Voltage supply specification and power supplies
Voltage supply specification and power supplies
(OP)
Hi:
We have a a power source of 120 VAC. System requires 115 VAC.
The system have a power supply that is suppose to supplies 24 VDC to a weighing cell. Now it is supplying 30 VDC. The power supplies input is 121 VAC (specification is 115 VAC).
Why we have 30 VDC at the weighing cell? Is that variation OK? Do we have a power supply issues or everything is OK ?
We have a a power source of 120 VAC. System requires 115 VAC.
The system have a power supply that is suppose to supplies 24 VDC to a weighing cell. Now it is supplying 30 VDC. The power supplies input is 121 VAC (specification is 115 VAC).
Why we have 30 VDC at the weighing cell? Is that variation OK? Do we have a power supply issues or everything is OK ?





RE: Voltage supply specification and power supplies
RE: Voltage supply specification and power supplies
Bill
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"Why not the best?"
Jimmy Carter
RE: Voltage supply specification and power supplies
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If we learn from our mistakes I'm getting a great education!
RE: Voltage supply specification and power supplies
If it is a simply double-wave rectifier the system is supplied by a 115/26.5 Vrms [k=4.34] transformer.
Then the output [d.c.] will be Vdc=2*sqrt(2)*Vac/pi() Vdc=24 V.
If Vprime=121 V Vsec=26.5/115*121=27.9 V[rms] and Vdc=25.1 V[d.c.]
In order to get 30 Vdc you need Vsec=33.3 V[rms].
That means the ratio Vprime/Vsec=121/33.3=3.63 [less than 4.34]
Since number of the turns of the secondary winding could not increase no. of primary turns would decrease.
That means there is a short-circuit in the primary winding.
RE: Voltage supply specification and power supplies
If your power supply does not have that feature, maybe you should invest in one. A lot of times people think that any old cheap power supply will do, until they run into this kind of situation.
But check with the instrument supplier first to make sure they don't have a problem with using an SMPS.
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