bigdad - really - do NOT use time outs for a three year old in meltdown. He is way too young to understand this punishment and will register it as punishment for having feelings. Instead, use the cosy corner technique which is effectively the same thing without any anger and guitl attached to it and with the added bonus of the child learning to self-regulate their emotions. You set up a cosy chair or toy tent or nest of cushions, with a blanket, soft toy, book and a drink. When they melt down, say with sympathy: You are very upset. You need some time to calm yourself down. Snuggle down and when you are feeling better, come and tell me. Love you.
Then leave them. If they come back rampaging, say, 'You still seem upset. Go back and curl up until you feel better.
It's so important that you don;t deny their right to having feelings but you equally don't put up with the meltdowns. You can say: I can't hear you when you scream at me and I need to make dinner/unpack the shopping etc so I will do my jobs and you snuggle up until you feel better. When you stop shouting you can tell me why you are upset.
It may seem wordy but it's kind and respcectful but you are still fully in control.
I hinestly think if you choose naughty-step/time out style punihsments instead, once this technique is known, you are setting your family up for emotional power struggles and battles that are wholly unnecessary. I have very strong willed children. So does a friend. She always used time outs and punishments, I used positive techniques. I had almost no toddler tantrums and meltdowns and no teenage strops - she's had endless hassle with both her DC all the way through because she insists on power struggles. They don't work. Take the battle away and without ever being a pushover, show love instead of authority.