We have MCB's on the VT's of our latest switchgear and don't anticipate any problems. They are very handy as there are many MCBs in each compartment and fuse wedges can be easily interchanged mixing up the ratings. If there is an upstream LV fuse locked away in a compartment, make sure the...
Agree with all before.
If the customer has a circuit breaker pole in the neutral I'd check it as well.
It's done in Oz with multi-phese supplies on occasions, often when RCDs are fitted to the incoming supply at a main switchboard. As has already been shown here open-circuit (or bad contacts)...
SarahJane, I've dredged the files and come up with performance data on a limited number of motors only (I must have had more of a clean-out than I remembered):
Three data sheets are from a Simpson-Pope Motors (Australia) range tabled in about 1981 but originally put together in 1976. Apologies...
I have some old Crompton (UK) and Simpson (Australia) early motor catalogues boxed up in my garage. Let me know if you want me to look for them I can scan and post. But, they are for 415 Volt squirrel cage 50 Hz machines.
This experience is on a 415 volt 3 phase motor.
We had about 150 metres of 300 sq mm singles Cable feeding a 400 amp FLC motor.
The earth conductor ran neatly alongside the same phase conductor almost the whole length.
The motor suffered a bearing failure after about a year (on Christmas Eve...
magoo2, thanks. We have 500 kV and 220 kV in transmission then 66 kV in local sub-transmission.
I have no info on the transposes (yet) but transmission distances are "long" at about 200 - 250 km depending on how transmission is routed.
I've worked on the outskirts of a major city in Australia and have found at times the line currents of three phase motors installed across a wide area in the same region run out of balance, but only slightly, maybe one to two percent.
When run on a local generator they always come back into...
If it's of any value the metric standard for motor rotation is that RWB connected to L1 L2 L3 on the motor causes it to rotate clockwise looking AT the drive shaft end. Assuming phase rotation is RWB. In thye City of Melbourne 100 years ago the elders decided the phase rotation was to be RBW...
We had a three-phase 415 volt 355 HP 4-pole electric motor driving a compressor. The drive end bearing failed within 1 year due to substantial current flow through it. We tong-tested the phase and earth conductors after the replacing the motor. Phase currents approx 400 Amps, earth current...
Work from:
An internal fault in a switchboard fitted with bus zone prot (HiZ)
-maximum fault current available at the switchboard(amps)
-causes x amps in the CT summated secondary circuit because it's coming in but not going out.
The x amps is flowing through the resistor and the prot relay.
x...
We are installing Siemens slip-recovery drives on three 2.7MW 593 RPM motors driving pumps, presently started by Liquid Starters. Main issue has been the slip rings, not rated for continuous operation (the motors have shorting rings.)
I am NO motor wiz but is it feasible to get a rotor built for DC excitation? Then control of the DC to the rotor may porovide th econtrol you need (meeting torgue and PF control.
I'd recruit an expert.
If you do the VSD 60 Hz to 50 Hz job, get the VSD supplier to assist with its settings, V/f curve especially. Crudely, if the VSD outputs 380 volts at 60 Hz, it will output less volts at 50 Hz. This could lead to motor overloading if full HP are reuired. You will need to "tailor" the V/f...
Gents,
We had an interesting experience with an induction generator in the 1980s in Victoria Australia. A 12 MVA (approx) 22 kV 50 Hz unit was installed at the end of a 30 km overhead line. When put on line 1st time the 22 kV line volts fell to 50% at a country town half way along it. That's...
