Transformer Specification for 115/230V 50/60Hz mains transformer.
Arcam Part Number L924TX
The transformer is extremely cost sensitive. It is to employ the most cost effective techniques to achieve the specification.
The transformer output voltage will be regulated by a switch mode power supply.
The only essential specification is the fact that it must produce no acoustic noise either internally or by induced eddy currents in steel chassis etc..
All other specifications are negotiable in the interest of allowing cost reduction. Even the use of a frame TX rather than a toroid is negotiable providing it is silent.
1. The transformer MUST be silent when loaded to Po +10% and when supplied from Vin = 270V r.m.s.
General Safety specification.
2.To standards BS415 / EN60065 - Class I / EN60742
3.Transformer to be used in equipment which will be sold worldwide and certified to CE, CB, UL and CSA Standards. All materials etc to be adequate for worldwide safety approvals.
Material Safety Specification
4.Winding Wire to be Grade 2 (130°C rating) to BS
5.Mylar Polyester Insulator Rated to 130°C
Electrical Specification
6.Transformer to have dual 115V primaries to allow parallel operation for 115V input and series operation with 230V input.
7.Transformer is required to provide a mains isolation barrier and provide a single secondary winding.
8.The secondary winding is to be full wave rectified and smoothed as shown in the below diagram.
9.The DC voltage so provided will be followed by a switch mode power supply which will provide a constant power load.
(i.e. the current drawn by the load will increase as the DC output voltage falls- hence the capacitor ripple voltage will be higher at low input voltage)
10.The power drawn by the load has a maximum continuous rating (Po) of 22W.
11.Transformer input voltage range as follows:
115V (85V to 132.5V) windings in parallel
230V (170V to 265V) windings in series
Note. Extended input voltage range 85V to 265V
12. | At minimum input voltage (170V AC) the minimum voltage on the capacitor must be > 22.5V with Po = 22W |
13. | At maximum input voltage and minimum load of 6W the max voltage on output capacitor must be < 63V. |
14. | The secondary voltages and r.m.s currents have been calculated and are tabulated against input voltage. |
The model assumes the transformer regulation is made as poor as possible while meeting spec. | |
The equivalent series resistance of the windings transformed to the secondary is 7ohms under this condition. | |
Rms figures for voltages and currents are true rms figures measured with the specified bridge rectifier, Capacitor | |
and load resistor connected to the transformer secondary. | |
In the case of the load regulation for lowest cost transformer being better than the worst case specification then the | |
TOP VIEW
Secondary Winding Voltage and Current Specs assuming C=1360uF, f= 50Hz for Po = 22W Bridge Rectifier Vf diode = 1.1V per leg = 2.2V Total
Ideal TX assumed with 7Ohm series resistor in secondary to simulate regulation.
AC Supply | Loaded | Capacitor | Capacitor | Capacitor | Load Resistor | Secondary |
Voltage | Secondary | Peak Voltage | Min Voltage | Average | to simulate | Winding r.m.s. |
Pri in Series | Voltage | Vpk | Vmin | Voltage | Load RL | Current |
(V r.m.s.) | (V r.m.s.) | (Volt) | (Volt) | (Volt) | (Ohm) | (A r.m.s.) |
170 | 23.2 | 26.9 | 23.7 | 25.3 | 28 | 1.3 |
230 | 37.3 | 46.0 | 43.7 | 44.8 | 88 | 0.86 |
265 | 44.4 | 55.7 | 53.8 | 54.8 | 130 | 0.75 |
330MM
SECONDARY
PRIMARIES
SCREEN WIRE
GREEN/YELLOW
TX1
Small Toroidal Mains
L924TX
GREY | 1 |
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| 115V | 5 | RED |
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WHITE | 2 |
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PRIMARY BLACK | 3 | 37.3V | SECONDARY |
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| 6 | RED |
| 115V |
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BLUE | 4 |
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| 7 |
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SCREEN WIRE | GREEN/YELLOW |
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transformer voltages shall be modified so that the minimum 22.5V spec is met at 170V input and the output | |
voltages at 230V and 265V input voltage are lower than the specified voltages. | |
15. | Temperature rise to be such that transformer is safe when operated in an enclosure with 50C maximum internal |
temperature. | |
16. | Toroid to be fitted with interwinding screen. |
Mechanical Specification
17.Primary wires
18.Secondary wires
19.Wire type used on the terminations must be such that the wire may be bent with a miniumum bend radius of 10mm through an angle of 90degrees 10times without the wire fracturing. This will allow the wires to be dressed in production without risk of damage to terminations.
20.All wire lengths are +20,
21.Transformer to be marked with part number and issue number.
22.Toroidal transformer will be attached to the chassis by a dished washer and bolt (no potting required).
23.A frame transfomer meeting the above spec will be chassis mounted with flying leads and should have clamp fitted to allow it to be screwed to chassis.
24.Toroidal transformer to be supplied with mounting kit consisting of metal dished washer and 2 neoprene or similar washers.
Voltage on Reservoir Capacitor
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| Vaverage |
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| Vmin |
| 80mm dia max |
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10mS |
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TEST CIRCUIT |
| 40mm max |
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| LEADS EXIT NEAR TOP |
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Vf = 1.1V | +VOUT |
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per diode |
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AC IN |
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+ 1360uF | RL see above table. |
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63V |
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| GND |
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| DRAWING TITLE |
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DV78 TRANSFORMER 115/230V | KAL | Production Release |
| 1.0 | |||
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| 03_E195 |
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ARCAM | Filename: L924TX_1.0.sch | 03_E086 | KAL | Corrected Wire Colours added notes re Clamp | B.0 | ||
Notes: | 03_E042 | KAL | Reduced Power Output Spec, Reduced Load Regulation Spec | A.1 | |||
A & R Cambridge Ltd. |
| 02_E336 | KAL | Prototype Release |
| A.0 | |
| Pembroke Avenue |
| ECO No. | INITIALS | DATE | DESCRIPTION OF CHANGE |
| ISSUE |
| Waterbeach |
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| A3 DRAWING NO. L924TX |
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| Cambridge CB5 9PB | Contact Engineer: Kevin Lamb | Contact Tel: (01223) 203243 | Printed: | Sheet 1 of 1 |
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