I have three protection CT's (1 in each phase) in the delta loop of a star-delta starter. The original installation had the CT secondary's (s2)connected together and grounded, and the s1's are connected to a motor protection relay (MPR)
However the protection relay manufacturer's generic data...
Scottyuk
Thanks for the web link, I had an almighty job trying to obtain info on the unit. The factory that the meter is installed in, changed ownership some 5 years ago, and most of the original manufacturers data, manuals, etc were lost or destroyed when the initial owners moved out. Some of...
Tonypdean,
Alehman is correct, DC tries to maintain the arc across the contacts, where AC passes through zero and helps extinction.
One method is to use DC contacts wired in series, which effectively increases the contact gap. Have a look at the information for the 700SP with four contacts in...
BJC,
Your light bulbs - I reckon 0 watts.
Maybe 150 watts instantaneously, until the 60 watt lamp
pops!! I don't really want to calculate how long that will take after the switch is thrown !!
KVKEV
Is there any formulae available, from which you can deduce whether direct online starting of a motor will dip the mains voltage to an unnaceptable level, given the 3 phase fault current level at the motor control center.
i.e If I have a 3 phase fault level of 25kA at 415 volts at the MCC, would...
Twosockets,
Yes I agree entirely, it is normal practice to ground one leg of CT's for metering and protection, and indeed this was how the original installation was configured.
However the manufacturer's handbook for this meter (which was later faxed to me, quotes:
"NB Neither side of any...
Twosockets,
Yes, managed to crack it. The meter manufacturer went out of business some time ago, but luckily managed to contact an ex employee who was kind enough to forward some meter data.
Turns out that the CT's should not have been earthed, and the meter pulsing rate was set up wrongly at...
I have a 2 element kwh meter which is reading only 20% of the expected calculated kwh value. It is connected to a 3.3 kv system via two residually connected ct's, and two vt's with a common secondary ground. I have a power analyser meter on which I have measured the input to the upper and lower...
I have a 2 element kwh meter connected to a delta balanced 3 phase system. It utilises 2 ct's (residually connected to red, and blue phases) and 2 vt's(connected with a common secondary earth). The meter is reading only 20% of the expected calculated kwh.
I suspect that one or both of the ct's...
Can anyone help with the american cable core colouring system. In a single phase system I have black, white and green. Is white the conventional live core ?
In a three phase and earth (delta) system I have red, white, black, (and green). What is the conventional rotation ?
e.g. in U.K it is red...
It is ususally not appropriate to test smpsu and filters at 500 v, because as already advised it can cause damage, and would also fail the test. Other circuits such as the power save mode on some computer monitors use a bridge of 4 x 330 ohm resistors which will return a value of 0.3 to 0.4 Mohm...
