Voltage drop under load transformer 12Vcd 110Vac 60hz - Page 1
Forum section: electronics / repair

author: Solartracker2
author_rank: Contributor
timestamp: February 01, 2024, 05:04:28 pm
content: Hello,First I will say I’m not a electronic person!For my telescope synchronised clock drive plate a have a transformer with a remote control.The problem is that unloaded the output is 100/135Vac (potentialmeter) but when I switched on the clock drive the output voltage drops too 60Vac….I tried it on input at 220Vac and 12Vdc but brought it drops.What is the mostly common fault?

author: inse
author_rank: Super Contributor
timestamp: February 01, 2024, 07:23:23 pm
content: I see the words but fail to understand…What is the supposed output voltage?Is the switch on the primary or secondary side?But without electrical experience I would discourage you from fumbling with 220V AC….

author: Solartracker2
author_rank: Contributor
timestamp: February 01, 2024, 07:58:11 pm
content: Oké sorry.The transformer is a 12Vdc too 110Vac. But when I connect the load the voltage drops from 110V to around 60V. I see no damage at all.So my question is what can cause that voltage drop😬🤔

author: inse
author_rank: Super Contributor
timestamp: February 01, 2024, 08:18:24 pm
content: 12V DC to 110V AC?So its an inverter!Would need a big transistor and a circuit to drive it, but I don’t see any.What i see is two transformers (or one and a inductor) an electrolytic capacitor and maybe a bridge rectifier in the back.Looks more like a power supply to me.Who made this hodgepodge of wires?

author: Solartracker2
author_rank: Contributor
timestamp: February 01, 2024, 08:26:26 pm
content: The fabric 40 years ago!There are two transistors on the front D315

author: inse
author_rank: Super Contributor
timestamp: February 01, 2024, 09:16:24 pm
content: Ok, the bare minimum circuit to drive a transformer…Is the 12V stable at the big electrolytic capacitor?Does anything get hot?Is your load still in spec with the inverter, no mechanical overload…?

author: Solartracker2
author_rank: Contributor
timestamp: February 02, 2024, 02:48:54 pm
content: Hello,I will trying too make it clear.The telescope has 2 110Vac synchronised clock drive motors @60hzThe motors are in parallel connection connected too a inverter/converter.Too controls the speed for the motors there is a controller connected too the inverter/converter.The inverter/converter has two inputs 12Vdc & 220Vac 50hz EUInside it is the 12Vdc direct connected too the transformer by splitting the negative to 2 D315 mosfets.with 1 resistor too on the negative side @ (black-silver-black/green) also is there on the 2 negative input of the transformer bridged by a 10 MDF 50 WV bipolar capacitor.From the 12Vdc there is a connection too the control unit like:Negative—> capacitor(1000uF 63V —> input control unitPositive—> capacitor —> 39 ohms risistor (RSN 2W) —> input control unitOn the control inside there is also a capacitor too the +&- with a value 470uF 16VInside the control unit is this —>And this is the inverter

author: Solartracker2
author_rank: Contributor
timestamp: February 02, 2024, 02:52:56 pm
content: This the control unit.

author: inse
author_rank: Super Contributor
timestamp: February 02, 2024, 07:42:40 pm
content: Ok, for my understanding: you adjust the frequency with the controller to run the synchronous motor at a specific speed.Is the 12V stable and are the transistors getting hot under load?

author: Solartracker2
author_rank: Contributor
timestamp: February 02, 2024, 10:00:27 pm
content: Not hot but little bit “warm”I have a stable 12v 13A

author: inse
author_rank: Super Contributor
timestamp: February 03, 2024, 05:14:11 am
content: Thats 156W and the most of it should go to the motor.As we don’t know neither the specs of the inverter nor the motor, it’s impossible to say whether it’s overloaded or underperforming.Have you verified the mechanism is running smoothly?This will be difficult to debug remotely.

author: Solartracker2
author_rank: Contributor
timestamp: February 03, 2024, 06:51:37 am
content: Thank you for your interest and time!!!!Motors running super smooth for over 40 years old. I think they never ever are used in the past.There are no marks or specs on the transformer unfortunately.On a normal working situation what will be the specs for resistors and capacitors that make a stable output?

author: inse
author_rank: Super Contributor
timestamp: February 03, 2024, 10:15:35 pm
content: There can only be a general answer to a general question, every component has to work according its specifications.Check all resistors and capacitors for their value, check functionality of the transistors.I have no clue how to help you out, sorry

author: Solartracker2
author_rank: Contributor
timestamp: February 04, 2024, 09:11:47 am
content: Is it normale too have a resistor between the 12V - and the transistors B it got very hot 150c!Today I’m measuring the voltage and voltage drop between the capacitor that is connected on the 12V input side and the resistor that is before the control unit and after that resistor because I thought the voltage is dropped/regulated from 12V too 10.xV. I made yesterday a schematic from the control unit and today I finish it with the inverter. Maybe it make more sense to you solving the issue.I’m very happy with all the interest and time you offered to help me!🙏🏻Is it wise too hook up my bench power supply and cut the input feed/line/rail that feeds the control unit too tweaking the input voltage for it so I can measuring the changes on the transformers input and output side?

author: inse
author_rank: Super Contributor
timestamp: February 04, 2024, 09:25:41 pm
content: A strategy to narrow down the failure possibilities is a good starting point.Can you start with a block diagram of the system so we have an overview?

author: Solartracker2
author_rank: Contributor
timestamp: February 05, 2024, 09:31:38 am
content: After measuring and thinking and searching I found out that the point where it must be 5Vdc was 5.x-7.xVdcFurther searching I discovered that there was something wrong how the primary side from the 12Vdv/120Vac must be wrong on the power transistors. With some help from an another person is was the Emitter and Collector wiring was switched 🤦🏼‍♂️.

author: p.larner
author_rank: Frequent Contributor
timestamp: February 05, 2024, 09:57:48 am
content: so is it fixed ok now?.

author: Solartracker2
author_rank: Contributor
timestamp: February 13, 2024, 05:45:55 am
content: I have question about the transistor D315 this should be a NPN type.I’m wondering how this normally needs to be connected because it should need a + on the base and the Emitter goes to the ground and the collector is connected too the negative of the secondary side off the transformer.Is the emitter with or without a resistor connect to the ground? And if need a resistor what would be the value of it?The load on the primary transformer side are 2 in parallel 3W 110Vac 60Hz.On the hand controller there are 2 C1815 and 2 C2001 transistor that are feed from the inverter by a switch on and off potentially meter B10K and for the adjustment for the frequency there is a 50K potential meter that now reads a value of 40K ohm.

author: Jwillis
author_rank: Super Contributor
timestamp: February 14, 2024, 08:39:21 pm
content: Drawing out a schematic of each connection to each component would help determine how the transistors should be connected. Just a labelled box for each component and connector and how they are connected together would be fine.

author: Solartracker2
author_rank: Contributor
timestamp: February 24, 2024, 01:17:00 pm
content: Can you tell me how I can control the maximum power use off the transformer to 3A max on the secondary side (-12v / +12V \ -12V). How can I protect the primary siee of the transformer too spite out 120Vac maximum?