Maximum voltage for IEC 60601?

L

liutianyifly

#1
Hi, all

I am designing a medical device which should be attached to human skin (somehow like a hearing aid), I have two questions about it.


1, Does it belong to "hand-held" ME equipment?
the term "hand-held" referring to electrical equipment intended to be supported by the hand during normal use. ----3.37


2, I am using a high voltage regulator(DC/DC) inside (around 180 volts). I want to make sure if it is illegal?

For ME equipment intended to be connected to supply MAINS, the following rated voltages shall not be exceeded:
- 250 V for hand-held ME equipment (4.10.2)


Thanks in advance
 
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Peter Selvey

Staff member
Super Moderator
#2
1. Seems to be not hand held. I guess the concern might be that hand held equipment must only have voltages under 32Vac/60Vdc. But actually this only applies to hand held control devices. For other hand held devices (e.g. an ultrasound probe) it is OK to have higher voltages inside.

2. No problem as long as everything the HV circuit (200V) is properly insulated to prevent shock, or unintended paths in case the voltage is being intentionally applied to the patient (e.g. simulator).
 

Roland chung

Trusted Information Resource
#3
But actually this only applies to hand held control devices. For other hand held devices (e.g. an ultrasound probe) it is OK to have higher voltages inside.
The standard does not give a definition of hand-held control device. Hand-held control device may mean hand-held switches. How about the hand-held accessories of high frequency surgical generator?
 
L

liutianyifly

#4
Hi, Peter, many thanks.

if it is not belong to hand-held then what kind of device it should belong to ?
for example what is ultrasound probe belong to ?
what is the highest voltage can be used inside this probe? 500 volts?
in IEC60601, 4.10.2 it says " 500 volts for all other ME EQUIPMENT and ME SYSTMS"
 

Peter Selvey

Staff member
Super Moderator
#5
For Roland: Control is not defined, but pretty obvious. For HF surgery, the finger switch would apply. But IEC 60601-2-2:2009 has a specific exclusion for this (see 201.8.10.4.1), so they obviously knew about this point.

For iutianyifly: seems you are mixing up rated input voltage (of the mains supply), with internal voltages. It's OK to have whatever internal voltages you want, as long as they are isolated or protected. Even a simple back light display can have 1000V to run the lamps (or at least they used to, before the blue LED :))
 
L

liutianyifly

#6
So, you mean, if it is carefully protected, the patients can hold a HV device, i.e,"back light display" for daily use?

If possible, could you tell me where I can find this in IEC60601? Because I have to convince my professor that my design is legal.
 

Peter Selvey

Staff member
Super Moderator
#7
There's no limit to secondary voltages in IEC 60601 (except for control devices).

But keep in mind there is a regulatory obligation and in risk management to use inherent protection where possible.

A back light display, for example, is HV but is also high frequency and current limited to a few mA. So, it's "high voltage" but not really dangerous to touch.

An ultrasound circuit is also HV but again is usually high frequency and current limited, so again not really dangerous to touch.

These designs are really inherently protected because the source of HV is current limited and/or high frequency.

If you want to have high power/current, low frequency, high voltage in a part which is intimately in contact with the patient, it is very dangerous and you need a really good reason for it.

Good design, risk management, common sense and regulations would require you to limit voltage and current as much as possible, irrespective of what is allowed in the standard.
 

Roland chung

Trusted Information Resource
#8
For Roland: Control is not defined, but pretty obvious. For HF surgery, the finger switch would apply. But IEC 60601-2-2:2009 has a specific exclusion for this (see 201.8.10.4.1), so they obviously knew about this point.
I am sorry to forget the exception in electrosurgical particular standard.

I have worked for a cosmetic light source (LS) equipment few years ago. The treatment head of LS equipment is hand-held that contains 12Vdc for fingerswitch and 12kV for igniting xenon lamp (very short time) and 400V for light exposure.

A new particular standard 60601-2-57 for LS equipment has been developed and published in 2011, unfortunately the particular mentions 8.10.4 of general standard applies to the hand-held parts. But the treatment head design is popular in the cosmetic industry.
 
L

liutianyifly

#9
Hi, Peter, thanks again the for information.
Basically, you are saying:

1 the power supply voltage is 250v for hand held device or 500v for others, 60v for controllers.

2 By using voltage regulator i.e, DC DC converter, you can use whatever high voltage you want.

3 However, this high voltage must be carefully protected. some protective method can be found in IEC 60601.

4 The ultrasonic transducer probe is something using HV inside and touch the human body. Therefore, my device (actually it is Avalanche photodiode, which needs HV to bias) can be used in the medical application as long as it is correctly shield and protected.

If I am misunderstanding something, please tell me, thanks very much.
 

Peter Selvey

Staff member
Super Moderator
#10
Sorry for the delay.

The term "mains" means (in effect) the connection to the supply in the wall, for example 230V socket. The clause that limits the "mains supply voltage" is for that connection point only, not the internal voltages in the equipment.

As we discussed, the clause for controls (hand/foot) limits to 60Vdc.

Other than that, any voltage is OK under IEC 60601-1 as long as it is properly protected.

Regulations, however, imply you should limit the HV current to the minimum needed for the application.
 
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