05:34.18000:05:34.190 if you turn them off during a period in 00:05:37.99000:05:38.000 the AC waveform other than the zero 00:05:40.81000:05:40.820 crossing these can actually store a DC 00:05:42.67000:05:42.680 voltage up to lethal levels I'm gonna 00:05:46.08900:05:46.099 show you the start capacitor and when we 00:05:48.70000:05:48.710 put a start capacitor into a 00:05:51.64000:05:51.650 current-carrying circuit here it's good 00:05:54.18900:05:54.199 for a couple of seconds now a lot of 00:05:57.49000:05:57.500 times the failure of these will be two - 00:06:00.46000:06:00.470 an overloaded motor or a motor that 00:06:02.86000:06:02.870 doesn't start up all the way or if you 00:06:05.11000:06:05.120 have the centrifugal cutout switch that 00:06:07.18000:06:07.190 doesn't cut out in time and it holds the 00:06:09.27900:06:09.289 capacitor in the circuit too long well 00:06:13.71000:06:13.720 let's show you what happens here safety 00:06:18.18900:06:18.199 first 00:06:21.45000:06:21.460 [Music] 00:06:36.13000:06:36.140 when you leave these things engaged for 00:06:38.29000:06:38.300 more than a couple of seconds here 00:06:40.72000:06:40.730 they don't fare too well now if you do 00:06:43.69000:06:43.700 open up your HVAC unit or your motor and 00:06:46.00000:06:46.010 you find you find something like this 00:06:47.50000:06:47.510 inside go ahead and give a Temko a call 00:06:50.38000:06:50.390 we carry a full line of replacement 00:06:51.97000:06:51.980 capacitors it's area code five one zero 00:06:54.04000:06:54.050 four zero three four zero six one and 00:06:57.52000:06:57.530 we'd be happy to hook you up with some 00:06:58.99000:06:59.000 brand new start or run capacitors for 00:07:00.97000:07:00.980 your application to get you back going 00:07:02.50000:07:02.510 again 00:07:02.89000:07:02.900 also Facebook page is up like us on 00:07:06.16000:07:06.170 there follow us on youtube leave us 00:07:08.05000:07:08.060 comments or suggestions on videos you 00:07:09.85000:07:09.860 guys would like to see I think their 00:07:11.80000:07:11.810 answer your questions or I'll shoot a 00:07:12.97000:07:12.980 video for you with with the response 00:07:14.86000:07:14.870 there tune in next time here and maybe 00:07:18.22000:07:18.230 I'll blow something else up
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