Step Down Transformer Recommendation for AVR

[analogadikt]

I use several vintage American amps that are 117 volt/60 Hz as per the back plate. I have 1.5 KVA step down that delivers 120V at 50Hz. I face no problems

There are many turntables with A/C motors that can be selected to run at either 110/120 or 220/240 volts. To give give the correct and same platter speed at either 59 or 60 Hz, only the pulley of correct diameter needs to be fitted. The motor has no heating or whatever problem as long as the voltage supplied matches the selected configuration on the motor.

The drill motor overheating problem is most likely due to the step down delivering inadequate current.

The AV receiver circuit runs on DC. There is a rectifier after the transformer secondary that converts the A/C output from the trafo secondary to D/C. The frequency of the A/C supply has no effect on the circuitry.

A previous discussion

Step down transformer for stereo amplifier

Recently purchased a pioneer amplifier sa8900 rated at 110 watts (Japanese market ) obviously from the used market . After buying I read a thread in Hifivision for hum generated from step down transformers . Three questions : 1. Brand to be used for the amplifier in India 2. What KVA rating of...

www.hifivision.com

Regards,

 

[Subbu68]

There are many turntables with A/C motors that can be selected to run at either 110/120 or 220/240 volts. To give give the correct and same platter speed at either 59 or 60 Hz, only the pulley of correct diameter needs to be fitted. The motor has no heating or whatever problem as long as the voltage supplied matches the selected configuration on the motor.

There you have..

The turntable is multi-voltage compatible as per your post - you switch to 220/240V and the transformer inside is designed to work on 50Hz too - larger size. So too your motor. Larger size than a regular 60Hz rated motor.

the motor speed in AC motors (it is not A/C that is acronym for air conditioner) is governed by frequency. When you switched from 60Hz to 50Hz you changed the pulley of correct diameter to adjust the speed. That's how you compensated for lower motor speed at 50Hz.

If rated to operate only on 60Hz the magnetizing current is less than one designed to operate at 50Hz and the manufacturer will not oversize the core of transformers and motors to make them compatible to operate at 50Hz. It is core material and copper used for winding that is saved and if they make say 5000 units over it's life time, overall cost will be less due to this saving.

The drill motor overheating problem is most likely due to the step down delivering inadequate current.

Drill motor is overheating exactly due to this issue of smaller size core. It also runs slower which means lower torque and overheating due to higher magnetizing current and the torque not able to meet the load.

I use several vintage American amps that are 117 volt/60 Hz as per the back plate. I have 1.5 KVA step down that delivers 120V at 50Hz. I face no problems

The AV receiver circuit runs on DC. There is a rectifier after the transformer secondary that converts the A/C output from the trafo secondary to D/C. The frequency of the A/C supply has no effect on the circuitry.

A previous discussion

Step down transformer for stereo amplifier

Recently purchased a pioneer amplifier sa8900 rated at 110 watts (Japanese market ) obviously from the used market . After buying I read a thread in Hifivision for hum generated from step down transformers . Three questions : 1. Brand to be used for the amplifier in India 2. What KVA rating of...

www.hifivision.com

Regards,

The amps maybe having larger than required size transformers so you'd experience no heating. Vintage designs were overdesigned to last long but not the modern ones.

Yes AV receivers run on DC. No doubt but the transformer at the input is the one that could get overheated due to frequency change.

 

[analogadikt]

There you have..

1)
The turntable is multi-voltage compatible as per your post - you switch to 220/240V and the transformer inside is designed to work on 50Hz too - larger size. So too your motor. Larger size than a regular 60Hz rated motor.

2)the motor speed in AC motors (it is not A/C that is acronym for air conditioner) is governed by frequency. When you switched from 60Hz to 50Hz you changed the pulley of correct diameter to adjust the speed. That's how you compensated for lower motor speed at 50Hz.

If rated to operate only on 60Hz the magnetizing current is less than one designed to operate at 50Hz and the manufacturer will not oversize the core of transformers and motors to make them compatible to operate at 50Hz. It is core material and copper used for winding that is saved and if they make say 5000 units over it's life time, overall cost will be less due to this saving.


Drill motor is overheating exactly due to this issue of smaller size core. It also runs slower which means lower torque and overheating due to higher magnetizing current and the torque not able to meet the load.



The amps maybe having larger than required size transformers so you'd experience no heating. Vintage designs were overdesigned to last long but not the modern ones.

3)
Yes AV receivers run on DC. No doubt but the transformer at the input is the one that could get overheated due to frequency change.

1)Idler drive turntables have AC shaded pole induction motors. There is no transformer. The coils are connected in series or parallel depending upon the supply voltage.

2)
I know motor speed is governed by the supply frequency. I have installed frequency based speed controller for turntables and shall be doing a few more. I am also aware of the relationship between pulley diameter and speed. I own dozens of turntables that I service myself and also do custom builds.

3)
After installing the step down, the transformer temprature can be monitored with thermometer and a cooling fan can be installed if the need is felt. Rewinding the existing transformer shall void the warranty and without a service manual it won't be possible to to work out the secondary voltages and current. In fact , I doubt that this data is available in the service manual. It shall just have a replacement part number.

If I land up with such an equipment and notice abnormal temprature in transformer after operating through a step down (I use a digital industrial thermometer) then I shall get 60Hz pure sine wave inverter like this.

GTSUN 1000W DC 24V AC 110V 60Hz Pure Sine Wave Power Inverter USB.Fuse Built Out. Easily Changed. Remote Control : Amazon.in: Electronics

GTSUN 1000W DC 24V AC 110V 60Hz Pure Sine Wave Power Inverter USB.Fuse Built Out. Easily Changed. Remote Control : Amazon.in: Electronics

www.amazon.in

It can be connected to the regular inverter battery in the home only to get the correct output voltage and frequency. Chargeing the battery shall be as usual by the India spec inverter. Switches shall have to be devised to ensure isolation.



Regards,

 

[Subbu68]

1)Idler drive turntables have AC shaded pole induction motors. There is no transformer. The coils are connected in series or parallel depending upon the supply voltage.

2)
I know motor speed is governed by the supply frequency. I have installed frequency based speed controller for turntables and shall be doing a few more. I am also aware of the relationship between pulley diameter and speed. I own dozens of turntables that I service myself and also do custom builds.

3)
After installing the step down, the transformer temprature can be monitored with thermometer and a cooling fan can be installed if the need is felt. Rewinding the existing transformer shall void the warranty and without a service manual it won't be possible to to work out the secondary voltages and current. In fact , I doubt that this data is available in the service manual. It shall just have a replacement part number.

If I land up with such an equipment and notice abnormal temprature in transformer after operating through a step down (I use a digital industrial thermometer) then I shall get 60Hz pure sine wave inverter like this.

GTSUN 1000W DC 24V AC 110V 60Hz Pure Sine Wave Power Inverter USB.Fuse Built Out. Easily Changed. Remote Control : Amazon.in: Electronics

GTSUN 1000W DC 24V AC 110V 60Hz Pure Sine Wave Power Inverter USB.Fuse Built Out. Easily Changed. Remote Control : Amazon.in: Electronics

www.amazon.in

It can be connected to the regular inverter battery in the home only to get the correct output voltage and frequency. Chargeing the battery shall be as usual by the India spec inverter. Switches shall have to be devised to ensure isolation.



Regards,

The basic discussion was to make those who are not aware that simply getting a 240/110V step down transformer may not work for all cases. The frequency in India and most of the world is 50Hz and there is a risk involved in getting 60Hz rated equipment and use with a 50Hz supply.

All induction motors are basically transformers. All have a magnetic circuit that draws a magnetizing current to set up the magnetic field and it cannot work without it. Shaded pole motors are used to control the speed without using an external voltage controller or a series resistor to drop the voltage and associated power loss. Instead it is a tapped winding on the stator pole that works like an autotransformer. Switch the tap to change the effective voltage applied to the stator pole and control the speed.

I don't own any TTs (don't want to) but since you said they use shaded pole induction motors that may be the way the speed is switched between different speed vinyl. You know it better since you service TTs.

There are more than temperature rise aspect if devices designed for 60Hz are used at 50Hz. The core (motor or transformer) is sized for a certain flux. The turns on the stator of motors or primary of transformer are chosen to have a certain Xm and Rm (magnetic impedances). This would mean a lower size core and lower impedance of the coils but increased current and overheating, lesser short circuit rating.

One cannot rewind the existing transformer or motor as the core is not designed for that flux at 50Hz.

Safest bet in my humble opinion would be to get a replacement part rated for 240V, 50Hz. Most manufacturer or agents in India may oblige your request if you bear the cost.

No electronics can generate pure sinewave. They generate also harmonics that can vary with the filter. That is why we have certain regulations and standards to curb the menace of power system harmonics.

 

[mbhangui]

The basic discussion was to make those who are not aware that simply getting a 240/110V step down transformer may not work for all cases. The frequency in India and most of the world is 50Hz and there is a risk involved in getting 60Hz rated equipment and use with a 50Hz supply.

All induction motors are basically transformers. All have a magnetic circuit that draws a magnetizing current to set up the magnetic field and it cannot work without it. Shaded pole motors are used to control the speed without using an external voltage controller or a series resistor to drop the voltage and associated power loss. Instead it is a tapped winding on the stator pole that works like an autotransformer. Switch the tap to change the effective voltage applied to the stator pole and control the speed.

I don't own any TTs (don't want to) but since you said they use shaded pole induction motors that may be the way the speed is switched between different speed vinyl. You know it better since you service TTs.

There are more than temperature rise aspect if devices designed for 60Hz are used at 50Hz. The core (motor or transformer) is sized for a certain flux. The turns on the stator of motors or primary of transformer are chosen to have a certain Xm and Rm (magnetic impedances). This would mean a lower size core and lower impedance of the coils but increased current and overheating, lesser short circuit rating.

One cannot rewind the existing transformer or motor as the core is not designed for that flux at 50Hz.

Safest bet in my humble opinion would be to get a replacement part rated for 240V, 50Hz. Most manufacturer or agents in India may oblige your request if you bear the cost.

No electronics can generate pure sinewave. They generate also harmonics that can vary with the filter. That is why we have certain regulations and standards to curb the menace of power system harmonics. View attachment 71878

Nice map. Probably needs to be updated. India is shown as 230v. But the shade now needs to be darker indicating 240v which has been done around 2 years back for economic reasons and which puts us in the same league as Afghanistan and two African countries.

 

[Subbu68]

Nice map. Probably needs to be updated. India is shown as 230v. But the shade now needs to be darker indicating 240v which has been done around 2 years back for economic reasons and which puts us in the same league as Afghanistan and two African countries.

Yes, still many websites write that India is 230V, 50Hz. Same case with UAE

 

[analogadikt]

1)
Safest bet in my humble opinion would be to get a replacement part rated for 240V, 50Hz. Most manufacturer or agents in India may oblige your request if you bear the cost.

2)
No electronics can generate pure sinewave. They generate also harmonics that can vary with the filter. That is why we have certain regulations and standards to curb the menace of power system harmonics. View attachment 71878

1)
The equipment in question is US market model only. There is a near identical model with a bit different model number for the European market. From what I have seen about the dealers, service agents (if any) of these brands here, they won't be of much help to check if the transformer of that European model shall suit this one, if at all they progress on this, the cost shall be exorbitant.

2)
The harmonics that you mention are generated by SMPS, thyristor/ triac based power supplies, controllers. They pollute the power supply, making it dirty. The cheap inverters, sold mostly in mofussil areas are also problematic. They have square wave traces in the output.
A regenerative type power supply is based on an oscillator, usually crystal based. The frequency generated by this is amplified by an amplifier circuit that is very similar to an audio amp. A step-up transformer is usually employed at the final output. This is a very clean and pure supply, you can check this on an oscilloscope.
Some years ago, MSEB fined some IT companies in Pune for pushing dirt in the supply. The problem can be easily seen and understood in my house. When certain equipment is switched on in the neighborhood, my stereo system develops a background hum. This disappears the instant I switch to the back up supply. The back up is pure sine wave based with 1.1 VA capacity. I can run my system on it for several hours.

Forum members are welcome to my place to check this and enjoy pure analog stereo.

IMHO, my suggestion of using the 60Hz pure sine wave inverter is safe and technically correct.

I am leaving this discussion. All the best to the OP for getting his problem sorted and being able to enjoy his AVR.

Regards,