[SWF]

I am using two Omron G3NAD210B solid state relays in my build, one to turn on the high voltage side of my DC/DC and one to turn on the KSI circuit on my curtis 1238 controller. I was doing some testing this weekend and found out that both of these have enough leakage current to partially or completely power their circuits before the relay is actually turned on.

In the case of the SSR controlling the DC/DC, the voltage that is passed by the relay starts about 10V but then gradually creeps up until it is high enough to turn on the DCDC. My system voltage is 96V nominal, and at full charge is about 114V.

For the SSR controlling the KSI power, there is enough leakage to completely power on the controller before activating the relay. This is really surprising as the controller is drawing much more than the relay specs list as the leakage current (5mA).

I've read of people putting high power resistors across the load side of the SSR to eliminate this problem, but wanted input on this problem before I go this route. Anyone else have similar problems with their SSRs?

Thanks

[mk4gti]

Is it possible that they failed? I hear they usually fail "turned on"

[SWF]

Originally Posted by mk4gti

Is it possible that they failed? I hear they usually fail "turned on"

It is possible, but they are rated to handle much higher current and voltage (10A/220VDC) than what they are exposed to in my system. They are both new, and I noticed before I installed them that the resistance across the load terminals was not as high as I would have expected (cannot recall exact value), so I was not too surprised to see that they were passing enough current to turn on the circuits they are controlling before activating the relay. From what I have read this is not uncommon with SSRs.

[cruisin]

Originally Posted by SWF

I am using two Omron G3NAD210B solid state relays in my build, one to turn on the high voltage side of my DC/DC and one to turn on the KSI circuit on my curtis 1238 controller. I was doing some testing this weekend and found out that both of these have enough leakage current to partially or completely power their circuits before the relay is actually turned on.

In the case of the SSR controlling the DC/DC, the voltage that is passed by the relay starts about 10V but then gradually creeps up until it is high enough to turn on the DCDC. My system voltage is 96V nominal, and at full charge is about 114V.

For the SSR controlling the KSI power, there is enough leakage to completely power on the controller before activating the relay. This is really surprising as the controller is drawing much more than the relay specs list as the leakage current (5mA).

I've read of people putting high power resistors across the load side of the SSR to eliminate this problem, but wanted input on this problem before I go this route. Anyone else have similar problems with their SSRs?

Thanks

You should not use a SSR for either one of the fuctions that you have installed them to control. If you PM me I can steer you to the right product to use. The SSR can fail very easy in the closed position.

[SWF]

Originally Posted by cruisin

You should not use a SSR for either one of the fuctions that you have installed them to control. If you PM me I can steer you to the right product to use. The SSR can fail very easy in the closed position.

Thanks for the input Cruisin. Would you be able to suggest to me here in this discussion which relay I should use? This may be useful for others who are trying to use SSRs for similar applications. I have seen others use SSRs for the KSI control, so I thought it would be OK. I would have preferred a mechanical relay, but could not find a good one that was rated to handle the voltage and current, other than going all the way up to a tyco contactor, which seemed like overkill.

[cruisin]

Originally Posted by SWF

Thanks for the input Cruisin. Would you be able to suggest to me here in this discussion which relay I should use? This may be useful for others who are trying to use SSRs for similar applications. I have seen others use SSRs for the KSI control, so I thought it would be OK. I would have preferred a mechanical relay, but could not find a good one that was rated to handle the voltage and current, other than going all the way up to a tyco contactor, which seemed like overkill.

For a starter you should use the relay that came with your HPEV system or Curtis controller. It is not rated for DC but I have not had one fail since using the new one currently available from HPEV dealers.

[SWF]

Originally Posted by cruisin

For a starter you should use the relay that came with your HPEV system or Curtis controller. It is not rated for DC but I have not had one fail since using the new one currently available from HPEV dealers.

I bought the controller and motor (AC20) used, and they did not come with a relay. Can you just tell me which relay is currently supplied?

[FWD]

is the controlller working? on this leakage voltage? or still shutdown.

if not then there is no problem! the voltage maybe high but when the controller really wanted to startup it would not do to because the current wil be 0.

[Lee Hart]

Originally Posted by SWF

Thanks for the input Cruisin. Would you be able to suggest to me here in this discussion which relay I should use? I would have preferred a mechanical relay, but could not find a good one that was rated to handle the voltage and current.

I agree with Crusin; these are not appropriate applications for an SSR (Solid State Relay). First, because they fail *on*, which is a bad or even dangerous condition. Second, because of the nature of the loads.

The KSI input is very low current; you would need a relay with a very low off-state leakage, and a rated carry current similar to the load you are actually switching, which is 50ma or less.

The DC/DC input has the problem of a huge peak inrush current. Most of them have large input filter capacitors, whose peak charging current can be 100 amps or more. SSRs are not good at handling such high peak currents.

I would consider something like a Schrack PT52A012B. This is a 4PDT relay with a 12vdc coil and contacts rated for 6a at 250vac or 30vdc, 40vdc at 1amp, 100vdc at 0.4a, and 300vdc at 0.25a. One source is www.digikey.com, PB1157-ND, $8.86 each.

The voltage rating of relay contacts in series add. This relay has 4 poles. Each by itself can only break 30vdc at 6 amps; but by wiring all 4 poles in series, you have a relay that can safely switch 30x4=120vdc at 6 amps. For most DC/DC converters, a 6amp rating is adequate.

If your DC/DC draws a huge current spike at turn-on (witnessed by a big spark when the relay contacts close), then you need to add an inrush limiter. Without one, no relay (mechanical or SSR) would last long. Inrush limiters are a little $1 part, also available from vendors like www.digikey.com.

For the KSI input, even a single pole of such a relay will work, because it is rated to switch low currents even at very high voltages. However, use a 2-pole relay anyway (such as a PT22A012B, the 2-pole version of the above). Connect KSI to the Common of both poles. Connect NC of one pole to B-, and NO of the other pole to to a fuse to whatever power source turns on the controller. Done this way, if the NO relay contact fails closed, you get a *short* when the relay turns off and the other pole shorts KSI to B-. This blows the fuse, guaranteeing that the power is off if the relay fails.

[SWF]

Many thanks Lee, this is very helpful. Using multiple relays crossed my mind at one point, but I never took the thought further and considered a multiple pole relay.

My DC/DC lists a typical inrush current of 60A, something I did not notice when I was going through the other specs. So I'll go ahead and also use an inrush limiter as you suggest.